Adafruit Feather RP2040 RFM69 User guide

Adafruit Feather RP2040 RFM69

Created by Kattni Rembor

https://learn.adafruit.com/feather-rp2040-rfm69

Last updated on 2023-05-04 06:52:23 PM EDT

©Adafruit Industries Page 1 of 215

Table of Contents

Overview

Pinouts

• Power Pins, Connections, and Charge LED

• Logic Pins

• GPIO Pins by Pin Functionality

• RFM69 Radio Module

• Antenna Connector and Pin

• Microcontroller and Flash

• Buttons and RST Pin

• NeoPixel and Red LED

• STEMMA QT

Antenna Options

• Wire Antenna

• uFL Antenna

Power Management

• Battery + USB Power

• Power Supplies

• Measuring Battery

• ENable pin

• Alternative Power Options

9

14

24

27

CircuitPython

• CircuitPython Quickstart

• Safe Mode

• Flash Resetting UF2

Installing the Mu Editor

• Download and Install Mu

• Starting Up Mu

• Using Mu

The CIRCUITPY Drive

• Boards Without CIRCUITPY

Creating and Editing Code

• Creating Code

• Editing Code

• Back to Editing Code...

• Naming Your Program File

Exploring Your First CircuitPython Program

• Imports & Libraries

• Setting Up The LED

• Loop-de-loops

• What Happens When My Code Finishes Running?

• What if I Don't Have the Loop?

31

35

37

38

43

©Adafruit Industries Page 2 of 215

Connecting to the Serial Console

• Are you using Mu?

• Serial Console Issues or Delays on Linux

• Setting Permissions on Linux

• Using Something Else?

46

Interacting with the Serial Console

The REPL

• Entering the REPL

• Interacting with the REPL

• Returning to the Serial Console

CircuitPython Libraries

• The Adafruit Learn Guide Project Bundle

• The Adafruit CircuitPython Library Bundle

• Downloading the Adafruit CircuitPython Library Bundle

• The CircuitPython Community Library Bundle

• Downloading the CircuitPython Community Library Bundle

• Understanding the Bundle

• Example Files

• Copying Libraries to Your Board

• Understanding Which Libraries to Install

• Example: ImportError Due to Missing Library

• Library Install on Non-Express Boards

• Updating CircuitPython Libraries and Examples

• CircUp CLI Tool

CircuitPython Documentation

• CircuitPython Core Documentation

• CircuitPython Library Documentation

49

52

57

68

Recommended Editors

• Recommended editors

• Recommended only with particular settings or add-ons

• Editors that are NOT recommended

Advanced Serial Console on Windows

• Windows 7 and 8.1

• What's the COM?

• Install Putty

Advanced Serial Console on Mac

• What's the Port?

• Connect with screen

Advanced Serial Console on Linux

• What's the Port?

• Connect with screen

• Permissions on Linux

Troubleshooting

• Always Run the Latest Version of CircuitPython and Libraries

• I have to continue using CircuitPython 5.x or earlier. Where can I find compatible libraries?

• Bootloader (boardnameBOOT) Drive Not Present

75

76

80

82

86

©Adafruit Industries Page 3 of 215

• Windows Explorer Locks Up When Accessing boardnameBOOT Drive

• Copying UF2 to boardnameBOOT Drive Hangs at 0% Copied

• CIRCUITPY Drive Does Not Appear or Disappears Quickly

• Device Errors or Problems on Windows

• Serial Console in Mu Not Displaying Anything

• code.py Restarts Constantly

• CircuitPython RGB Status Light

• CircuitPython 7.0.0 and Later

• CircuitPython 6.3.0 and earlier

• Serial console showing ValueError: Incompatible .mpy file

• CIRCUITPY Drive Issues

• Safe Mode

• To erase CIRCUITPY: storage.erase_filesystem()

• Erase CIRCUITPY Without Access to the REPL

• For the specific boards listed below:

• For SAMD21 non-Express boards that have a UF2 bootloader:

• For SAMD21 non-Express boards that do not have a UF2 bootloader:

• Running Out of File Space on SAMD21 Non-Express Boards

• Delete something!

• Use tabs

• On MacOS?

• Prevent & Remove MacOS Hidden Files

• Copy Files on MacOS Without Creating Hidden Files

• Other MacOS Space-Saving Tips

• Device Locked Up or Boot Looping

Frequently Asked Questions

• Using Older Versions

• Python Arithmetic

• Wireless Connectivity

• Asyncio and Interrupts

• Status RGB LED

• Memory Issues

• Unsupported Hardware

Welcome to the Community!

• Adafruit Discord

• CircuitPython.org

• Adafruit GitHub

• Adafruit Forums

• Read the Docs

CircuitPython Essentials

Blink

• LED Location

• Blinking an LED

RFM69 Radio Demo

• Load the Code and Libraries

• Receiver Code

• Sender Code

• RFM69 Radio Demo Usage

• Code Walkthrough

• NeoPixel Color Customisation

• Receive Demo Details

104

110

119

121

123

©Adafruit Industries Page 4 of 215

• Send Demo Details

Digital Input

• LED and Button

• Controlling the LED with a Button

Analog In

• Analog to Digital Converter (ADC)

• Potentiometers

• Hardware

• Wire Up the Potentiometer

• Reading Analog Pin Values

• Reading Analog Voltage Values

NeoPixel LED

• NeoPixel Location

• NeoPixel Color and Brightness

• RGB LED Colors

• NeoPixel Rainbow

Capacitive Touch

• One Capacitive Touch Pin

• Pin Wiring

• Reading Touch on the Pin

• Multiple Capacitive Touch Pins

• Pin Wiring

• Reading Touch on the Pins

• Where are my Touch-Capable pins?

131

133

139

145

I2C

• I2C and CircuitPython

• Necessary Hardware

• Wiring the MCP9808

• Find Your Sensor

• I2C Sensor Data

• Where's my I2C?

Storage

• The boot.py File

• The code.py File

• Logging the Temperature

• Recovering a Read-Only Filesystem

I2S

• I2S and CircuitPython

• Necessary Hardware

• Wiring the MAX98357A

• I2S Tone Playback

• I2S WAV File Playback

• CircuitPython I2S-Compatible Pin Combinations

asyncio

• asyncio Demonstration

• Wiring

• asyncio Example Code

150

158

163

168

©Adafruit Industries Page 5 of 215

• Code Walkthrough

• My program ended? What happened?

CPU Temperature

• Microcontroller Location

• Reading the Microcontroller Temperature

Arduino IDE Setup

• Arduino IDE Download

• Adding the Philhower Board Manager URL

• Add Board Support Package

• Choose Your Board

Arduino Usage

• RP2040 Arduino Pins

• Choose Your Board

• Load the Blink Sketch

• Manually Enter the Bootloader

Blink

• Pre-Flight Check: Get Arduino IDE & Hardware Set Up

• Start up Arduino IDE and Select Board/Port

• New Blink Sketch

• Verify (Compile) Sketch

• Upload Sketch

• Native USB and manual bootloading

• Enter Manual Bootload Mode

• Finally, a Blink!

176

178

181

183

Arduino I2C Scan

• Common I2C Connectivity Issues

• Perform an I2C scan!

• Wiring the MCP9808

Using the RFM69 Radio

• "Raw" vs Packetized

• Arduino Libraries

• RadioHead Library example

• Basic RX & TX example

• Basic Transmitter example code

• Basic receiver example code

• Radio Freq. Config

• Configuring Radio Pinout

• Setup

• Initializing Radio

• Basic Transmission Code

• Basic Receiver Code

• Basic Receiver/Transmitter Demo w/OLED

• Addressed RX and TX Demo

Factory Reset

• Step 1. Download the factory-reset.uf2 file

• Step 2. Enter RP2040 bootloader mode

• Step 3. Drag UF2 file to RPI-RP2

• Flash Resetting UF2

192

197

210

©Adafruit Industries Page 6 of 215

Radio Range F.A.Q.

212

Downloads

• Files:

• Schematic and Fab Print

214

©Adafruit Industries Page 7 of 215

©Adafruit Industries Page 8 of 215

Overview

This is theAdafruit Feather RP2040 RFM69 Packet Radio(868 or 915 MHz).We call

theseRadioFruits,our take on an microcontroller withpacket radio transceiver with

built-in USB and battery charging. It's an Adafruit Feather RP2040 with a RFM69HCW

900MHz radio module cooked in! Great for making wireless networks that are more

flexible than Bluetooth LE and without the high power requirements of WiFi.

Feather is thedevelopment board specificationfrom Adafruit, and like its namesake, it

is thin, light, and lets you fly! We designed Feather to be a new standard for portable

microcontroller cores.We have other boards in the Feather family, check'em out here

().

©Adafruit Industries Page 9 of 215

It's kinda like we took ourRP2040 Feather()andRFM69 900MHz breakout board()a

nd glued them together. You get all the pins for use on the Feather, the Lipoly battery

support, USB C power / data, onboard NeoPixel, 8MB of FLASH for storing code and

files, and then with the 8 unused pins, we wired up all the DIO pins on the RFM

module. There's even room left over for a STEMMA QT connector an a uFL connector

for connecting larger antennas.

This is the 900 MHz RFM69 packet radio version, which can be used for either

868MHz or 915MHz transmission/reception - the exact radio frequency is determined

when you load the software since it can be tuned around dynamically. Despite calling

it a 'packet' radio (and it does send packets of data) the RFM69 can also be used for

non-packetized radio transmission and reception.

©Adafruit Industries Page 10 of 215

At the Feather's heart is an RP2040 chip, clocked at 133 MHz and at 3.3V logic, the

same one used in theRaspberry Pi Pico(). This chip has a whopping 8MBof onboard

QSPI FLASH and 264K of RAM! This makes it great for making wireless sensor nodes

that can send to each other without a lot of software configuration.

To make it easy to use for portable projects, we added a connector for any of our 3.7V

Lithium polymer batteries and built-in battery charging. You don't need a battery, it will

run just fine straight from the USB Type C connector. But, if you do have a battery, you

can take it on the go, then plug in the USB to recharge. The Feather will automatically

switch over to USB power when its available.

Here'resome handy specs! You get:

Measures 52.2mm x 23.0mm x 7.3mm / 2.1" x 0.9" x 0.3" without headers

•

soldered in

Light as a (large?) feather - 6 grams

•

RP2040 32-bit Cortex M0+ dual core running at ~133 MHz @ 3.3V logic and

•

power

264 KB RAM

•

8 MB SPI FLASHchip for storing files and CircuitPython/MicroPython code

•

storage. No EEPROM

Tons of GPIO! 21 x GPIO pins with following capabilities:

•

Four12-bit ADCs (one more than Pico)

◦

Two I2C, Two SPI, and two UART peripherals, we label one for the 'main'

◦

interface in standard Feather locations

©Adafruit Industries Page 11 of 215

16 x PWM outputs - for servos, LEDs, etc

◦

Built-in 200mA+ lipoly chargerwith charging status indicator LED

•

Pin #13 red LEDfor general purpose blinking

•

RGB NeoPixelfor full-color indication.

•

On-boardSTEMMA QT connectorthat lets you quickly connect any Qwiic,

•

STEMMA QT or Grove I2C devices with no soldering!

Both Reset button and Bootloader select button for quick restarts(no

•

unplugging-replugging to relaunch code)

USB Type C connectorlets you access built-in ROM USB bootloader and serial

•

port debugging

3.3V Power/enable pin

•

4 mounting holes

•

12MHz crystal for perfect timing.

•

3.3V regulator with 500mA peak current output

•

We squished all the parts on our Feather RP2040 over towards the USB port to make

some roomon the end. ThisFeather RP2040 Packet Radiouses the extra space left

over to addan RFM69HCW high power868/915 MHz radio module. These radios are

not good for transmitting audio or video, but they do work quite well for small data

packet transmission when you need more range than 2.4 GHz (BT, BLE, WiFi, ZigBee).

Radio module specifications:

SX1231 based module with SPI interface

•

+13 to +20 dBm up to 100 mW Power Output Capability (power output selectable

•

in software)

©Adafruit Industries Page 12 of 215

50mA (+13 dBm) to 150mA (+20dBm) current draw for transmissions, ~30mA

•

during active radio listening.

Range of approx. 500 meters, depending on obstructions, frequency, antenna

•

and power output

Create multipoint networks with individual node addresses

•

Encrypted packet engine with AES-128

•

Packet radio with ready-to-go Arduino & CircuitPython libraries

•

Uses the license-free ISM band: "European ISM" @ 868MHz or "American ISM" @

•

915MHz

Simple wire antenna can be soldered into a solder pad, there's also auFL

•

connector that can be used with uFL-to-SMA adapters()for attaching bigger

antennas.

Our initial tests with default library settings indicate they can go at least 500 meters

line of sight using simple wire antennas, probably up to 5Km with directional antennas

and tweaking some settings.

Comes fully assembled and tested, we also toss in some headers so you can solder it

in and plug into a solderless breadboard. You will need to cut and solder on a small

piece of wire (any solid or stranded core is fine) in order to create your antenna. or

use a uFL connector and SMA 900MHz antenna.Lipoly battery and USB cable are not

included,but we do have lots of options in the shop if you'd like!

©Adafruit Industries Page 13 of 215

Pinouts

This Feather has a lot going on! This page details all of the pin-specific information

and various capabilities.

©Adafruit Industries Page 14 of 215

PrettyPins PDF on GitHub().

Power Pins, Connections, and Charge LED

USB C connector - This is used for power and data. Connect to your computer

•

via a USB C cable to update firmware and edit code.

