Adafruit Feather M4 Express User Manual

Adafruit Feather M4 Express

Created by lady ada

Last updated on 2021-09-07 12:57:52 PM EDT

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Guide Contents

Guide Contents Overview Update the UF2 Bootloader

Updating Your Bootloader

Pinouts Power Pins Logic pins

I2S Pins: Parallel Capture Peripheral

QSPI Flash and NeoPixel Other Pins! Debugging Interface Assembly Header Options! Soldering in Plain Headers

Prepare the header strip: Add the breakout board: And Solder!

Soldering on Female Header

Tape In Place Flip & Tack Solder And Solder!

Power Management Battery + USB Power Power supplies Measuring Battery ENable pin Alternative Power Options Arduino IDE Setup

https://adafruit.github.io/arduino-board-index/package_adafruit_index.json

Using with Arduino IDE Install SAMD Support Install Adafruit SAMD Install Drivers (Windows 7 & 8 Only) Blink Successful Upload Compilation Issues Manually bootloading Ubuntu & Linux Issue Fix Adapting Sketches to M0 & M4 Analog References Pin Outputs & Pullups Serial vs SerialUSB AnalogWrite / PWM on Feather/Metro M0 analogWrite() PWM range

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analogWrite() DAC on A0 Missing header files Bootloader Launching Aligned Memory Access Floating Point Conversion How Much RAM Available? Storing data in FLASH Pretty-Printing out registers M4 Performance Options

CPU Speed (overclocking) Optimize Cache Max SPI and Max QSPI

Enabling the Buck Converter on some M4 Boards What is CircuitPython? CircuitPython is based on Python

Why would I use CircuitPython?

CircuitPython on Feather M4 Express

Set up CircuitPython Quick Start! Further Information

Installing Mu Editor Download and Install Mu Using Mu Creating and Editing Code

Creating Code Editing Code

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

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

2. Eject or Sync the Drive After Writing Oh No I Did Something Wrong and Now The CIRCUITPY Drive Doesn't Show Up!!!

Back to Editing Code... 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?

More Changes Naming Your Program File Connecting to the Serial Console Are you using Mu?

Setting Permissions on Linux

Using Something Else? Interacting with the Serial Console The REPL Returning to the serial console CircuitPython Libraries

Installing the CircuitPython Library Bundle Example Files

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Copying Libraries to Your Board

Example: ImportError Due to Missing Library Library Install on Non-Express Boards Updating CircuitPython Libraries/Examples

Frequently Asked Questions

I have to continue using an older version of CircuitPython; where can I find compatible libraries? Is ESP8266 or ESP32 supported in CircuitPython? Why not? How do I connect to the Internet with CircuitPython? Is there asyncio support in CircuitPython? My RGB NeoPixel/DotStar LED is blinking funny colors - what does it mean? What is a MemoryError? What do I do when I encounter a MemoryError? Can the order of my import statements affect memory? How can I create my own .mpy files? How do I check how much memory I have free? Does CircuitPython support interrupts? Does Feather M0 support WINC1500? Can AVRs such as ATmega328 or ATmega2560 run CircuitPython? Commonly Used Acronyms

Welcome to the Community!

Adafruit Discord Adafruit Forums Adafruit Github ReadTheDocs

Advanced Serial Console on Windows Windows 7 Driver What's the COM? Install Putty Advanced Serial Console on Mac and Linux What's the Port? Connect with screen Permissions on Linux Uninstalling CircuitPython

Backup Your Code

Moving Circuit Playground Express to MakeCode Moving to Arduino Troubleshooting Always Run the Latest Version of CircuitPython and Libraries I have to continue using CircuitPython 5.x, 4.x, 3.x or 2.x, where can I find compatible libraries? CPLAYBOOT, TRINKETBOOT, FEATHERBOOT, or GEMMABOOT Drive Not Present

You may have a different board. MakeCode MacOS Windows 10 Windows 7 or 8.1

Windows Explorer Locks Up When Accessing boardnameBOOT Drive Copying UF2 to boardnameBOOT Drive Hangs at 0% Copied CIRCUITPY Drive Does Not Appear Windows 7 and 8.1 Problems

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Serial Console in Mu Not Displaying Anything CircuitPython RGB Status Light ValueError: Incompatible .mpy file. CIRCUITPY Drive Issues