LiPoly Battery connector- This 2-pin JST PH connector allows you to plug in

•

LiPoly batteries to power the Feather. The Feather is also capable of charging

batteries plugged into this port via USB.

chg LED - This small LED is located below the USB C connector. This indicates

•

the charge status of a connected LiPoly battery, if one is present and USB is

connected. It is amber while charging, and green when fully charged. Note, it's

©Adafruit Industries Page 15 of 215

normal for this LED to flicker when no battery is in place, that's the charge

circuitry trying to detect whether a battery is there or not.

GND - These are the common ground for all power and logic.

•

BAT - This is the positive voltage to/from the 2-pin JST PH jack for the optional

•

LiPoly battery.

USB - This is the positive voltage to/from the USB C connector, if USB is

•

connected.

EN - This is the 3.3V regulator's enable pin. It's pulled up, so connect to ground

•

to disable the 3.3V regulator.

3.3V - These pins are the output from the 3.3V regulator, they can supply

•

500mA peak.

Logic Pins

I2C and SPI on RP2040

The RP2040 is capable of handling I2C, SPI and UART on many pins. However, there

are really only two peripherals each of I2C, SPI and UART: I2C0 and I2C1, SPI0 and

SPI1, and UART0 and UART1. So while many pins are capable of I2C, SPI and UART,

©Adafruit Industries Page 16 of 215

you can only do two at a time, and only on separate peripherals, 0 and 1. I2C, SPI and

UART peripherals are included and numbered below.

PWM on RP2040

The RP2040 supports PWM on all pins. However, it is not capable of PWM on all pins

at the same time. There are 8 PWM "slices", each with two outputs, A and B. Each pin

on the Feather is assigned a PWM slice and output. For example, A0 is PWM5 A,

which means it is first output of the fifth slice. You can have up to 16 PWM objects on

this Feather. The important thing to know is that you cannot use the same slice and

output more than once at the same time. So, if you have a PWM object on pin A0, you

cannot also put a PWM object on D10, because they are both PWM5 A. The PWM

slices and outputs are indicated below. Note that PWM2 A and PWM3 B are not

available on the this Feather because not all pins are broken out.

Analog Pins

The RP2040 has four ADCs. These pins are the only pins capable of handling analog,

and they can also do digital.

A0/GP26 - This pin is ADC0. It is also SPI1 SCK, I2C1 SDA and PWM5 A.

•

A1/GP27 - This pin is ADC1. It is also SPI1 MOSI, I2C1 SCL and PWM5 B.

•

A2/GP28 - This pin is ADC2. It is also SPI1 MISO, I2C1 SDA and PWM6 A.

•

A3/GP29 - This pin is ADC3. It is also SPI1 CS, I2C0 SCL and PWM6 B.

•

Digital Pins

These are the digital I/O pins. They all have multiple capabilities.

D24/GPIO24 - Digital I/O pin 24. It is also UART1 TX, I2C0 SDA, and PWM4 A.

•

D25/GPIO25 - Digital I/O pin 25. It is also UART1 RX, I2C0 SCL, and PWM4 B.

•

SCK/GPIO14 - The main SPI1 SCK. It is also I2C1 SDA, and PWM7 A.

•

MO/GPIO15 - The main SPI1 MOSI. It is also I2C1 SCL, and PWM7 B.

•

MI/GPIO8 - The main SPI1 MISO. It is also UART1 TX, I2C0 SDA, and PWM4 A.

•

RX/GPIO1 - The main UART0 RX pin. It is also I2C0 SDA, SPI0 CS and PWM0 B.

•

TX/GPIO0 - The main UART0 TX pin. It is also I2C0 SCL, SPI0 MISO and PWM0

•

A.

D13/GPIO13 - Digital I/O pin 13. It is also SPI1 CS, UART0 RX, I2C0 SCL and

•

PWM6 B.

©Adafruit Industries Page 17 of 215

D12/GPIO12 - Digital I/O pin 12. It is also SPI1 MISO, UART0 TX, I2C0 SDA and

•

PWM6 A.

D11/GPIO11 - Digital I/O pin 11. It is also SPI1 MOSI, I2C1 SCL and PWM5 B.

•

D10/GPIO10 - Digital I/O pin 10. It is also SPI1 SCK, I2C1 SDA and PWM5 A.

•

D9/GPIO9 - Digital I/O pin 9. It is also SPI1 CS, UART1 RX, I2C0 SCL and PWM4

•

B.

D6/GPIO6 - Digital I/O pin 6. It is also SPI0 SCK, I2C1 SDA, and PWM3 A.

•

D5/GPIO5 - Digital I/O pin 5. It is also SPI0 CS, UART1 RX, I2C0 SCL, and PWM2

•

B.

SCL/GP03 - The main I2C1 clock pin. It is also SPI0 MOSI, I2C1 SCL and PWM1 B.

•

SDA/GP02 - The main I2C1 data pin. It is also SPI0 SCK, I2C1 SDA and PWM1 A.

•

CircuitPython I2C, SPI and UART

Note that in CircuitPython, there is a board object each for STEMMA QT, I2C, SPI and

UART that use the connector and pins labeled on the Feather. You can use these

objects to initialise these peripherals in your code.

board.STEMMA_I2C() uses the STEMMA QT connector (in this case, SCL/SDA

•

pins)

board.I2C() uses SCL/SDA pins

•

board.SPI() uses SCK/MO/MI pins

•

board.UART() uses RX/TX pins

•

GPIO Pins by Pin Functionality

Primary pins based on the silkscreen pin labels are bold.

I2C Pins

I2C0 SCL: A3, D25, RX, D13, D9, D5

•

I2C0 SDA: A2, D24, MISO, TX, D12

•

I2C1 SCL: SCL, A1, MOSI, D11

•

I2C1 SDA: SDA, A0, SCK, D10, D6

•

SPI Pins

SPI0 SCK: D6, SDA

•

SPI0 MOSI: SCL

•

SPI0 MISO: TX

•

©Adafruit Industries Page 18 of 215

SPI0 CS: RX, D5

•

SPI1 SCK: SCK, A0, D10

•

SPI1 MOSI: MOSI, A1, D11

•

SPI1 MISO: MISO, A2, D24, D12

•

SPI1 CS: A3, D25, D13, D9

•

UART Pins

UART0 TX: TX, A2, D12

•

UART0 RX: RX, A3, D13

•

UART1 TX: D24, MISO

•

UART1 RX: D25, D9, D5

•

PWM Pins

PWM0 A: TX

•

PWM0 B: RX

•

PWM1 A: SDA

•

PWM1 B: SCL

•

PWM2 A: (none)

•

PWM2 B: D5

•

PWM3 A: D6

•

PWM3 B: (none)

•

PWM4 A: D24, MISO

•

PWM4 B: D25, D9

•

PWM5 A: A0, D10

•

PWM5 B: A1, D11

•

PWM6 A: A2, D12

•

PWM6 B: A3, D13

•

PWM7 A: SCK

•

PWM7 B: MOSI

•

©Adafruit Industries Page 19 of 215

RFM69 Radio Module

This Feather has an RFM69HCW high power 868/915 MHz radio module built right in.

This radio is not good for transmitting audio or video, but it does work quite well for

small data packet transmission when you need more range than 2.4 GHz (BT, BLE,

WiFi, ZigBee). It is an SX1231 based module with SPI interface.

The radio module has a chip select and reset pin.

The RFM chip select pin is available as RFM_CS in CircuitPython, and PIN_RFM_

•

CS in Arduino.

The RFM reset pin is available as RFM_RST in CircuitPython, and PIN_RFM_RST

•

in Arduino.

There are also six IO pins.

Pin 0 is available as RFM_IO0 in CircuitPython, and PIN_RFM_DIO0 in Arduino.

•

Pin 1 is available as RFM_IO1 in CircuitPython, and PIN_RFM_DIO1 in Arduino.

•

Pin 2 is available as RFM_IO2 in CircuitPython, and PIN_RFM_DIO2 in Arduino.

•

Pin 3 is available as RFM_IO3 in CircuitPython, and PIN_RFM_DIO3 in Arduino.

•

Pin 4 is available as RFM_IO4 in CircuitPython, and PIN_RFM_DIO4 in Arduino.

•

Pin 5 is available as RFM_IO5 in CircuitPython, and PIN_RFM_DIO5 in Arduino.

•

©Adafruit Industries Page 20 of 215

Antenna Connector and Pin

On the right side oft the board, above center, is a uFL connector that can be used

with uFL-to-SMA adapters()for attaching bigger antennas.

Immediately above the connector is the ANT through-hole pad, which makes it

possible to add a simple wire antenna by soldering it in.

Microcontroller and Flash

The large square towards the middle is the RP2040 microcontroller, the "brains" of

this Feather board.

The square towards the top-middle is the QSPI Flash. It is connected to 6 pins that are

not brought out on the GPIO pads. This way you don't have to worry about the SPI

flash colliding with other devices on the main SPI connection.

QSPI is neat because it allows you to have 4 data in/out lines instead of just SPI's

single line in and single line out. This means that QSPI is at least 4 times faster. But in

©Adafruit Industries Page 21 of 215

reality is at least 10x faster because you can clock the QSPI peripheral much faster

than a plain SPI peripheral.

Buttons and RST Pin

The Boot button is the button on the right. It is available as board.BOOT in
CircuitPython, and is available for use in Arduino as PIN_BUTTON . It is also used to

enter the bootloader. To enter the bootloader, press and hold Boot and then power up

the board (either by plugging it into USB or pressing Reset). The bootloader is used to

install/update CircuitPython.

The Reset buttonis on the left. It restarts the board and helps enter the bootloader.

You can click it to reset the board without unplugging the USB cable or battery.

The RST pin can be used to reset the board. Tie to ground manually to reset the

board.

NeoPixel and Red LED

©Adafruit Industries Page 22 of 215

Above the pin labels for D24 and D25 is the status NeoPixel LED. In CircuitPython, the
NeoPixel is available at board.NEOPIXEL and the library for it is available in the

bundle(). In Arduino, it is accessible at PIN_NEOPIXEL . The NeoPixel is powered by

the 3.3V power supply but that hasn't shown to make a big difference in brightness or

color. In CircuitPython, the LED is used to indicate the runtime status.

Above the USB C connector is the D13 LED. This little red LED is controllable in
CircuitPython code using board.LED , and in Arduino as PIN_LED . Also, this LED will

pulse when the board is in bootloader mode.

STEMMA QT

On the far right of the board, below the antenna connector, is the STEMMA QT

connector! This means you can connect up all sorts of I2C sensors and breakouts(),

no soldering required! This connector uses the SCL and SDA pins for I2C, which end

up being the RP2040's I2C1 peripheral. In CircuitPython, you can initialise the
STEMMA connector with board.STEMMA_I2C() (as well as with board.SCL / board.

SDA ). In Arduino it is Wire .

STEMMA QT / Qwiic JST SH 4-pin Cable -

100mm Long

This 4-wire cable is a little over 100mm /

4" long and fitted with JST-SH female 4-

pin connectors on both ends. Compared

with the chunkier JST-PH these are 1mm

pitch instead of...

https://www.adafruit.com/product/4210

©Adafruit Industries Page 23 of 215

Antenna Options

Your Feather Radio does not have a built-in antenna. Instead, you have two options

for attaching an antenna. For most low cost radio nodes, a short length of wire works

great. If you need to put the Feather into an enclosure, soldering on a uFL connector

(on Feathers that don’t already include this) and using a uFL to SMA adapter will let

you attach an external antenna.

Wire Antenna

A wire antenna, aka "quarter wave whip antenna" is low cost and works very well! You

just have to cut the wire down to the right length.

Cut a stranded or solid core wire to the

proper length for the module/frequency:

433 MHz - 6.5 inches, or 16.5 cm

868 MHz - 3.25 inches or 8.2 cm

915 MHz - 3 inches or 7.8 cm

Strip a mm or two off the end of the wire,

tin and solder into the ANT pad on the

very right hand edge of the Feather.

©Adafruit Industries Page 24 of 215

That's pretty much it, you're done!

uFL Antenna

If you want an external antenna, you need to do a tiny bit more work but its not too

difficult.

For Feather Radio boards that don’t already have a surface-mount uFL connector

installed, you’ll need to get one(http://adafru.it/1661). Feather RP2040 RFM boards

already have this installed. Feather M0 and 32u4 require soldering.

You'll also need a uFL to SMA adapter(http://adafru.it/851) (or whatever adapter you

need for the antenna you'll be using, SMA is the most common).

Of course, you will also need an antenna of some sort, one that matches your radio

frequency.

uFL connectors are rated for 30 connection cycles, but be careful when

connecting/disconnecting to not rip the pads off the PCB. Once a uFL/SMA

adapter is connected, use strain relief!

For Feather M0 and 32u4:

(this step can be skipped for Feather RP2040 RFM, which already has a uFL

connector installed)

©Adafruit Industries Page 25 of 215

Check the bottom of the uFL connector,

note that there's two large side pads

(ground) and a little inlet pad. The other

small pad is not used!

Solder all three pads to the bottom of the

Feather

©Adafruit Industries Page 26 of 215

For all radio-capable Feather boards:

Power Management

Once done attach your uFL adapter and

antenna!

Battery + USB Power

We wanted to make our Feather boards easy to power both when connected to a

computer as well as via battery.

There's two ways to power a Feather:

You can connect with a USB cable (just plug into the jack) and the Feather will

1.

regulate the 5V USB down to 3.3V.

©Adafruit Industries Page 27 of 215

You can also connect a 4.2/3.7V Lithium Polymer (LiPo/LiPoly) or Lithium Ion

2.