Easiest Way: Use storage.erase_filesystem() Old Way: For the Circuit Playground Express, Feather M0 Express, and Metro M0 Express: Old Way: For Non-Express Boards with a UF2 bootloader (Gemma M0, Trinket M0): Old Way: For non-Express Boards without a UF2 bootloader (Feather M0 Basic Proto, Feather Adalogger, Arduino Zero):

Running Out of File Space on Non-Express Boards

Delete something! Use tabs MacOS loves to add extra files. Prevent & Remove MacOS Hidden Files Copy Files on MacOS Without Creating Hidden Files Other MacOS Space-Saving Tips

Device locked up or boot looping CircuitPython Essentials CircuitPython Pins and Modules CircuitPython Pins

import board I2C, SPI, and UART What Are All the Available Names? Microcontroller Pin Names

CircuitPython Built-In Modules CircuitPython Built-Ins Thing That Are Built In and Work

Flow Control Math Tuples, Lists, Arrays, and Dictionaries Classes, Objects and Functions Lambdas Random Numbers

CircuitPython Digital In & Out

Find the pins! Read the Docs

CircuitPython Analog In

Creating the analog input get_voltage Helper Main Loop Changing It Up Wire it up

Reading Analog Pin Values CircuitPython Analog Out

Creating an analog output Setting the analog output Main Loop Find the pin

CircuitPython PWM

PWM with Fixed Frequency Create a PWM Output Main Loop

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PWM Output with Variable Frequency Wire it up Where's My PWM?

CircuitPython Servo

Servo Wiring Standard Servo Code Continuous Servo Code

CircuitPython Internal RGB LED

Create the LED Brightness Main Loop Making Rainbows (Because Who Doesn't Love 'Em!) Circuit Playground Express Rainbow

CircuitPython NeoPixel

Wiring It Up The Code Create the LED NeoPixel Helpers Main Loop NeoPixel RGBW Read the Docs

CircuitPython DotStar

Wire It Up The Code Create the LED DotStar Helpers Main Loop Is it SPI? Read the Docs

CircuitPython UART Serial

The Code Wire It Up Where's my UART? Trinket M0: Create UART before I2C

CircuitPython I2C

Wire It Up Find Your Sensor I2C Sensor Data Where's my I2C?

CircuitPython HID Keyboard and Mouse

CircuitPython Keyboard Emulator Create the Objects and Variables The Main Loop

CircuitPython Mouse Emulator

Create the Objects and Variables CircuitPython HID Mouse Helpers Main Loop

CircuitPython Storage

Logging the Temperature

CircuitPython CPU Temp CircuitPython Expectations Always Run the Latest Version of CircuitPython and Libraries I have to continue using CircuitPython 3.x or 2.x, where can I find compatible libraries?

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Switching Between CircuitPython and Arduino The Difference Between Express And Non-Express Boards Non-Express Boards: Gemma, Trinket, and QT Py

Small Disk Space No Audio or NVM

Differences Between CircuitPython and MicroPython Differences Between CircuitPython and Python

Python Libraries Integers in CircuitPython Floating Point Numbers and Digits of Precision for Floats in CircuitPython Differences between MicroPython and Python

UF2 Bootloader Details Entering Bootloader Mode Using the Mass Storage Bootloader Using the BOSSA Bootloader

Windows 7 Drivers Verifying Serial Port in Device Manager Running bossac on the command line

Using bossac Versions 1.7.0, 1.8 Using bossac Versions 1.9 or Later

Updating the bootloader Getting Rid of Windows Pop-ups Making your own UF2 Installing the bootloader on a fresh/bricked board Downloads Datasheets Schematic & Fab Print

Pinout Diagram

Overview

It's what you've been waiting for, the Feather M4 Express featuring ATSAMD51. This Feather is fast like a swift, smart like an owl, strong like a ox-bird (it's half ox, half bird, OK?) This feather is powered by our new favorite chip, the ATSAMD51J19A - with its 120MHz Cortex M4 with floating point support and 512KB Flash and 192KB RAM. Your code will zig and zag and zoom, and with a bunch of extra peripherals for support, this will for sure be your favorite new chipset.

And best of all, it's a Feather - so you know it will work with all our FeatherWings! What a great way to quickly get up and running.