(LiIon) battery to the JST jack. This will let the Feather run on a rechargeable

battery.

When the USB power is powered, it will automatically switch over to USB for power,

as well as start charging the battery (if attached). This happens 'hot-swap' style so you

can always keep the LiPoly connected as a 'backup' power that will only get used

when USB power is lost.

The JST connector polarity is matched to Adafruit LiPoly batteries. Using wrong

polarity batteries can destroy your Feather. Many customers try to save money

by purchasing Lipoly batteries from Amazon only to find that they plug them in

and the Feather is destroyed!

The above shows the USB C connector (left center), the chg LED (below the USB C

connector), the LiPoly JST connector (top left), as well as the changeover diode (to the

left of the JST jack), the 3.3V regulators (to the left of the JST connector and the USB

C connector), and the charging circuitry (below the JST connector).

There's also a CHG LED next to the USB jack, which will light up while the battery is

charging. This LED might also flicker if the battery is not connected, it's normal.

The charge LED is automatically driven by the LiPoly charger circuit. It will try to

detect a battery and is expecting one to be attached. If there isn't one it may

flicker once in a while when you use power because it's trying to charge a (non-

existent) battery. It's not harmful, and its totally normal!

©Adafruit Industries Page 28 of 215

Power Supplies

You have a lot of power supply options here! We bring out the BAT pin, which is tied

to the LiPoly JST connector, as well as USB which is the +5V from USB if connected.

We also have the 3V pin which has the output from the 3.3V regulator. We use a

500mA peak regulator. While you can get 500mA from it, you can't do it continuously

from 5V as it will overheat the regulator.

Measuring Battery

If you're running off of a battery, chances are you wanna know what the voltage is at!

That way you can tell when the battery needs recharging. LiPoly batteries are 'maxed

out' at 4.2V and stick around 3.7V for much of the battery life, then slowly sink down

to 3.2V or so before the protection circuitry cuts it off. By measuring the voltage you

can quickly tell when you're heading below 3.7V.

Note that unlike other Feathers, we do not have an ADC connected to a battery

monitor. Reason being there's only 4 ADCs and we didn't want to use one precious

ADC for a battery monitor. You can create a resistor divider from BAT to GND with two

10K resistors and connect the middle to one of the ADC pins on a breadboard.

ENable pin

If you'd like to turn off the 3.3V regulator, you can do that with the EN(able) pin. Simply

tie this pin to Ground and it will disable the 3V regulator. The BAT and USB pins will

still be powered.

©Adafruit Industries Page 29 of 215

STEMMA QT Power

This Feather is equipped with a STEMMA QT port. Unlike anything controlled by the

ENable pin, this is controlled by GPIO. STEMMA QT power is connected to 3.3V.

Alternative Power Options

The two primary ways for powering a feather are a 3.7/4.2V LiPo battery plugged into

the JST port or a USB power cable.

If you need other ways to power the Feather, here's what we recommend:

For permanent installations, a 5V 1A USB wall adapter() will let you plug in a

•

USB cable for reliable power

For mobile use, where you don't want a LiPoly, use a USB battery pack!()

•

If you have a higher voltage power supply, use a 5V buck converter() and wire it

•

to a USB cable's 5V and GND input()

©Adafruit Industries Page 30 of 215

Here's what you cannot do:

Do not use alkaline or NiMH batteries and connect to the battery port - this will

•

destroy the LiPoly charger and there's no way to disable the charger

Do not use 7.4V RC batteries on the battery port - this will destroy the board

•

The Feather is not designed for external power supplies - this is a design decision to

make the board compact and low cost. It is not recommended, but technically

possible:

Connect an external 3.3V power supply to the 3V and GND pins. Not

•

recommended, this may cause unexpected behavior and the EN pin will no

longer work. Also this doesn't provide power on BAT or USB and some

Feathers/Wings use those pins for high current usages. You may end up

damaging your Feather.

Connect an external 5V power supply to the USB and GND pins. Not

•

recommended, this may cause unexpected behavior when plugging in the USB

port because you will be back-powering the USB port, which could confuse or

damage your computer.

CircuitPython

CircuitPython() is a derivative of MicroPython() designed to simplify experimentation

and education on low-cost microcontrollers. It makes it easier than ever to get

prototyping by requiring no upfront desktop software downloads. Simply copy and

edit files on the CIRCUITPY drive to iterate.

CircuitPython Quickstart

Follow this step-by-step to quickly get CircuitPython running on your board.

Download the latest version of

CircuitPython for this board via

circuitpython.org

©Adafruit Industries Page 31 of 215

Click the link above to download the latest

CircuitPython UF2 file.

Save it wherever is convenient for you.

To enter the bootloader, hold down the BOOT/BOOTSEL button (highlighted in red

above), and while continuing to hold it (don't let go!), press and release the reset

button (highlighted in blue above). Continue to hold the BOOT/BOOTSEL button until

the RPI-RP2 drive appears!

If the drive does not appear, release all the buttons, and then repeat the process

above.

You can also start with your board unplugged from USB, press and hold the BOOTSEL

button (highlighted in red above), continue to hold it while plugging it into USB, and

wait for the drive to appear before releasing the button.

A lot of people end up using charge-only USB cables and it is very frustrating! Make

sure you have a USB cable you know is good for data sync.

©Adafruit Industries Page 32 of 215

You will see a new disk drive appear called

RPI-RP2.



Drag the adafruit_circuitpython_etc.uf2 file

to RPI-RP2.

The RPI-RP2 drive will disappear and a

new disk drive called CIRCUITPY will

appear.

That's it, you're done! :)

Safe Mode

You want to edit your code.py or modify the files on your CIRCUITPY drive, but find

that you can't. Perhaps your board has gotten into a state where CIRCUITPY is read-

only. You may have turned off the CIRCUITPY drive altogether. Whatever the reason,

safe mode can help.

©Adafruit Industries Page 33 of 215

Safe mode in CircuitPython does not run any user code on startup, and disables auto-

reload. This means a few things. First, safe mode bypasses any code in boot.py

(where you can set CIRCUITPY read-only or turn it off completely). Second, it does not

run the code in code.py. And finally, it does not automatically soft-reload when data is

written to the CIRCUITPY drive.

Therefore, whatever you may have done to put your board in a non-interactive state,

safe mode gives you the opportunity to correct it without losing all of the data on the

CIRCUITPY drive.

Entering Safe Mode

To enter safe mode when using CircuitPython, plug in your board or hit reset

(highlighted in red above). Immediately after the board starts up or resets, it waits

1000ms. On some boards, the onboard status LED (highlighted in green above) will

blink yellow during that time. If you press reset during that 1000ms, the board will

start up in safe mode. It can be difficult to react to the yellow LED, so you may want to

think of it simply as a slow double click of the reset button. (Remember, a fast double

click of reset enters the bootloader.)

In Safe Mode

If you successfully enter safe mode on CircuitPython, the LED will intermittently blink

yellow three times.

If you connect to the serial console, you'll find the following message.

Auto-reload is off.
Running in safe mode! Not running saved code.

CircuitPython is in safe mode because you pressed the reset button during boot.
Press again to exit safe mode.

Press any key to enter the REPL. Use CTRL-D to reload.

You can now edit the contents of the CIRCUITPY drive. Remember, your code will not

run until you press the reset button, or unplug and plug in your board, to get out of

safe mode.

©Adafruit Industries Page 34 of 215

Flash Resetting UF2

If your board ever gets into a really weird state and doesn't even show up as a disk

drive when installing CircuitPython, try loading this 'nuke' UF2 which will do a 'deep

clean' on your Flash Memory. You will lose all the files on the board, but at least you'll

be able to revive it! After loading this UF2, follow the steps above to re-install

CircuitPython.

Download flash erasing "nuke" UF2

Installing the Mu Editor

Mu is a simple code editor that works with the Adafruit CircuitPython boards. It's

written in Python and works on Windows, MacOS, Linux and Raspberry Pi. The serial

console is built right in so you get immediate feedback from your board's serial

output!

Mu is our recommended editor - please use it (unless you are an experienced

coder with a favorite editor already!).

Download and Install Mu

Download Mu fromhttps://codewith.mu().

Click theDownload link for downloads and

installation instructions.

Click Start Hereto find a wealth of other

information, including extensive tutorials

and and how-to's.



Windows users: due to the nature of MSI installers, please remove old versions of

Mu before installing the latest version.

Ubuntu users: Mu currently (checked May 4, 2022) does not install properly on

Ubuntu 22.04. See https://github.com/mu-editor/mu/issues to track this issue.

©Adafruit Industries Page 35 of 215

See https://learn.adafruit.com/welcome-to-circuitpython/recommended-editors

and https://learn.adafruit.com/welcome-to-circuitpython/pycharm-and-

circuitpython for other editors to use.

Starting Up Mu

The first time you start Mu, you will be

prompted to select your 'mode' - you can

always change your mind later. For now

please select CircuitPython!

The current mode is displayed in the lower

right corner of the window, next to the

"gear" icon. If the mode says "Microbit" or

something else, click the Mode button in

the upper left, and then choose

"CircuitPython" in the dialog box that

appears.

Mu attempts to auto-detect your board on

startup, so if you do not have a

CircuitPython board plugged in with a

CIRCUITPY drive available, Mu will inform

you where it will store any code you save

until you plug in a board.

To avoid this warning, plug in a board and

ensure that the CIRCUITPY drive is

mounted before starting Mu.

Using Mu

You can now explore Mu! The three main sections of the window are labeled below;

the button bar, the text editor, and the serial console / REPL.

©Adafruit Industries Page 36 of 215

Now you're ready to code! Let's keep going...

The CIRCUITPY Drive

When CircuitPython finishes installing, or you plug a CircuitPython board into your

computer with CircuitPython already installed, the board shows up on your computer

as a USB drive called CIRCUITPY.

The CIRCUITPY drive is where your code and the necessary libraries and files will live.

You can edit your code directly on this drive and when you save, it will run

automatically. When you create and edit code, you'll save your code in a code.py file

located on the CIRCUITPY drive.If you're following along with a Learn guide, you can

paste the contents of the tutorial example into code.py on the CIRCUITPY drive and

save it to run the example.

With a fresh CircuitPython install, on your CIRCUITPY drive, you'll find a code.py file
containing print("Hello World!") and an empty lib folder. If your CIRCUITPY

drive does not contain a code.py file, you can easily create one and save it to the

drive. CircuitPython looks for code.py and executes the code within the file

automatically when the board starts up or resets. Following a change to the contents

of CIRCUITPY, such as making a change to the code.py file, the board will reset, and

the code will be run. You do not need to manually run the code. This is what makes it

so easy to get started with your project and update your code!

Note that all changes to the contents of CIRCUITPY, such as saving a new file,

renaming a current file, or deleting an existing file will trigger a reset of the board.

©Adafruit Industries Page 37 of 215

Boards Without CIRCUITPY

CircuitPython is available for some microcontrollers that do not support native USB.

Those boards cannot present a CIRCUITPY drive. This includes boards using ESP32

or ESP32-C3 microcontrollers.

On these boards, there are alternative ways to transfer and edit files. You can use the

Thonny editor(), which uses hidden commands sent to the REPL to read and write

files. Or you can use the CircuitPython web workflow, introduced in Circuitpython 8.

The web workflow provides browser-based WiFi access to the CircuitPython

filesystem. These guides will help you with the web workflow:

CircuitPython on ESP32 Quick Start()

•

CircuitPython Web Workflow Code Editor Quick Start()

•

Creating and Editing Code

One of the best things about CircuitPython is how simple it is to get code up and

running. This section covers how to create and edit your first CircuitPython program.

To create and edit code, all you'll need is an editor. There are many options. Adafruit

strongly recommends using Mu! It's designed for CircuitPython, and it's really simple

and easy to use, with a built in serial console!

If you don't or can't use Mu, there are a number of other editors that work quite well.

The Recommended Editors page() has more details. Otherwise, make sure you do

"Eject" or "Safe Remove" on Windows or "sync" on Linux after writing a file if you

aren't using Mu. (This is not a problem on MacOS.)

©Adafruit Industries Page 38 of 215

Creating Code

Installing CircuitPython generates a

code.py file on your CIRCUITPY drive. To

begin your own program, open your editor,

and load the code.py file from the

CIRCUITPY drive.

If you are using Mu, click the Load button

in the button bar, navigate to the

CIRCUITPY drive, and choose code.py.

Copy and paste the following code into your editor:

import board
import digitalio
import time

led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

while True:
led.value = True
time.sleep(0.5)
led.value = False
time.sleep(0.5)

The KB2040, QT Py and the Trinkeys do not have a built-in little red LED! There is

an addressable RGB NeoPixel LED. The above example will NOT work on the

KB2040, QT Py or the Trinkeys!

If you're using a KB2040, QT Py or a Trinkey, please download the NeoPixel blink

example().

The NeoPixel blink example uses the onboard NeoPixel, but the time code is the

same. You can use the linked NeoPixel Blink example to follow along with this

guide page.

©Adafruit Industries Page 39 of 215

It will look like this. Note that under the

while True: line, the next four lines

begin with four spaces to indent them, and

they're indented exactly the same amount.

All the lines before that have no spaces

before the text.

Save the code.py file on your CIRCUITPY

drive.

The little LED should now be blinking. Once per half-second.

Congratulations, you've just run your first CircuitPython program!

On most boards you'll find a tiny red LED.

On the ItsyBitsy nRF52840, you'll find a tiny blue LED.