The most exciting part of the Feather M4 is that while you can use it with the Arduino IDE - and it's bonkers fast when you do, we are shipping it with CircuitPython on board. When you plug it in, it will show up as a very small disk drive with main.py on it. Edit main.py with your favorite text editor to build your project using Python, the most popular programming language. No installs, IDE or compiler needed, so you can use it on any computer, even ChromeBooks or computers you can't install software on. When you're done, unplug the Feather and your code will go with you.

You can also use MakeCode (https://adafru.it/C9N)'s block-based GUI coding on this board.

Here are some of the updates you can look forward to when using Feather M4:

Measures 2.0" x 0.9" x 0.28" (51mm x 23mm x 8mm) without headers soldered in Light as a (large?) feather - 5 grams ATSAMD51 32-bit Cortex M4 core running at 120 MHz, 32-bit, 3.3V logic and power Hardware DSP and floating point support 512 KB flash, 192 KB RAM 2 MB SPI FLASH chip for storing files and CircuitPython code storage. No EEPROM

32.768 KHz crystal for clock generation & RTC

3.3V regulator with 500mA peak current output USB native support, comes with USB bootloader and serial port debugging Built in crypto engines with AES (256 bit), true RNG, Pubkey controller Tons of GPIO! 21 x GPIO pins with following capabilities:

Dual 1 MSPS 12 bit true analog DAC (A0 and A1) - can be used to play 12-bit stereo audio clips Dual 1 MSPS 12 bit ADC (6 analog pins some on ADC1 and some on ADC2) 6 x hardware SERCOM - Native hardware SPI, I2C and Serial all available 16 x PWM outputs - for servos, LEDs, etc I2S input and output 8-bit Parallel capture controller (for camera/video in)

Built in 100mA lipoly charger with charging status indicator LED Pin #13 red LED for general purpose blinking Power/enable pin 4 mounting holes Reset button

The Feather M4 Express uses the extra space left over to add a Mini NeoPixel, 2 MB SPI Flash storage and a little prototyping space. You can use the SPI Flash storage like a very tiny hard drive. When used in CircuitPython, the 2 MB flash acts as storage for all your scripts, libraries and files. When used in Arduino, you can read/write files to it, like a little datalogger or SD card, and then with our helper program, access the files over USB.

Easy reprogramming: the Feather M4 comes pre-loaded with the UF2 bootloader (https://adafru.it/vQd), which looks like a USB storage key. Simply drag firmware on to program, no special tools or drivers needed! It can be used to load up CircuitPython or Arduino IDE (it is bossa-compatible)

Comes fully assembled and tested, with the UF2 USB bootloader. We also toss in some headers so you can solder it in and plug into a solderless breadboard.

Update the UF2 Bootloader

Your SAMD51 M4 board bootloader may need to be updated to fix an intermittent bug that can erase parts of internal flash.

Updating Your Bootloader

To see if you need to update your bootloader, get the UF2 boot drive to appear as a mounted drive on your computer, in a file browser window. If you're running MakeCode, click the reset button once. If you're running CircuitPython or an Arduino program, double-click the reset button.

When you see the ...BOOT drive (FEATHERBOOT, METROM4BOOT, ITSYM4BOOT, PORTALBOOT, etc.) , click the drive in the file browser window and then double-click the INFO_UF2.TXT file to see what's inside.

The example screenshots below are for a PyGamer. What you see for your board will be largely the same except for the board name and the BOOT drive name.

The bootloader version is listed in INFO_UF2.TXT. In this example, the version is v3.6.0.

Update the Bootloader on your SAMD51 M4 board to prevent a somewhat rare problem of parts of internal flash being overwritten on power-up.



If the bootloader version you see is older than

v3.9.0

, you need to update. For instance, the bootloader

above needs to be upgraded.

Download the latest version of the bootloader updater from the circuitpython.org Downloads page for your board.

https://adafru.it/Em8

The bootloader updater will be named update-bootloader-

name_of_your_board

-v3.9.0.uf2 or some

later version. Drag that file from your Downloads folder onto the BOOT drive:

https://adafru.it/Em8

After you drag the updater onto the boot drive, the red LED on the board will flicker and then blink slowly about five times. A few seconds later, the BOOT will appear in the Finder. After that, you can click on the BOOT drive and double-click INFO_UF2.TXT again to confirm you've updated the bootloader.

Pinouts

The Feather M4 is chock-full of microcontroller goodness. There's also a lot of pins and ports. We'll take you a tour of them now!

Power Pins

GND - this is the common ground for all power and logic BAT - this is the positive voltage to/from the JST jack for the optional Lipoly battery USB - this is the positive voltage to/from the micro USB jack if 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 3V - this is the output from the 3.3V regulator, it can supply 500mA peak

Logic pins

This is the general purpose I/O pin set for the microcontroller.

All logic is 3.3V Nearly all pins can do PWM output All pins can be interrupt inputs

#0 / RX - GPIO #0, also receive (input) pin for Serial1 (hardware UART). Also PWM out #1 / TX - GPIO #1, also transmit (output) pin for Serial1. PWM out SDA - the I2C (Wire) data pin. There's no pull up on this pin by default so when using with I2C, you may need a 2.2K-10K pullup. Also GPIO #21. Also PWM out SCL - the I2C (Wire) clock pin. There's no pull up on this pin by default so when using with I2C, you

may need a 2.2K-10K pullup. Also GPIO #22. Also PWM out #4 - GPIO #4, PWM out #5 - GPIO #5, PWM out #6 - GPIO #6, PWM out #9 - GPIO #9, PWM out #10 - GPIO #10, PWM out #11 - GPIO #11, PWM out #12 - GPIO #12, PWM out #13 - GPIO #13, PWM out and is connected to the red LED next to the USB jack SCK/MOSI/MISO - These are the hardware SPI pins, you can use them as everyday GPIO #25/#24/#23 pins (but recommend keeping them free as they are best used for hardware SPI

connections for high speed.)

Analog Pins:

A0 - This pin is analog

input

A0 but is also an analog

output

due to having a DAC (digital-to-analog converter). You can set the raw voltage to anything from 0 to 3.3V, unlike PWM outputs this is a true analog output A1 - This pin is analog

input

A1 but is also an analog

output

due to having a DAC (digital-to-analog converter). This is the second DAC, and is 'independent' of A0. You can set the raw voltage to anything from 0 to 3.3V, unlike PWM outputs this is a true analog output. Also can do PWM. A2 thru A5 - These are each analog input as well as digital I/O pins. These pins can also do PWM.

I2S Pins:

#1/Tx - I2S bit_clock pin. #10 - I2S word_select pin. #11 - I2S data pin.

These pins are available in CircuitPython under the board module. Names that start with # are prefixed with D and other names are as is. So #0 / RX above is available as board.D0 and board.RX for example.

Parallel Capture Peripheral

There's a 'camera' input peripheral you can use with some camera chips to capture video with 8-bit data width. We thought this was neat so we made sure all those pins were available. Here are the PCC pins (left) and the Feather M4 pins it's mapped to. Unlike other peripherals, you cannot mux these signals to other pins!

DEN1: SDA DEN2: SCL CLK: D6 D0: D11 D1: D13

D2: D10 D3: D12 D4: MISO D5: D5 D6: MOSI D7: SCK

QSPI Flash and NeoPixel

As part of the 'Express' series of boards, the Feather M4 Express is designed for use with CircuitPython. To make that easy, we have added two extra parts to this Feather M4: a mini NeoPixel (RGB LED) and a 2 MB QSPI (Quad SPI) Flash chip

The NeoPixel is connected to pin #8 in Arduino, so just use our NeoPixel library (https://adafru.it/dhw) and set it up as a single-LED strand on pin 8. In CircuitPython, the NeoPixel is board.NEOPIXEL and the library

for it is here (https://adafru.it/wby) and in the bundle (https://adafru.it/uap). The NeoPixel is powered by the

3.3V power supply but that hasn't shown to make a big difference in brightness or color. The NeoPixel is also used by the bootloader to let you know if the device has enumerated correctly (green) or USB failure (red). In CircuitPython, the LED is used to indicate the runtime status.

The QSPI Flash 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 reality is at least 10x faster because you can

clock the QSPI peripheral much faster than a plain SPI peripheral

However, the QSPI port is

not

also on an SERCOM. So, you have to either use the QSPI peripheral or bitbang SPI if you want to talk to the chip. We have an Arduino library here which provides QSPI

interfacing for Arduino (https://adafru.it/BeX). In CircuitPython, the QSPI flash is used natively by the

interpretter and is read-only to user code, instead the Flash just shows up as the writeable disk drive!

Other Pins!

RST - this is the Reset pin, tie to ground to manually reset the ATSAMD51, as well as launch the bootloader manually ARef - the analog reference pin. Normally the reference voltage is the same as the chip logic voltage (3.3V) but if you need an alternative analog reference, connect it to this pin and select the external AREF in your firmware. Can't go higher than 3.3V!