On QT Py M0, QT Py RP2040, and the Trinkey series, you will find only an RGB

NeoPixel LED.

©Adafruit Industries Page 40 of 215

Editing Code

To edit code, open thecode.pyfile on your

CIRCUITPY drive into your editor.



Make the desired changes to your code.

Save the file. That's it!

Your code changes are run as soon as the file is done saving.

There's one warning before you continue...

Don't click reset or unplug your board!

The CircuitPython code on your board detects when the files are changed or written

and will automatically re-start your code. This makes coding very fast because you

save, and it re-runs. If you unplug or reset the board before your computer finishes

writing the file to your board, you can corrupt the drive. If this happens, you may lose

the code you've written, so it's important to backup your code to your computer

regularly.

There are a couple of ways to avoid filesystem corruption.

1. Use an editor that writes out the file completely when you save it.

Check out the Recommended Editors page() for details on different editing options.

If you are dragging a file from your host computer onto the CIRCUITPY drive, you

still need to do step 2. Eject or Sync (below) to make sure the file is completely

written.

©Adafruit Industries Page 41 of 215

2. Eject or Sync the Drive After Writing

If you are using one of our not-recommended-editors, not all is lost! You can still make

it work.

On Windows, you can Eject or Safe Remove the CIRCUITPY drive. It won't actually

eject, but it will force the operating system to save your file to disk. On Linux, use the

sync command in a terminal to force the write to disk.

You also need to do this if you use Windows Explorer or a Linux graphical file

manager to drag a file onto CIRCUITPY.

Oh No I Did Something Wrong and Now The CIRCUITPY Drive Doesn't Show Up!!!

Don't worry! Corrupting the drive isn't the end of the world (or your board!). If this

happens, follow the steps found on the Troubleshooting() page of every board

guide to get your board up and running again.

Back to Editing Code...

Now! Let's try editing the program you added to your board. Open your code.py file
into your editor. You'll make a simple change. Change the first 0.5 to 0.1 . The code

should look like this:

import board
import digitalio
import time

led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

while True:
led.value = True
time.sleep(0.1)
led.value = False
time.sleep(0.5)

Leave the rest of the code as-is. Save your file. See what happens to the LED on your

board? Something changed! Do you know why?

You don't have to stop there! Let's keep going. Change the second 0.5 to 0.1 so it

looks like this:

©Adafruit Industries Page 42 of 215

while True:
led.value = True
time.sleep(0.1)
led.value = False
time.sleep(0.1)

Now it blinks really fast! You decreased the both time that the code leaves the LED on

and off!

Now try increasing both of the 0.1 to 1 . Your LED will blink much more slowly

because you've increased the amount of time that the LED is turned on and off.

Well done! You're doing great! You're ready to start into new examples and edit them

to see what happens! These were simple changes, but major changes are done using

the same process. Make your desired change, save it, and get the results. That's

really all there is to it!

Naming Your Program File

CircuitPython looks for a code file on the board to run. There are four options: code.tx

t, code.py, main.txt and main.py. CircuitPython looks for those files, in that order, and

then runs the first one it finds. While code.py is the recommended name for your code

file, it is important to know that the other options exist. If your program doesn't seem

to be updating as you work, make sure you haven't created another code file that's

being read instead of the one you're working on.

Exploring Your First CircuitPython Program

First, you'll take a look at the code you're editing.

Here is the original code again:

import board
import digitalio
import time

led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

while True:
led.value = True
time.sleep(0.5)
led.value = False
time.sleep(0.5)

©Adafruit Industries Page 43 of 215

Imports & Libraries

Each CircuitPython program you run needs to have a lot of information to work. The

reason CircuitPython is so simple to use is that most of that information is stored in

other files and works in the background. The files built into CircuitPython are called m

odules, and the files you load separately are called libraries. Modules are built into

CircuitPython. Libraries are stored on your CIRCUITPY drive in a folder called lib.

import board
import digitalio
import time

The import statements tells the board that you're going to use a particular library or
module in your code. In this example, you imported three modules: board ,

digitalio , and time . All three of these modules are built into CircuitPython, so no

separate library files are needed. That's one of the things that makes this an excellent

first example. You don't need anything extra to make it work!

These three modules each have a purpose. The first one, board , gives you access to
the hardware on your board. The second, digitalio , lets you access that hardware
as inputs/outputs.The third, time , let's you control the flow of your code in multiple

ways, including passing time by 'sleeping'.

Setting Up The LED

The next two lines setup the code to use the LED.

led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

Your board knows the red LED as LED . So, you initialise that pin, and you set it to
output. You set led to equal the rest of that information so you don't have to type it

all out again later in our code.

Loop-de-loops

The third section starts with a while statement. while True: essentially means,
"forever do the following:". while True: creates a loop. Code will loop "while" the
condition is "true" (vs. false), and as True is never False, the code will loop forever.
All code that is indented under while True: is "inside" the loop.

©Adafruit Industries Page 44 of 215

Inside our loop, you have four items:

while True:
led.value = True
time.sleep(0.5)
led.value = False
time.sleep(0.5)

First, you have led.value = True . This line tells the LED to turn on. On the next
line, you have time.sleep(0.5) . This line is telling CircuitPython to pause running

code for 0.5 seconds. Since this is between turning the led on and off, the led will be

on for 0.5 seconds.

The next two lines are similar. led.value = False tells the LED to turn off, and tim

e.sleep(0.5) tells CircuitPython to pause for another 0.5 seconds. This occurs

between turning the led off and back on so the LED will be off for 0.5 seconds too.

Then the loop will begin again, and continue to do so as long as the code is running!

So, when you changed the first 0.5 to 0.1 , you decreased the amount of time that

the code leaves the LED on. So it blinks on really quickly before turning off!

Great job! You've edited code in a CircuitPython program!

What Happens When My Code Finishes Running?

When your code finishes running, CircuitPython resets your microcontroller board to

prepare it for the next run of code. That means any set up you did earlier no longer

applies, and the pin states are reset.

For example, try reducing the code snippet above by eliminating the loop entirely,
and replacing it with led.value = True . The LED will flash almost too quickly to

see, and turn off. This is because the code finishes running and resets the pin state,

and the LED is no longer receiving a signal.

To that end, most CircuitPython programs involve some kind of loop, infinite or

otherwise.

©Adafruit Industries Page 45 of 215

What if I Don't Have the Loop?

If you don't have the loop, the code will run to the end and exit. This can lead to some

unexpected behavior in simple programs like this since the "exit" also resets the state

of the hardware. This is a different behavior than running commands via REPL. So if

you are writing a simple program that doesn't seem to work, you may need to add a

loop to the end so the program doesn't exit.

The simplest loop would be:

while True:
pass

And remember - you can press CTRL+C to exit the loop.

See also the Behavior section in the docs().

Connecting to the Serial Console

One of the staples of CircuitPython (and programming in general!) is something called

a "print statement". This is a line you include in your code that causes your code to

output text. A print statement in CircuitPython (and Python) looks like this:

print("Hello, world!")

This line in your code.py would result in:

Hello, world!

However, these print statements need somewhere to display. That's where the serial

console comes in!

The serial console receives output from your CircuitPython board sent over USB and

displays it so you can see it. This is necessary when you've included a print statement

in your code and you'd like to see what you printed. It is also helpful for

troubleshooting errors, because your board will send errors and the serial console will

display those too.

The serial console requires an editor that has a built in terminal, or a separate

©Adafruit Industries Page 46 of 215

terminal program. A terminal is a program that gives you a text-based interface to

perform various tasks.

Are you using Mu?

If so, good news! The serial consoleis built into Mu and willautodetect your board

making using the serial console really really easy.

First, make sure your CircuitPython board

is plugged in.

If you open Mu without a board plugged

in, you may encounter the error seen here,

letting you know no CircuitPython board

was found and indicating where your code

will be stored until you plug in a board.

If you are using Windows 7, make sure you

installed the drivers().

Once you've opened Mu with your board plugged in, look for the Serial button in the

button bar and click it.

The Mu window will split in two, horizontally, and display the serial console at the

bottom.

If nothing appears in the serial console, it may mean your code is done running

or has no print statements in it. Click into the serial console part of Mu, and press

CTRL+D to reload.

©Adafruit Industries Page 47 of 215

Serial Console Issues or Delays on Linux

If you're on Linux, and are seeing multi-second delays connecting to the serial

console, or are seeing "AT" and other gibberish when you connect, then the

modemmanager service might be interfering. Just remove it; it doesn't have much use

unless you're still using dial-up modems.

To remove modemmanager , type the following command at a shell:

sudo apt purge modemmanager

Setting Permissions on Linux

On Linux, if you see an error box something like the one below when you press the S

erial button, you need to add yourself to a user group to have permission to connect

to the serial console.

On Ubuntu and Debian, add yourself to the dialout group by doing:

sudo adduser $USER dialout

After running the command above, reboot your machine to gain access to the group.

On other Linux distributions, the group you need may be different. See the Advanced

Serial Console on Linux()for details on how to add yourself to the right group.

Using Something Else?

If you're not using Mu to edit, are using or if for some reason you are not a fan of its

built in serial console, you can run the serial console from a separate program.

©Adafruit Industries Page 48 of 215

Windows requires you to download a terminal program. Check out the Advanced

Serial Console on Windows page for more details.()

MacOS has Terminal built in, though there are other options available for download. C

heck the Advanced Serial Console on Mac page for more details.()

Linux has a terminal program built in, though other options are available for

download. Check the Advanced Serial Console on Linux page for more details.()

Once connected, you'll see something like the following.

Interacting with the Serial Console

Once you've successfully connected to the serial console, it's time to start using it.

The code you wrote earlier has no output to the serial console. So, you're going to

edit it to create some output.

Open your code.py file into your editor, and include a print statement. You can print

anything you like! Just include your phrase between the quotation marks inside the

parentheses. For example:

import board
import digitalio
import time

led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

while True:
print("Hello, CircuitPython!")
led.value = True
time.sleep(1)
led.value = False
time.sleep(1)

Save your file.

Now, let's go take a look at the window with our connection to the serial console.

©Adafruit Industries Page 49 of 215

Excellent! Our print statement is showing up in our console! Try changing the printed

text to something else.

import board
import digitalio
import time

led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

while True:
print("Hello back to you!")
led.value = True
time.sleep(1)
led.value = False
time.sleep(1)

Keep your serial console window where you can see it. Save your file. You'll see what

the serial console displays when the board reboots. Then you'll see your new change!

The Traceback (most recent call last): is telling you the last thing your board

was doing before you saved your file. This is normal behavior and will happen every

time the board resets. This is really handy for troubleshooting. Let's introduce an error

so you can see how it is used.

Delete the e at the end of True from the line led.value = True so that it says le

d.value = Tru

import board
import digitalio
import time

©Adafruit Industries Page 50 of 215

led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

while True:
print("Hello back to you!")
led.value = Tru
time.sleep(1)
led.value = False
time.sleep(1)

Save your file. You will notice that your red LED will stop blinking, and you may have a

colored status LED blinking at you. This is because the code is no longer correct and

can no longer run properly. You need to fix it!

Usually when you run into errors, it's not because you introduced them on purpose.

You may have 200 lines of code, and have no idea where your error could be hiding.

This is where the serial console can help. Let's take a look!

The Traceback (most recent call last): is telling you that the last thing it was
able to run was line 10 in your code. The next line is your error: NameError: name

'Tru' is not defined . This error might not mean a lot to you, but combined with

knowing the issue is on line 10, it gives you a great place to start!

Go back to your code, and take a look at line 10. Obviously, you know what the

problem is already. But if you didn't, you'd want to look at line 10 and see if you could

figure it out. If you're still unsure, try googling the error to get some help. In this case,

you know what to look for. You spelled True wrong. Fix the typo and save your file.

©Adafruit Industries Page 51 of 215

Nice job fixing the error! Your serial console is streaming and your red LED Is blinking

again.

The serial console will display any output generated by your code. Some sensors,

such as a humidity sensor or a thermistor, receive data and you can use print

statements to display that information. You can also use print statements for

troubleshooting, which is called "print debugging". Essentially, if your code isn't

working, and you want to know where it's failing, you can put print statements in

various places to see where it stops printing.

The serial console has many uses, and is an amazing tool overall for learning and

programming!

The REPL

The other feature of the serial connection is the Read-Evaluate-Print-Loop, or REPL.

The REPL allows you to enter individual lines of code and have them run immediately.

It's really handy if you're running into trouble with a particular program and can't

figure out why. It's interactive so it's great for testing new ideas.

Entering the REPL

To use the REPL, you first need to be connected to the serial console. Once that

connection has been established, you'll want to press CTRL+C.

If there is code running, in this case code measuring distance, it will stop and you'll
see Press any key to enter the REPL. Use CTRL-D to reload. Follow those

instructions, and press any key on your keyboard.

©Adafruit Industries Page 52 of 215

The Traceback (most recent call last): is telling you the last thing your board
was doing before you pressed Ctrl + C and interrupted it. The KeyboardInterrupt

is you pressing CTRL+C. This information can be handy when troubleshooting, but for

now, don't worry about it. Just note that it is expected behavior.

If your code.py file is empty or does not contain a loop, it will show an empty output
and Code done running. . There is no information about what your board was

doing before you interrupted it because there is no code running.

If you have no code.py on your CIRCUITPY drive, you will enter the REPL immediately

after pressing CTRL+C. Again, there is no information about what your board was

doing before you interrupted it because there is no code running.

Regardless, once you press a key you'll see a >>> prompt welcoming you to the

REPL!

If you have trouble getting to the >>> prompt, try pressing Ctrl + C a few more times.