Debugging Interface

If you'd like to do more advanced development, trace-debugging, or not use the bootloader, we have the SWD interface exposed. You'll have to solder to the two SWD/SWCLK pads on the bottom:

On the Feather M4, at least for now, AREF is tied to 3.3V due to a silicon v0 bug that does not allow the DACs to work unless AREF is connected to 3.3V. You cut the bottom jumper if you need a different AREF voltage but note that this may change DAC range!



Assembly

We ship Feathers fully tested but without headers attached - this gives you the most flexibility on choosing how to use and configure your Feather

Header Options!

Before you go gung-ho on soldering, there's a few options to consider!

The first option is soldering in plain male headers, this lets you plug in the Feather into a solderless breadboard

Another option is to go with socket female headers. This won't let you plug the Feather into a breadboard but it will let you attach featherwings very easily

We also have 'slim' versions of the female headers, that are a little shorter and give a more compact shape

Finally, there's the "Stacking Header" option. This one is sort of the best-of-both-worlds. You get the ability to plug into a solderless breadboard

and

plug a featherwing on

top. But its a little bulky

Soldering in Plain Headers

Prepare the header strip:

Cut the strip to length if necessary. It will be easier to solder if you insert it into a breadboard - long pins down

Add the breakout board:

Place the breakout board over the pins so that the short pins poke through the breakout pads

And Solder!

Be sure to solder all pins for reliable electrical contact.

(For tips on soldering, be sure to check out our Guide to

Excellent Soldering

(https://adafru.it/aTk)

).

Solder the other strip as well.

You're done! Check your solder joints visually and continue onto the next steps

Soldering on Female Header

Tape In Place

For sockets you'll want to tape them in place so when you flip over the board they don't fall out

Flip & Tack Solder

After flipping over, solder one or two points on each strip, to 'tack' the header in place

And Solder!

Be sure to solder all pins for reliable electrical contact.

(For tips on soldering, be sure to check out our Guide to

Excellent Soldering

(https://adafru.it/aTk)

).

You're done! Check your solder joints visually and continue onto the next steps

Power Management

Battery + USB Power

We wanted to make the Feather 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 MicroUSB cable (just plug into the jack) and the Feather will regulate the 5V USB down to 3.3V. You can also connect a 4.2/3.7V Lithium Polymer (Lipo/Lipoly) or Lithium Ion (LiIon) battery to the JST jack. This will let the Feather run on a rechargable 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) at 100mA. This happens 'hotswap' 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



The above shows the Micro USB jack (left), Lipoly JST jack (top left), as well as the changeover diode (just to the right of the JST jack) and the Lipoly charging circuitry (to the right of the JST jack). There's also a CHG LED, which will light up while the battery is charging. This LED might also flicker if the battery is not connected.

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. It's fine for, say, powering an ESP8266 WiFi chip or XBee radio though, since the current draw is 'spikey' & sporadic.

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

To make this easy we stuck a double-100K resistor divider on the BAT pin, and connected it to A6 which is not exposed on the feather breakout

In Arduino, you can read this pin's voltage, then double it, to get the battery voltage.

// Arduino Example Code snippet

#define VBATPIN A6

float measuredvbat = analogRead(VBATPIN); measuredvbat *= 2; // we divided by 2, so multiply back measuredvbat *= 3.3; // Multiply by 3.3V, our reference voltage measuredvbat /= 1024; // convert to voltage Serial.print("VBat: " ); Serial.println(measuredvbat);

For CircuitPython, we've written a get_voltage() helper function to do the math for you. All you have to do is call the function, provide the pin and print the results.

import board from analogio import AnalogIn

vbat_voltage = AnalogIn(board.VOLTAGE_MONITOR)

def get_voltage(pin): return (pin.value * 3.3) / 65536 * 2

battery_voltage = get_voltage(vbat_voltage) print("VBat voltage: {:.2f}".format(battery_voltage))

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

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 (https://adafru.it/duP) 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! (https://adafru.it/e2q) If you have a higher voltage power supply, use a 5V buck converter (https://adafru.it/DHs) and wire it to a USB cable's 5V and GND input (https://adafru.it/DHu)

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. 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.

Arduino IDE Setup

The first thing you will need to do is to download the latest release of the Arduino IDE. You will need to be using version 1.8 or higher for this guide

https://adafru.it/f1P

After you have downloaded and installed the latest version of Arduino IDE , you will need to start the IDE and navigate to the Preferences menu. You can access it from the File menu in

Windows

or

Linux

, or

the Arduino menu on

OS X

.

A dialog will pop up just like the one shown below.

https://adafru.it/f1P

We will be adding a URL to the new Additional Boards Manager URLs option. The list of URLs is comma separated, and

you will only have to add each URL once.

New Adafruit boards and updates to existing boards will automatically be picked up by the Board Manager each time it is opened. The URLs point to index files that the Board Manager uses to build the list of available & installed boards.

To find the most up to date list of URLs you can add, you can visit the list of third party board URLs on the

Arduino IDE wiki (https://adafru.it/f7U). We will only need to add one URL to the IDE in this example, but

you can add multiple URLS by separating them with commas

. Copy and paste the link below into

the Additional Boards Manager URLs option in the Arduino IDE preferences.

https://adafruit.github.io/arduino-board-index/package_adafruit_index.json

Here's a short description of each of the Adafruit supplied packages that will be available in the Board Manager when you add the URL:

Adafruit AVR Boards - Includes support for Flora, Gemma, Feather 32u4, ItsyBitsy 32u4, Trinket, & Trinket Pro. Adafruit SAMD Boards - Includes support for Feather M0 and M4, Metro M0 and M4, ItsyBitsy M0 and M4, Circuit Playground Express, Gemma M0 and Trinket M0 Arduino Leonardo & Micro MIDI-USB - This adds MIDI over USB support for the Flora, Feather 32u4, Micro and Leonardo using the arcore project (https://adafru.it/eSI).

If you have multiple boards you want to support, say ESP8266 and Adafruit, have both URLs in the text box separated by a comma (,)

Once done click OK to save the new preference settings. Next we will look at installing boards with the Board Manager.

Now continue to the next step to actually install the board support package!

Using with Arduino IDE

The Feather/Metro/Gemma/QTPy/Trinket M0 and M4 use an ATSAMD21 or ATSAMD51 chip, and you can pretty easily get it working with the Arduino IDE. Most libraries (including the popular ones like NeoPixels and display) will work with the M0 and M4, especially devices & sensors that use I2C or SPI.

Now that you have added the appropriate URLs to the Arduino IDE preferences in the previous page, you can open the Boards Manager by navigating to the Tools->Board menu.

Once the Board Manager opens, click on the category drop down menu on the top left hand side of the window and select All. You will then be able to select and install the boards supplied by the URLs added to the preferences.

Install SAMD Support

First up, install the latest Arduino SAMD Boards (version 1.6.11 or later)

You can type Arduino SAMD in the top search bar, then when you see the entry, click Install

Remember you need SETUP the Arduino IDE to support our board packages - see the previous page on how to add adafruit's URL to the preferences

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Install Adafruit SAMD

Next you can install the Adafruit SAMD package to add the board file definitions

Make sure you have Type All selected to the left of the

Filter your search...

box

You can type Adafruit SAMD in the top search bar, then when you see the entry, click Install

Even though in theory you don't need to - I recommend rebooting the IDE

Quit and reopen the Arduino IDE to ensure that all of the boards are properly installed. You should now be able to select and upload to the new boards listed in the Tools->Board menu.

Select the matching board, the current options are:

Feather M0 (for use with any Feather M0 other than the Express)

Feather M0 Express Metro M0 Express Circuit Playground Express Gemma M0 Trinket M0 QT Py M0 ItsyBitsy M0 Hallowing M0 Crickit M0 (this is for direct programming of the Crickit, which is probably not what you want! For

advanced hacking only)

Metro M4 Express Grand Central M4 Express ItsyBitsy M4 Express Feather M4 Express Trellis M4 Express PyPortal M4 PyPortal M4 Titano PyBadge M4 Express Metro M4 Airlift Lite PyGamer M4 Express MONSTER M4SK Hallowing M4 MatrixPortal M4 BLM Badge

Install Drivers (Windows 7 & 8 Only)

When you plug in the board, you'll need to possibly install a driver

Click below to download our Driver Installer

https://adafru.it/EC0

Download and run the installer

Run the installer! Since we bundle the SiLabs and FTDI drivers as well, you'll need to click through the license

Select which drivers you want to install, the defaults will set you up with just about every Adafruit board!