©Adafruit Industries Page 53 of 215

The first thing you get from the REPL is information about your board.

This line tells you the version of CircuitPython you're using and when it was released.

Next, it gives you the type of board you're using and the type of microcontroller the

board uses. Each part of this may be different for your board depending on the

versions you're working with.

This is followed by the CircuitPython prompt.

Interacting with the REPL

From this prompt you can run all sorts of commands and code. The first thing you'll do
is run help() . This will tell you where to start exploring the REPL. To run code in the

REPL, type it in next to the REPL prompt.

Type help() next to the prompt in the REPL.

Then press enter. You should then see a message.

First part of the message is another reference to the version of CircuitPython you're

using. Second, a URL for the CircuitPython related project guides. Then... wait. What's
this? To list built-in modules type `help("modules")`. Remember the

modules you learned about while going through creating code? That's exactly what

this is talking about! This is a perfect place to start. Let's take a look!

Type help("modules") into the REPL next to the prompt, and press enter.

©Adafruit Industries Page 54 of 215

This is a list of all the core modules built into CircuitPython, including board .
Remember, board contains all of the pins on the board that you can use in your

code. From the REPL, you are able to see that list!

Type import board into the REPL and press enter. It'll go to a new prompt. It might
look like nothing happened, but that's not the case! If you recall, the import

statement simply tells the code to expect to do something with that module. In this

case, it's telling the REPL that you plan to do something with that module.

Next, type dir(board) into the REPL and press enter.

This is a list of all of the pins on your board that are available for you to use in your

code. Each board's list will differ slightly depending on the number of pins available.
Do you see LED ? That's the pin you used to blink the red LED!

The REPL can also be used to run code. Be aware that any code you enter into the

REPL isn't saved anywhere. If you're testing something new that you'd like to keep,

make sure you have it saved somewhere on your computer as well!

Every programmer in every programming language starts with a piece of code that

says, "Hello, World." You're going to say hello to something else. Type into the REPL:

print("Hello, CircuitPython!")

©Adafruit Industries Page 55 of 215

Then press enter.

That's all there is to running code in the REPL! Nice job!

You can write single lines of code that run stand-alone. You can also write entire

programs into the REPL to test them. Remember that nothing typed into the REPL is

saved.

There's a lot the REPL can do for you. It's great for testing new ideas if you want to

see if a few new lines of code will work. It's fantastic for troubleshooting code by

entering it one line at a time and finding out where it fails. It lets you see what

modules are available and explore those modules.

Try typing more into the REPL to see what happens!

Everything typed into the REPL is ephemeral. Once you reload the REPL or return

to the serial console, nothing you typed will be retained in any memory space. So

be sure to save any desired code you wrote somewhere else, or you'll lose it

when you leave the current REPL instance!

Returning to the Serial Console

When you're ready to leave the REPL and return to the serial console, simply press CT

RL+D. This will reload your board and reenter the serial console. You will restart the

program you had running before entering the REPL. In the console window, you'll see

any output from the program you had running. And if your program was affecting

anything visual on the board, you'll see that start up again as well.

You can return to the REPL at any time!

©Adafruit Industries Page 56 of 215

CircuitPython Libraries

As CircuitPython development continues and there are new releases, Adafruit

will stop supporting older releases. Visit https://circuitpython.org/downloads to

download the latest version of CircuitPython for your board. You must download

the CircuitPython Library Bundle that matches your version of CircuitPython.

Please update CircuitPython and then visit https://circuitpython.org/libraries to

download the latest Library Bundle.

Each CircuitPython program you run needs to have a lot of information to work. The

reason CircuitPython is so simple to use is that most of that information is stored in

other files and works in the background. These files are called libraries. Some of them

are built into CircuitPython. Others are stored on your CIRCUITPY drive in a folder

called lib. Part of what makes CircuitPython so great is its ability to store code

separately from the firmware itself. Storing code separately from the firmware makes

it easier to update both the code you write and the libraries you depend.

Your board may ship with a lib folder already, it's in the base directory of the drive. If

not, simply create the folder yourself. When you first install CircuitPython, an empty lib

directory will be created for you.

CircuitPython libraries work in the same way as regular Python modules so the Python

docs() are an excellent reference for how it all should work. In Python terms, you can

place our library files in the lib directory because it's part of the Python path by

default.

One downside of this approach of separate libraries is that they are not built in. To

use them, one needs to copy them to the CIRCUITPY drive before they can be used.

Fortunately, there is a library bundle.

©Adafruit Industries Page 57 of 215

The bundle and the library releases on GitHub also feature optimized versions of the

libraries with the .mpy file extension. These files take less space on the drive and

have a smaller memory footprint as they are loaded.

Due to the regular updates and space constraints, Adafruit does not ship boards with

the entire bundle. Therefore, you will need to load the libraries you need when you

begin working with your board. You can find example code in the guides for your

board that depends on external libraries.

Either way, as you start to explore CircuitPython, you'll want to know how to get

libraries on board.

The Adafruit Learn Guide Project Bundle

The quickest and easiest way to get going with a project from the Adafruit Learn

System is by utilising the Project Bundle. Most guides now have a Download Project

Bundle button available at the top of the full code example embed. This button

downloads all the necessary files, including images, etc., to get the guide project up

and running. Simply click, open the resulting zip, copy over the right files, and you're

good to go!

The first step is to find the Download Project Bundle button in the guide you're

working on.

The Download Project Bundle button is only available on full demo code

embedded from GitHub in a Learn guide. Code snippets will NOT have the

button available.

©Adafruit Industries Page 58 of 215

When you copy the contents of the Project Bundle to your CIRCUITPY drive, it

will replace all the existing content! If you don't want to lose anything, ensure you

copy your current code to your computer before you copy over the new Project

Bundle content!

The Download Project Bundle button downloads a zip file. This zip contains a series

of directories, nested within which is the code.py, any applicable assets like images or

audio, and the lib/ folder containing all the necessary libraries. The following zip was

downloaded from the Piano in the Key of Lime guide.

The Piano in the Key of Lime guide was chosen as an example. That guide is

specific to Circuit Playground Express, and cannot be used on all boards. Do not

expect to download that exact bundle and have it work on your non-CPX

microcontroller.

When you open the zip, you'll find some nested directories. Navigate through them

until you find what you need. You'll eventually find a directory for your CircuitPython

version (in this case, 7.x). In the version directory, you'll find the file and directory you

need: code.py and lib/. Once you find the content you need, you can copy it all over

to your CIRCUITPY drive, replacing any files already on the drive with the files from

the freshly downloaded zip.

In some cases, there will be other files such as audio or images in the same

directory as code.py and lib/. Make sure you include all the files when you copy

things over!

©Adafruit Industries Page 59 of 215

Once you copy over all the relevant files, the project should begin running! If you find

that the project is not running as expected, make sure you've copied ALL of the

project files onto your microcontroller board.

That's all there is to using the Project Bundle!

The Adafruit CircuitPython Library Bundle

Adafruit provides CircuitPython libraries for much of the hardware they provide,

including sensors, breakouts and more. To eliminate the need for searching for each

library individually, the libraries are available together in the Adafruit CircuitPython

Library Bundle. The bundle contains all the files needed to use each library.

Downloading the Adafruit CircuitPython Library Bundle

You can download the latest Adafruit CircuitPython Library Bundle release by clicking

the button below. The libraries are being constantly updated and improved, so you'll

always want to download the latest bundle.

Match up the bundle version with the version of CircuitPython you are running. For

example, you would download the 6.x library bundle if you're running any version of

CircuitPython 6, or the 7.x library bundle if you're running any version of CircuitPython

7, etc. If you mix libraries with major CircuitPython versions, you will get incompatible

mpy errors due to changes in library interfaces possible during major version

changes.

Click to visit circuitpython.org for the

latest Adafruit CircuitPython Library

Bundle

Download the bundle version that matches your CircuitPython firmware version. If you

don't know the version, check the version info in boot_out.txt file on the CIRCUITPY

drive, or the initial prompt in the CircuitPython REPL. For example, if you're running

v7.0.0, download the 7.x library bundle.

There's also a py bundle which contains the uncompressed python files, you probably

don't want that unless you are doing advanced work on libraries.

©Adafruit Industries Page 60 of 215

The CircuitPython Community Library Bundle

The CircuitPython Community Library Bundle is made up of libraries written and

provided by members of the CircuitPython community. These libraries are often

written when community members encountered hardware not supported in the

Adafruit Bundle, or to support a personal project. The authors all chose to submit

these libraries to the Community Bundle make them available to the community.

These libraries are maintained by their authors and are not supported by Adafruit. As

you would with any library, if you run into problems, feel free to file an issue on the

GitHub repo for the library. Bear in mind, though, that most of these libraries are

supported by a single person and you should be patient about receiving a response.

Remember, these folks are not paid by Adafruit, and are volunteering their personal

time when possible to provide support.

Downloading the CircuitPython Community Library Bundle

You can download the latest CircuitPython Community Library Bundle release by

clicking the button below. The libraries are being constantly updated and improved,

so you'll always want to download the latest bundle.

Click for the latest CircuitPython

Community Library Bundle release

The link takes you to the latest release of the CircuitPython Community Library

Bundle on GitHub. There are multiple versions of the bundle available. Download the

bundle version that matches your CircuitPython firmware version. If you don't know

the version, check the version info in boot_out.txt file on the CIRCUITPY drive, or the

initial prompt in the CircuitPython REPL. For example, if you're running v7.0.0,

download the 7.x library bundle.

Understanding the Bundle

After downloading the zip, extract its contents. This is usually done by double clicking

on the zip. On Mac OSX, it places the file in the same directory as the zip.

©Adafruit Industries Page 61 of 215

Open the bundle folder. Inside you'll find two information files, and two folders. One

folder is the lib bundle, and the other folder is the examples bundle.

Now open the lib folder. When you open the folder, you'll see a large number of .mpy

files, and folders.

Example Files

All example files from each library are now included in the bundles in an examples

directory (as seen above), as well as an examples-only bundle. These are included for

two main reasons:

Allow for quick testing of devices.

•

Provide an example base of code, that is easily built upon for individualized

•

purposes.

©Adafruit Industries Page 62 of 215

Copying Libraries to Your Board

First open the lib folder on your CIRCUITPY drive. Then, open the lib folder you

extracted from the downloaded zip. Inside you'll find a number of folders and .mpy

files. Find the library you'd like to use, and copy it to the lib folder on CIRCUITPY.

If the library is a directory with multiple .mpy files in it, be sure to copy the entire

folder to CIRCUITPY/lib.

This also applies to example files. Open the examples folder you extracted from the

downloaded zip, and copy the applicable file to your CIRCUITPY drive. Then, rename

it to code.py to run it.

If a library has multiple .mpy files contained in a folder, be sure to copy the entire

folder to CIRCUITPY/lib.

Understanding Which Libraries to Install

You now know how to load libraries on to your CircuitPython-compatible

microcontroller board. You may now be wondering, how do you know which libraries

you need to install? Unfortunately, it's not always straightforward. Fortunately, there is

an obvious place to start, and a relatively simple way to figure out the rest. First up:

the best place to start.

When you look at most CircuitPython examples, you'll see they begin with one or
more import statements. These typically look like the following:

import library_or_module

•

©Adafruit Industries Page 63 of 215

However, import statements can also sometimes look like the following:

from library_or_module import name

•

from library_or_module.subpackage import name

•

from library_or_module import name as local_name

•

They can also have more complicated formats, such as including a try / except

block, etc.

The important thing to know is that an import statement will always include the

name of the module or library that you're importing.

Therefore, the best place to start is by reading through the import statements.

Here is an example import list for you to work with in this section. There is no setup or

other code shown here, as the purpose of this section involves only the import list.

import time
import board
import neopixel
import adafruit_lis3dh
import usb_hid
from adafruit_hid.consumer_control import ConsumerControl
from adafruit_hid.consumer_control_code import ConsumerControlCode

Keep in mind, not all imported items are libraries. Some of them are almost always

built-in CircuitPython modules. How do you know the difference? Time to visit the

REPL.

In the Interacting with the REPL section() on The REPL page() in this guide, the

help("modules") command is discussed. This command provides a list of all of the

built-in modules available in CircuitPython for your board. So, if you connect to the
serial console on your board, and enter the REPL, you can run help("modules") to
see what modules are available for your board. Then, as you read through the impor

t statements, you can, for the purposes of figuring out which libraries to load, ignore

the statement that import modules.

The following is the list of modules built into CircuitPython for the Feather RP2040.

Your list may look similar or be anything down to a significant subset of this list for

smaller boards.

©Adafruit Industries Page 64 of 215

Now that you know what you're looking for, it's time to read through the import
statements. The first two, time and board , are on the modules list above, so they're

built-in.

The next one, neopixel , is not on the module list. That means it's your first library!

So, you would head over to the bundle zip you downloaded, and search for neopixel.

There is a neopixel.mpy file in the bundle zip. Copy it over to the lib folder on your CI
RCUITPY drive. The following one, adafruit_lis3dh , is also not on the module list.

Follow the same process for adafruit_lis3dh, where you'll find adafruit_lis3dh.mpy,

and copy that over.

The fifth one is usb_hid , and it is in the modules list, so it is built in. Often all of the

built-in modules come first in the import list, but sometimes they don't! Don't assume

that everything after the first library is also a library, and verify each import with the

modules list to be sure. Otherwise, you'll search the bundle and come up empty!

The final two imports are not as clear. Remember, when import statements are
formatted like this, the first thing after the from is the library name. In this case, the
library name is adafruit_hid . A search of the bundle will find an adafruit_hid folder.

When a library is a folder, you must copy the entire folder and its contentsas it is in

the bundle to the lib folder on your CIRCUITPY drive. In this case, you would copy the

entire adafruit_hid folder to your CIRCUITPY/lib folder.

Notice that there are two imports that begin with adafruit_hid . Sometimes you will

need to import more than one thing from the same library. Regardless of how many

times you import the same library, you only need to load the library by copying over

the adafruit_hid folder once.

That is how you can use your example code to figure out what libraries to load on

your CircuitPython-compatible board!

©Adafruit Industries Page 65 of 215

There are cases, however, where libraries require other libraries internally. The

internally required library is called a dependency. In the event of library

dependencies, the easiest way to figure out what other libraries are required is to
connect to the serial console and follow along with the ImportError printed there.
The following is a very simple example of an ImportError , but the concept is the

same for any missing library.

Example: ImportError Due to Missing Library

If you choose to load libraries as you need them, or you're starting fresh with an

existing example, you may end up with code that tries to use a library you haven't yet

loaded. This section will demonstrate what happens when you try to utilise a library

that you don't have loaded on your board, and cover the steps required to resolve the

issue.

This demonstration will only return an error if you do not have the required library

loaded into the lib folder on your CIRCUITPY drive.

Let's use a modified version of the Blink example.

import board
import time
import simpleio

led = simpleio.DigitalOut(board.LED)

while True:
led.value = True
time.sleep(0.5)
led.value = False
time.sleep(0.5)

Save this file. Nothing happens to your board. Let's check the serial console to see

what's going on.

©Adafruit Industries Page 66 of 215

You have an ImportError . It says there is no module named 'simpleio' . That's

the one you just included in your code!

Click the link above to download the correct bundle. Extract the lib folder from the

downloaded bundle file. Scroll down to find simpleio.mpy. This is the library file you're

looking for! Follow the steps above to load an individual library file.

The LED starts blinking again! Let's check the serial console.

No errors! Excellent. You've successfully resolved an ImportError !

If you run into this error in the future, follow along with the steps above and choose

the library that matches the one you're missing.

Library Install on Non-Express Boards

If you have an M0 non-Express board such as Trinket M0, Gemma M0, QT Py M0, or

one of the M0 Trinkeys, you'll want to follow the same steps in the example above to
install libraries as you need them. Remember, you don't need to wait for an ImportEr

ror if you know what library you added to your code. Open the library bundle you

downloaded, find the library you need, and drag it to the lib folder on your CIRCUITPY

drive.

You can still end up running out of space on your M0 non-Express board even if you

only load libraries as you need them. There are a number of steps you can use to try

to resolve this issue. You'll find suggestions on the Troubleshooting page().

Updating CircuitPython Libraries and Examples

Libraries and examples are updated from time to time, and it's important to update the

files you have on your CIRCUITPY drive.

©Adafruit Industries Page 67 of 215

To update a single library or example, follow the same steps above. When you drag

the library file to your lib folder, it will ask if you want to replace it. Say yes. That's it!

A new library bundle is released every time there's an update to a library. Updates

include things like bug fixes and new features. It's important to check in every so

often to see if the libraries you're using have been updated.

CircUp CLI Tool

There is a command line interface (CLI) utility called CircUp() that can be used to

easily install and update libraries on your device. Follow the directions on the install

page within the CircUp learn guide(). Once you've got it installed you run the

command circup update in a terminal to interactively update all libraries on the

connected CircuitPython device. See the usage page in the CircUp guide() for a full

list of functionality

CircuitPython Documentation

You've learned about the CircuitPython built-in modules and external libraries. You

know that you can find the modules in CircuitPython, and the libraries in the Library

Bundles. There are guides available that explain the basics of many of the modules

and libraries. However, there's sometimes more capabilities than are necessarily

showcased in the guides, and often more to learn about a module or library. So,

where can you find more detailed information? That's when you want to look at the

API documentation.

The entire CircuitPython project comes with extensive documentation available on

Read the Docs. This includes both the CircuitPython core() and the Adafruit

CircuitPython libraries().

CircuitPython Core Documentation

The CircuitPython core documentation() covers many of the details you might want to

know about the CircuitPython core and related topics. It includes API and usage info,

a design guide and information about porting CircuitPython to new boards,

MicroPython info with relation to CircuitPython, and general information about the

project.

©Adafruit Industries Page 68 of 215

The main page covers the basics including where to download CircuitPython, how to

contribute, differences from MicroPython, information about the project structure, and

a full table of contents for the rest of the documentation.

The list along the left side leads to more information about specific topics.

The first section is API and Usage. This is where you can find information about how
to use individual built-in core modules, such as time and digitalio , details about

the supported ports, suggestions for troubleshooting, and basic info and links to the li

brary bundles. The Core Modules section also includes the Support Matrix, which is a

table of which core modules are available on which boards.

The second section is Design and Porting Reference. It includes a design guide, archit

ecture information, details onporting, and adding module support to other ports.

The third section is MicroPython Specific. It includes information on MicroPython and

related libraries, and a glossary of terms.

The fourth and final section is About the Project. It includes further information

including details on building, testing, and debugging CircuitPython, along with various

other useful links including the Adafruit Community Code of Conduct.

Whether you're a seasoned pro or new to electronics and programming, you'll find a

wealth of information to help you along your CircuitPython journey in the

documentation!

©Adafruit Industries Page 69 of 215

CircuitPython Library Documentation

The Adafruit CircuitPython libraries are documented in a very similar fashion. Each

library has its own page on Read the Docs. There is a comprehensive list available her

e(). Otherwise, to view the documentation for a specific library, you can visit the

GitHub repository for the library, and find the link in the README.

For the purposes of this page, the LED Animation library() documentation will be

featured. There are two links to the documentation in each library GitHub repo. The

first one is the docs badge near the top of the README.

The second place is the Documentation section of the README. Scroll down to find it,

and click on Read the Docs to get to the documentation.

Now that you know how to find it, it's time to take a look at what to expect.

Not all library documentation will look exactly the same, but this will give you

some idea of what to expect from library docs.

The Introduction page is generated from the README, so it includes all the same info,

such as PyPI installation instructions, a quick demo, and some build details. It also

includes a full table of contents for the rest of the documentation (which is not part of

the GitHub README). The page should look something like the following.

The left side contains links to the rest of the documentation, divided into three

separate sections: Examples, API Reference, and Other Links.

©Adafruit Industries Page 70 of 215

Examples

The Examples section() is a list of library examples. This list contains anywhere from a

small selection to the full list of the examples available for the library.

This section will always contain at least one example - the simple test example.

The simple test example is usually a basic example designed to show your setup is

working. It may require other libraries to run. Keep in mind, it's simple - it won't

showcase a comprehensive use of all the library features.

The LED Animation simple test demonstrates the Blink animation.

In some cases, you'll find a longer list, that may include examples that explore other

features in the library. The LED Animation documentation includes a series of

examples, all of which are available in the library. These examples include

demonstrations of both basic and more complex features. Simply click on the example

that interests you to view the associated code.

©Adafruit Industries Page 71 of 215

When there are multiple links in the Examples section, all of the example content

is, in actuality, on the same page. Each link after the first is an anchor link to the

specified section of the page. Therefore, you can also view all the available

examples by scrolling down the page.

You can view the rest of the examples by clicking through the list or scrolling down

the page. These examples are fully working code. Which is to say, while they may rely

on other libraries as well as the library for which you are viewing the documentation,

they should not require modification to otherwise work.

API Reference

The API Reference section() includes a list of the library functions and classes. The

API (Application Programming Interface) of a library is the set of functions and classes

the library provides. Essentially, the API defines how your program interfaces with the

functions and classes that you call in your code to use the library.

There is always at least one list item included. Libraries for which the code is included

in a single Python (.py) file, will only have one item. Libraries for which the code is

multiple Python files in a directory (called subpackages) will have multiple items in this

list. The LED Animation library has a series of subpackages, and therefore, multiple

items in this list.

Click on the first item in the list to begin viewing the API Reference section.

As with the Examples section, all of the API Reference content is on a single

page, and the links under API Reference are anchor links to the specified section

of the page.

©Adafruit Industries Page 72 of 215

When you click on an item in the API Reference section, you'll find details about the

classes and functions in the library. In the case of only one item in this section, all the

available functionality of the library will be contained within that first and only

subsection. However, in the case of a library that has subpackages, each item will

contain the features of the particular subpackage indicated by the link. The

documentation will cover all of the available functions of the library, including more

complex ones that may not interest you.

The first list item is the animation subpackage. If you scroll down, you'll begin to see

the available features of animation. They are listed alphabetically. Each of these

things can be called in your code. It includes the name and a description of the

specific function you would call, and if any parameters are necessary, lists those with

a description as well.

You can view the other subpackages by clicking the link on the left or scrolling down

the page. You may be interested in something a little more practical. Here is an

example. To use the LED Animation library Comet animation, you would run the

following example.

# SPDX-FileCopyrightText: 2021 Kattni Rembor for Adafruit Industries
# SPDX-License-Identifier: MIT

"""
This example animates a jade comet that bounces from end to end of the strip.

For QT Py Haxpress and a NeoPixel strip. Update pixel_pin and pixel_num to match
your wiring if
using a different board or form of NeoPixels.

This example will run on SAMD21 (M0) Express boards (such as Circuit Playground
Express or QT Py
Haxpress), but not on SAMD21 non-Express boards (such as QT Py or Trinket).
"""
import board
import neopixel

from adafruit_led_animation.animation.comet import Comet
from adafruit_led_animation.color import JADE

©Adafruit Industries Page 73 of 215

# Update to match the pin connected to your NeoPixels
pixel_pin = board.A3
# Update to match the number of NeoPixels you have connected
pixel_num = 30

pixels = neopixel.NeoPixel(pixel_pin, pixel_num, brightness=0.5, auto_write=False)

comet = Comet(pixels, speed=0.02, color=JADE, tail_length=10, bounce=True)

while True:
comet.animate()

Note the line where you create the comet object. There are a number of items inside

the parentheses. In this case, you're provided with a fully working example. But what

if you want to change how the comet works? The code alone does not explain what

the options mean.

So, in the API Reference documentation list, click the

adafruit_led_animation.animation.comet link and scroll down a bit until you

see the following.

Look familiar? It is! This is the documentation for setting up the comet object. It

explains what each argument provided in the comet setup in the code meant, as well
as the other available features. For example, the code includes speed=0.02 . The

documentation clarifies that this is the "Animation speed in seconds". The code
doesn't include ring . The documentation indicates this is an available setting that

enables "Ring mode".

This type of information is available for any function you would set up in your code. If

you need clarification on something, wonder whether there's more options available,

or are simply interested in the details involved in the code you're writing, check out

the documentation for the CircuitPython libraries!

©Adafruit Industries Page 74 of 215

Other Links

This section is the same for every library. It includes a list of links to external sites,

which you can visit for more information about the CircuitPython Project and Adafruit.

That covers the CircuitPython library documentation! When you are ready to go

beyond the basic library features covered in a guide, or you're interested in

understanding those features better, the library documentation on Read the Docs has

you covered!

Recommended Editors

The CircuitPython code on your board detects when the files are changed or written

and will automatically re-start your code. This makes coding very fast because you

save, and it re-runs.

However, you must wait until the file is done being saved before unplugging or

resetting your board! On Windows using some editors this can sometimes take up to

90 seconds, on Linux it can take 30 seconds to complete because the text editor

does not save the file completely. Mac OS does not seem to have this delay, which is

nice!

This is really important to be aware of. If you unplug or reset the board before your

computer finishes writing the file to your board, you can corrupt the drive. If this

happens, you may lose the code you've written, so it's important to backup your code

to your computer regularly.

To avoid the likelihood of filesystem corruption, use an editor that writes out the file

completely when you save it. Check out the list of recommended editors below.

Recommended editors

mu() is an editor that safely writes all changes (it's also our recommended

•

editor!)

emacs() is also an editor that will fulIy write files on save()

•

Sublime Text()safelywrites all changes

•

Visual Studio Code() appears to safely write all changes

•

gedit on Linux appears to safely write all changes

•

IDLE(), in Python 3.8.1 or later, was fixed() to write all changes immediately

•

Thonny() fully writes files on save

•

©Adafruit Industries Page 75 of 215

Recommended only with particular settings or add-ons

vim()/visafely writes all changes. But set upvimto not write swapfiles() (.swp

•

files: temporary records of your edits) to CIRCUITPY. Run vim with vim -n ,set
the no swapfile option, or set the directory option to write swapfiles

elsewhere. Otherwise the swapfile writestrigger restarts of your program.

ThePyCharm IDE()is safe if "Safe Write" is turned on in Settings->System

•

Settings->Synchronization (true by default).

If you are usingAtom(), install thefsync-on-save package() or the language-

•

circuitpython package() so that it will always write out all changes to files on CIR

CUITPY.

SlickEdit()works only if youadd a macro to flush the disk().

•

The editors listed below are specifically NOT recommended!

Editors that are NOT recommended

notepad (the default Windows editor) and Notepad++ can be slow to write, so

•

the editors above are recommended! If you are using notepad, be sure to eject

the drive.

IDLE in Python 3.8.0 or earlier does not force out changes immediately.

•

nano (on Linux) does not force out changes.

•

geany (on Linux) does not force out changes.

•

Anything else - Other editors have not been tested so please use a

•

recommended one!

Advanced Serial Console on Windows

Windows 7 and 8.1

If you're using Windows 7 (or 8 or 8.1), you'll need to install drivers. See the Windows 7

and 8.1 Drivers page() for details. You will not need to install drivers on Mac, Linux or

Windows 10.

You are strongly encouraged to upgrade to Windows 10 if you are still using Windows

7 or Windows 8 or 8.1. Windows 7 has reached end-of-life and no longer receives

security updates. A free upgrade to Windows 10 is still available().

©Adafruit Industries Page 76 of 215

What's the COM?

First, you'll want to find out which serial port your board is using. When you plug your

board in to USB on your computer, it connects to a serial port. The port is like a door

through which your board can communicate with your computer using USB.

You'll use Windows Device Manager to determine which port the board is using. The

easiest way to determine which port the board is using is to first check without the

board plugged in. Open Device Manager. Click on Ports (COM & LPT). You should find

something already in that list with (COM#) after it where # is a number.

Now plug in your board. The Device Manager list will refresh and a new item will

appear under Ports (COM & LPT). You'll find a different (COM#) after this item in the

list.

©Adafruit Industries Page 77 of 215

Sometimes the item will refer to the name of the board. Other times it may be called

something like USB Serial Device, as seen in the image above. Either way, there is a

new (COM#) following the name. This is the port your board is using.

Install Putty

If you're using Windows, you'll need to download a terminal program. You're going to

use PuTTY.

The first thing to do is download the latest version of PuTTY(). You'll want to

download the Windows installer file. It is most likely that you'll need the 64-bit version.

Download the file and install the program on your machine. If you run into issues, you

can try downloading the 32-bit version instead. However, the 64-bit version will work

on most PCs.

Now you need to open PuTTY.

Under Connection type: choose the button next to Serial.

•

In the box under Serial line, enter the serial port you found that your board is

•

using.

In the box under Speed, enter 115200. This called the baud rate, which is the

•

speed in bits per second that data is sent over the serial connection. For boards

with built in USB it doesn't matter so much but for ESP8266 and other board

©Adafruit Industries Page 78 of 215

with a separate chip, the speed required by the board is 115200 bits per second.

So you might as well just use 115200!

If you want to save those settings for later, use the options under Load, save or delete

a stored session. Enter a name in the box under Saved Sessions, and click the Save

button on the right.

Once your settings are entered, you're ready to connect to the serial console. Click

"Open" at the bottom of the window. A new window will open.

©Adafruit Industries Page 79 of 215

If no code is running, the window will either be blank or will look like the window

above. Now you're ready to see the results of your code.

Great job! You've connected to the serial console!

Advanced Serial Console on Mac

Connecting to the serial console on Mac does not require installing any drivers or
extra software. You'll use a terminal program to find your board, and screen to
connect to it. Terminal and screen both come installed by default.

What's the Port?

First you'll want to find out which serial port your board is using. When you plug your

board in to USB on your computer, it connects to a serial port. The port is like a door

through which your board can communicate with your computer using USB.

The easiest way to determine which port the board is using is to first check without

the board plugged in. Open Terminal and type the following:

ls /dev/tty.*

Each serial connection shows up in the /dev/ directory. It has a name that starts with

tty. . The command ls shows you a list of items in a directory. You can use * as a

wildcard, to search for files that start with the same letters but end in something
different. In this case, you're asking to see all of the listings in /dev/ that start with t

ty. and end in anything. This will show us the current serial connections.

©Adafruit Industries Page 80 of 215

Now, plug your board. In Terminal, type:

ls /dev/tty.*

This will show you the current serial connections, which will now include your board.

A new listing has appeared called /dev/tty.usbmodem141441 . The tty.usbmodem1

41441 part of this listing is the name the example board is using. Yours will be called

something similar.

Using Linux, a new listing has appeared called /dev/ttyACM0 . The ttyACM0 part of

this listing is the name the example board is using. Yours will be called something

similar.

Connect with screen

Now that you know the name your board is using, you're ready connect to the serial
console. You're going to use a command called screen . The screen command is

included with MacOS. To connect to the serial console, use Terminal. Type the
following command, replacing board_name with the name you found your board is

using:

screen /dev/tty.board_name 115200

The first part of this establishes using the screen command. The second part tells

screen the name of the board you're trying to use. The third part tells screen what

baud rate to use for the serial connection. The baud rate is the speed in bits per

second that data is sent over the serial connection. In this case, the speed required

by the board is 115200 bits per second.

©Adafruit Industries Page 81 of 215

Press enter to run the command. It will open in the same window. If no code is

running, the window will be blank. Otherwise, you'll see the output of your code.

Great job! You've connected to the serial console!

Advanced Serial Console on Linux

Connecting to the serial console on Linux does not require installing any drivers, but
you may need to install screen using your package manager. You'll use a terminal
program to find your board, and screen to connect to it. There are a variety of

terminal programs such as gnome-terminal (called Terminal) or Konsole on KDE.

The tio program works as well to connect to your board, and has the benefit of

automatically reconnecting. You would need to install it using your package manager.

What's the Port?

First you'll want to find out which serial port your board is using. When you plug your

board in to USB on your computer, it connects to a serial port. The port is like a door

through which your board can communicate with your computer using USB.

The easiest way to determine which port the board is using is to first check without

the board plugged in. Open your terminal program and type the following:

ls /dev/ttyACM*

Each serial connection shows up in the /dev/ directory. It has a name that starts with tt
yACM. The command ls shows you a list of items in a directory. You can use * as a

wildcard, to search for files that start with the same letters but end in something

©Adafruit Industries Page 82 of 215

different. In this case, You're asking to see all of the listings in /dev/ that start with ttyA

CM and end in anything. This will show us the current serial connections.

In the example below, the error is indicating that are no current serial connections

starting with ttyACM.

Now plug in your board. In your terminal program, type:

ls /dev/ttyACM*

This will show you the current serial connections, which will now include your board.

A new listing has appeared called /dev/ttyACM0. The ttyACM0 part of this listing is

the name the example board is using. Yours will be called something similar.

Connect with screen

Now that you know the name your board is using, you're ready connect to the serial
console. You'll use a command called screen . You may need to install it using the

package manager.

©Adafruit Industries Page 83 of 215

To connect to the serial console, use your terminal program. Type the following
command, replacing board_name with the name you found your board is using:

screen /dev/tty.board_name 115200

The first part of this establishes using the screen command. The second part tells

screen the name of the board you're trying to use. The third part tells screen what

baud rate to use for the serial connection. The baud rate is the speed in bits per

second that data is sent over the serial connection. In this case, the speed required

by the board is 115200 bits per second.

Press enter to run the command. It will open in the same window. If no code is

running, the window will be blank. Otherwise, you'll see the output of your code.

Great job! You've connected to the serial console!

Permissions on Linux

If you try to run screen and it doesn't work, then you may be running into an issue

with permissions. Linux keeps track of users and groups and what they are allowed to

do and not do, like access the hardware associated with the serial connection for
running screen . So if you see something like this:

©Adafruit Industries Page 84 of 215

then you may need to grant yourself access. There are generally two ways you can do
this. The first is to just run screen using the sudo command, which temporarily

gives you elevated privileges.

Once you enter your password, you should be in:

The second way is to add yourself to the group associated with the hardware. To
figure out what that group is, use the command ls -l as shown below. The group

name is circled in red.

Then use the command adduser to add yourself to that group. You need elevated
privileges to do this, so you'll need to use sudo . In the example below, the group is a

dm and the user is ackbar.

After you add yourself to the group, you'll need to logout and log back in, or in some

cases, reboot your machine. After you log in again, verify that you have been added
to the group using the command groups . If you are still not in the group, reboot and

check again.

©Adafruit Industries Page 85 of 215

And now you should be able to run screen without using sudo .

And you're in:

The examples above use screen , but you can also use other programs, such as put

ty or picocom , if you prefer.

Troubleshooting

From time to time, you will run into issues when working with CircuitPython. Here are

a few things you may encounter and how to resolve them.

As CircuitPython development continues and there are new releases, Adafruit

will stop supporting older releases. Visit https://circuitpython.org/downloads to

download the latest version of CircuitPython for your board. You must download

the CircuitPython Library Bundle that matches your version of CircuitPython.

Please update CircuitPython and then visit https://circuitpython.org/libraries to

download the latest Library Bundle.

©Adafruit Industries Page 86 of 215

Always Run the Latest Version of CircuitPython and Libraries

As CircuitPython development continues and there are new releases, Adafruit will

stop supporting older releases. You need to update to the latest CircuitPython.().

You need to download the CircuitPython Library Bundle that matches your version of

CircuitPython. Please update CircuitPython and then download the latest bundle().

As new versions of CircuitPython are released, Adafruit will stop providing the

previous bundles as automatically created downloads on the Adafruit CircuitPython

Library Bundle repo. If you must continue to use an earlier version, you can still
download the appropriate version of mpy-cross from the particular release of

CircuitPython on the CircuitPython repo and create your own compatible .mpy library

files. However, it is best to update to the latest for both CircuitPython and the library

bundle.

I have to continue using CircuitPython 5.x or earlier. Where can I find compatible libraries?

Adafruit is no longer building or supporting the CircuitPython 5.x or earlier library

bundles. You are highly encourged to update CircuitPython to the latest version() and

use the current version of the libraries(). However, if for some reason you cannot

update, links to the previous bundles are available in the FAQ().

Bootloader (boardnameBOOT) Drive Not Present

You may have a different board.

Only Adafruit Express boards and the SAMD21 non-Express boards ship with the UF2

bootloader ()installed. The Feather M0 Basic, Feather M0 Adalogger, and similar

boards use a regular Arduino-compatible bootloader, which does not show a boardna

meBOOT drive.

©Adafruit Industries Page 87 of 215

MakeCode

If you are running a MakeCode() program on Circuit Playground Express, press the

reset button just onceto get the CPLAYBOOT drive to show up. Pressing it twice will

not work.

MacOS

DriveDx and its accompanything SAT SMART Driver can interfere with seeing the

BOOT drive. See this forum post() for how to fix the problem.

Windows 10

Did you install the Adafruit Windows Drivers package by mistake, or did you upgrade

to Windows 10 with the driver package installed? You don't need to install this

package on Windows 10 for most Adafruit boards. The old version (v1.5) can interfere

with recognizing your device. Go to Settings -> Apps and uninstall all the "Adafruit"

driver programs.

Windows 7 or 8.1

To use a CircuitPython-compatible board with Windows 7 or 8.1, you must install a

driver. Installation instructions are available here().

It is recommended() that you upgrade to Windows 10 if possible; an upgrade is

probably still free for you. Check here().

The Windows Drivers installer was last updated in November 2020 (v2.5.0.0) .

Windows 7 drivers for CircuitPython boards released since then, including

RP2040 boards, are not yet available. The boards work fine on Windows 10. A

new release of the drivers is in process.

You should now be done! Test by unplugging and replugging the board. You should

see the CIRCUITPY drive, and when you double-click the reset button (single click on

Circuit Playground Express running MakeCode), you should see the appropriateboar

dnameBOOT drive.

Let us know in the Adafruit support forums() or on the Adafruit Discord() if this does

not work for you!

©Adafruit Industries Page 88 of 215

Windows Explorer Locks Up When Accessing boardnameBOOT Drive

On Windows, several third-party programs that can cause issues. The symptom is that

you try to access the boardnameBOOTdrive, and Windows or Windows Explorer

seems to lock up. These programs are known to cause trouble:

AIDA64: to fix, stop the program. This problem has been reported to AIDA64.

•

They acquired hardware to test, and released a beta version that fixes the

problem. This may have been incorporated into the latest release. Please let us

know in the forums if you test this.

Hard Disk Sentinel

•

Kaspersky anti-virus: To fix, you may need to disable Kaspersky completely.

•

Disabling some aspects of Kaspersky does not always solve the problem. This

problem has been reported to Kaspersky.

ESET NOD32 anti-virus: There have been problems with at least version

•

9.0.386.0, solved by uninstallation.

Copying UF2 to boardnameBOOT Drive Hangs at 0% Copied

On Windows, a Western DIgital (WD) utility that comes with their external USB drives

can interfere with copying UF2 files to the boardnameBOOT drive. Uninstall that utility

to fix the problem.

CIRCUITPY Drive Does Not Appear or Disappears Quickly

Kaspersky anti-virus can block the appearance of the CIRCUITPY drive. There has not

yet been settings change discovered that prevents this. Complete uninstallation of

Kaspersky fixes the problem.

Norton anti-virus can interfere with CIRCUITPY. A user has reported this problem on

Windows 7. The user turned off both Smart Firewall and Auto Protect, and CIRCUITPY

then appeared.

©Adafruit Industries Page 89 of 215

Sophos Endpoint security software can cause CIRCUITPY to disappear() and the

BOOT drive to reappear. It is not clear what causes this behavior.

Device Errors or Problems on Windows

Windows can become confused about USB device installations. This is particularly

true of Windows 7 and 8.1. It is recommended() that you upgrade to Windows 10 if

possible; an upgrade is probably still free for you: see this link().

If not, try cleaning up your USB devices. Use Uwe Sieber's Device Cleanup Tool()(on

that page, scroll down to "Device Cleanup Tool"). Download and unzip the tool.

Unplug all the boards and other USB devices you want to clean up. Run the tool as

Administrator. You will see a listing like this, probably with many more devices. It is

listing all the USB devices that are not currently attached.

Select all the devices you want to remove, and then press Delete. It is usually safe

just to select everything. Any device that is removed will get a fresh install when you

plug it in. Using the Device Cleanup Tool also discards all the COM port assignments

for the unplugged boards. If you have used many Arduino and CircuitPython boards,

you have probably seen higher and higher COM port numbers used, seemingly

without end. This will fix that problem.

Serial Console in Mu Not Displaying Anything

There are times when the serial console will accurately not display anything, such as,

when no code is currently running, or when code with no serial output is already

©Adafruit Industries Page 90 of 215

running before you open the console. However, if you find yourself in a situation

where you feel it should be displaying something like an error, consider the following.

Depending on the size of your screen or Mu window, when you open the serial

console, the serial console panel may be very small. This can be a problem. A basic

CircuitPython error takes 10 lines to display!

Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
Traceback (most recent call last):
File "code.py", line 7
SyntaxError: invalid syntax

Press any key to enter the REPL. Use CTRL-D to reload.

More complex errors take even more lines!

Therefore, if your serial console panel is five lines tall or less, you may only see blank
lines or blank lines followed by Press any key to enter the REPL. Use CTRL-D

to reload. . If this is the case, you need to either mouse over the top of the panel to

utilise the option to resize the serial panel, or use the scrollbar on the right side to

scroll up and find your message.

This applies to any kind of serial output whether it be error messages or print

statements. So before you start trying to debug your problem on the hardware side,

be sure to check that you haven't simply missed the serial messages due to serial

output panel height.

code.py Restarts Constantly

CircuitPython will restart code.py if you or your computer writes to something on the

CIRCUITPY drive. This feature is called auto-reload, and lets you test a change to your

program immediately.

Some utility programs, such as backup, anti-virus, or disk-checking apps, will write to

the CIRCUITPY as part of their operation. Sometimes they do this very frequently,

causing constant restarts.

©Adafruit Industries Page 91 of 215

Acronis True Image and related Acronis programs on Windows are known to cause

this problem. It is possible to prevent this by disabling the "()Acronis Managed

Machine Service Mini"().

If you cannot stop whatever is causing the writes, you can disable auto-reload by

putting this code in boot.py or code.py:

import supervisor

supervisor.disable_autoreload()

CircuitPython RGB Status Light

Nearly all CircuitPython-capable boards have a single NeoPixel or DotStar RGB LED

on the board that indicates the status of CircuitPython. A few boards designed before

CircuitPython existed, such as the Feather M0 Basic, do not.

Circuit Playground Express and Circuit Playground Bluefruit have multiple RGB LEDs,

but do NOT have a status LED. The LEDs are all green when in the bootloader. In

versions before 7.0.0, they do NOT indicate any status while running CircuitPython.

CircuitPython 7.0.0 and Later

The status LED blinks were changed in CircuitPython 7.0.0 in order to save battery

power and simplify the blinks. These blink patterns will occur on single color LEDs

when the board does not have any RGB LEDs. Speed and blink count also vary for

this reason.

On start up, the LED will blink YELLOW multiple times for 1 second. Pressing the

RESET button (or on Espressif, the BOOT button) during this time will restart the board

and then enter safe mode. On Bluetooth capable boards, after the yellow blinks, there

will be a set of faster blue blinks. Pressing reset during the BLUE blinks will clear

Bluetooth information and start the device in discoverable mode, so it can be used

with a BLE code editor.

Once started, CircuitPython will blink a pattern every 5 seconds when no user code is

running to indicate why the code stopped:

1 GREEN blink: Code finished without error.•

©Adafruit Industries Page 92 of 215

2 RED blinks:Code ended due to an exception. Check the serial console for

•

details.

3 YELLOW blinks:CircuitPython is in safe mode. No user code was run. Check

•

the serial console for safe mode reason.

When in the REPL, CircuitPython will set the status LED to WHITE. You can change the

LED color from the REPL. The status indicator will not persist on non-NeoPixel or

DotStar LEDs.

CircuitPython 6.3.0 and earlier

Here's what the colors and blinking mean:

steady GREEN: code.py (or code.txt, main.py, or main.txt) is running

•

pulsing GREEN: code.py (etc.) has finished or does not exist

•

steady YELLOW at start up: (4.0.0-alpha.5 and newer) CircuitPython is waiting for

•

a reset to indicate that it should start in safe mode

pulsing YELLOW: Circuit Python is in safe mode: it crashed and restarted

•

steady WHITE: REPL is running

•

steady BLUE: boot.py is running

•

Colors with multiple flashes following indicate a Pythonexception and then indicate

the line number of the error. The color of the first flash indicates the type of error:

GREEN:IndentationError

•

©Adafruit Industries Page 93 of 215

CYAN:SyntaxError

•

WHITE: NameError

•

ORANGE: OSError

•

PURPLE: ValueError

•

YELLOW: other error

•

These are followed by flashes indicating the line number, including place value. WHIT

E flashes are thousands' place, BLUE are hundreds' place, YELLOW are tens' place,

and CYAN are one's place. So for example, an error on line 32 would flash YELLOW

three times and then CYAN two times. Zeroes are indicated by an extra-long dark gap.

Serial console showing ValueError:

Incompatible .mpy file

This error occurs when importing a module that is stored as a .mpy binary file that

was generated by a different version of CircuitPython than the one its being loaded

into. In particular, the mpy binary format changed between CircuitPython versions 6.x

and 7.x, 2.x and 3.x, and 1.x and 2.x.

So, for instance, if you upgraded to CircuitPython 7.x from 6.x you’ll need to download
a newer version of the library that triggered the error on import . All libraries are

available in the Adafruit bundle().

©Adafruit Industries Page 94 of 215

CIRCUITPY Drive Issues

You may find that you can no longer save files to your CIRCUITPY drive. You may find

that your CIRCUITPY stops showing up in your file explorer, or shows up as NO_NAM

E. These are indicators that your filesystem has issues. When the CIRCUITPY disk is

not safely ejected before being reset by the button or being disconnected from USB,

it may corrupt the flash drive. It can happen on Windows, Mac or Linux, though it is

more common on Windows.

Be aware, if you have used Arduino to program your board, CircuitPython is no longer

able to provide the USB services. You will need to reload CircuitPython to resolve this

situation.

The easiest first step is to reload CircuitPython. Double-tap reset on the board so you

get a boardnameBOOT drive rather than a CIRCUITPY drive, and copy the latest

version of CircuitPython (.uf2) back to the board. This may restore CIRCUITPY

functionality.

If reloading CircuitPython does not resolve your issue, the next step is to try putting

the board into safe mode.

Safe Mode

Whether you've run into a situation where you can no longer edit your code.py on

your CIRCUITPY drive, your board has gotten into a state where CIRCUITPY is read-

only, or you have turned off the CIRCUITPY drive altogether, safe mode can help.

Safe mode in CircuitPython does not run any user code on startup, and disables auto-

reload. This means a few things. First, safe mode bypasses any code in boot.py

(where you can set CIRCUITPY read-only or turn it off completely). Second, it does not

run the code in code.py. And finally, it does not automatically soft-reload when data is

written to the CIRCUITPY drive.

Therefore, whatever you may have done to put your board in a non-interactive state,

safe mode gives you the opportunity to correct it without losing all of the data on the

CIRCUITPY drive.

©Adafruit Industries Page 95 of 215

Entering Safe Mode in CircuitPython 7.x and Later

To enter safe mode when using CircuitPython 7.x, plug in your board or hit reset

(highlighted in red above). Immediately after the board starts up or resets, it waits

1000ms. On some boards, the onboard status LED will blink yellow during that time. If

you press reset during that 1000ms, the board will start up in safe mode. It can be

difficult to react to the yellow LED, so you may want to think of it simply as a "slow"

double click of the reset button. (Remember, a fast double click of reset enters the

bootloader.)

Entering Safe Mode in CircuitPython 6.x

To enter safe mode when using CircuitPython 6.x, plug in your board or hit reset

(highlighted in red above). Immediately after the board starts up or resets, it waits

700ms. On some boards, the onboard status LED (highlighted in green above) will

turn solid yellow during this time. If you press reset during that 700ms, the board will

start up in safe mode. It can be difficult to react to the yellow LED, so you may want to

think of it simply as a slow double click of the reset button. (Remember, a fast double

click of reset enters the bootloader.)

In Safe Mode

Once you've entered safe mode successfully in CircuitPython 6.x, the LED will pulse

yellow.

If you successfully enter safe mode on CircuitPython 7.x, the LED will intermittently

blink yellow three times.

If you connect to the serial console, you'll find the following message.

Auto-reload is off.
Running in safe mode! Not running saved code.

CircuitPython is in safe mode because you pressed the reset button during boot.
Press again to exit safe mode.

Press any key to enter the REPL. Use CTRL-D to reload.

You can now edit the contents of the CIRCUITPY drive. Remember, your code will not

run until you press the reset button, or unplug and plug in your board, to get out of

safe mode.

©Adafruit Industries Page 96 of 215

At this point, you'll want to remove any user code incode.py and, if present, the boot.

py file from CIRCUITPY. Once removed, tap the reset button, or unplug and plug in

your board, to restart CircuitPython. This will restart the board and may resolve your

drive issues. If resolved, you can begin coding again as usual.

If safe mode does not resolve your issue, the board must be completely erased and

CircuitPython must be reloaded onto the board.

You WILL lose everything on the board when you complete the following steps. If

possible, make a copy of your code before continuing.

To erase CIRCUITPY: storage.erase_filesystem()

CircuitPython includes a built-in function to erase and reformat the filesystem. If you

have a version of CircuitPython older than 2.3.0 on your board, you can update to the

newest version() to do this.

Connect to the CircuitPython REPL()using Mu or a terminal program.

1.

Type the following into the REPL:

2.

>>> import storage
>>> storage.erase_filesystem()

CIRCUITPY will be erased and reformatted, and your board will restart. That's it!

Erase CIRCUITPY Without Access to the REPL

If you can't access the REPL, or you're running a version of CircuitPython previous to

2.3.0 and you don't want to upgrade, there are options available for some specific

boards.

The options listed below are considered to be the "old way" of erasing your board.

The method shown above using the REPL is highly recommended as the best method

for erasing your board.

If at all possible, it is recommended to use the REPL to erase your CIRCUITPY

drive. The REPL method is explained above.

©Adafruit Industries Page 97 of 215

For the specific boards listed below:

If the board you are trying to erase is listed below, follow the steps to use the file to

erase your board.

 1. Download the correct erase file:

Circuit Playground Express

Feather M0 Express

Feather M4 Express

Metro M0 Express

Metro M4 Express QSPI Eraser

Trellis M4 Express (QSPI)

Grand Central M4 Express (QSPI)

PyPortal M4 Express (QSPI)

Circuit Playground Bluefruit (QSPI)

Monster M4SK (QSPI)

PyBadge/PyGamer QSPI Eraser.UF2

CLUE_Flash_Erase.UF2

Matrix_Portal_M4_(QSPI).UF2

 2. Double-click the reset button on the board to bring up the boardnameBOOT

drive.

 3. Drag the erase .uf2 file to theboardnameBOOT drive.

©Adafruit Industries Page 98 of 215

 4. The status LED will turn yellow or blue, indicating the erase has started.

 5. After approximately 15 seconds, the status LED will light up green. On the

NeoTrellis M4 this is the first NeoPixel on the grid

 6. Double-click the reset button on the board to bring up theboardnameBOOTd

rive.

 7. Drag the appropriate latest release of CircuitPython() .uf2 file to theboardnam

eBOOTdrive.

It should reboot automatically and you should see CIRCUITPY in your file explorer

again.

If the LED flashes red during step 5, it means the erase has failed. Repeat the steps

starting with 2.

If you haven't already downloaded the latest release of CircuitPython for your board,

check out the installation page(). You'll also need to load your code and reinstall your

libraries!

For SAMD21 non-Express boards that have a UF2 bootloader:

Any SAMD21-based microcontroller that does not have external flash available is

considered a SAMD21 non-Express board. Non-Express boards that have a UF2

bootloader include Trinket M0, GEMMA M0, QT Py M0, and the SAMD21-based

Trinkey boards.

If you are trying to erase a SAMD21 non-Express board, follow these steps to erase

your board.

 1. Download the erase file:

SAMD21 non-Express Boards

 2. Double-click the reset button on the board to bring up the boardnameBOOT

drive.

 3. Drag the erase .uf2 file to the boardnameBOOT drive.

 4. The boot LED will start flashing again, and the boardnameBOOT drive will

reappear.

 5. Drag the appropriate latest release CircuitPython() .uf2 file to the

boardnameBOOT drive.

©Adafruit Industries Page 99 of 215

It should reboot automatically and you should see CIRCUITPY in your file explorer

again.

If you haven't already downloaded the latest release of CircuitPython for your board,

check out the installation page() YYou'll also need to load your code and reinstall

your libraries!

For SAMD21 non-Express boards that do not have a UF2 bootloader:

Any SAMD21-based microcontroller that does not have external flash available is

considered a SAMD21 non-Express board. Non-Express boards that do not have a

UF2 bootloader include the Feather M0 Basic Proto, Feather Adalogger, or the

Arduino Zero.

If you are trying to erase a non-Express board that does not have a UF2 bootloader, f

ollow these directions toreload CircuitPython using bossac (), which will erase and

re-create CIRCUITPY.

Running Out of File Space on SAMD21 Non­Express Boards

Any SAMD21-based microcontroller that does not have external flash available is

considered a SAMD21 non-Express board. This includes boards like the Trinket M0,

GEMMA M0, QT Py M0, and the SAMD21-based Trinkey boards.

The file system on the board is very tiny. (Smaller than an ancient floppy disk.) So, its

likely you'll run out of space but don't panic! There are a number of ways to free up

space.

©Adafruit Industries Page 100 of 215