Click Install to do the installin'

Blink

Now you can upload your first blink sketch!

Plug in the M0 or M4 board, and wait for it to be recognized by the OS (just takes a few seconds). It will create a serial/COM port, you can now select it from the drop-down, it'll even be 'indicated' as Trinket/Gemma/Metro/Feather/ItsyBitsy/Trellis!

Please note, the QT Py and Trellis M4 Express are two of our very few boards that does not have an onboard pin 13 LED so you can follow this section to practice uploading but you wont see an LED blink!

Now load up the Blink example

// the setup function runs once when you press reset or power the board void setup() { // initialize digital pin 13 as an output. pinMode(13, OUTPUT); }

// the loop function runs over and over again forever void loop() { digitalWrite(13, HIGH); // turn the LED on (HIGH is the voltage level) delay(1000); // wait for a second digitalWrite(13, LOW); // turn the LED off by making the voltage LOW delay(1000); // wait for a second }

And click upload! That's it, you will be able to see the LED blink rate change as you adapt the delay() calls.

Successful Upload

If you have a successful upload, you'll get a bunch of red text that tells you that the device was found and it was programmed, verified & reset

After uploading, you may see a message saying "Disk Not Ejected Properly" about the ...BOOT drive. You can ignore that message: it's an artifact of how the bootloader and uploading work.

If you are having issues, make sure you selected the matching Board in the menu that matches the hardware you have in your hand.



Compilation Issues

If you get an alert that looks like

Cannot run program "{runtime.tools.arm-none-eabi-gcc.path}\bin\arm-non-eabi-g++"

Make sure you have installed the Arduino SAMD boards package, you need

both

Arduino & Adafruit

SAMD board packages

Manually bootloading

If you ever get in a 'weird' spot with the bootloader, or you have uploaded code that crashes and doesn't auto-reboot into the bootloader, click the RST button twice (like a double-click)to get back into the bootloader.

The red LED will pulse and/or RGB LED will be green, so you know that its in bootloader mode.

Once it is in bootloader mode, you can select the newly created COM/Serial port and re-try uploading.

You may need to go back and reselect the 'normal' USB serial port next time you want to use the normal upload.

Ubuntu & Linux Issue Fix

Follow the steps for installing Adafruit's udev rules on this page. (https://adafru.it/iOE)

Adapting Sketches to M0 & M4

The ATSAMD21 and 51 are very nice little chips, but fairly new as Arduino-compatible cores go. Most sketches & libraries will work but here’s a collection of things we noticed.

The notes below cover a range of Adafruit M0 and M4 boards, but not every rule will apply to every board (e.g. Trinket and Gemma M0 do not have ARef, so you can skip the Analog References note!).

Analog References

If you'd like to use the ARef pin for a non-3.3V analog reference, the code to use is

analogReference(AR_EXTERNAL) (it's AR_EXTERNAL not EXTERNAL)

Pin Outputs & Pullups

The old-style way of turning on a pin as an input with a pullup is to use

pinMode(pin, INPUT) digitalWrite(pin, HIGH)

This is because the pullup-selection register on 8-bit AVR chips is the same as the output-selection register.

For M0 & M4 boards, you can't do this anymore! Instead, use:

pinMode(pin, INPUT_PULLUP)

Code written this way still has the benefit of being

backwards compatible with AVR.

You don’t need

separate versions for the different board types.

Serial vs SerialUSB

99.9% of your existing Arduino sketches use Serial.print to debug and give output. For the Official Arduino SAMD/M0 core, this goes to the Serial5 port, which isn't exposed on the Feather. The USB port for the Official Arduino M0 core is called

SerialUSB

instead.

In the Adafruit M0/M4 Core, we fixed it so that Serial goes to USB so it will automatically work just fine .

However, on the off chance you are using the official Arduino SAMD core and

not

the Adafruit version (which really, we recommend you use our version because it’s been tuned to our boards), and you want your Serial prints and reads to use the USB port, use

SerialUSB

instead of

Serial

in your sketch.

If you have existing sketches and code and you want them to work with the M0 without a huge findreplace, put

#if defined(ARDUINO_SAMD_ZERO) && defined(SERIAL_PORT_USBVIRTUAL) // Required for Serial on Zero based boards #define Serial SERIAL_PORT_USBVIRTUAL #endif

right above the first function definition in your code. For example:

AnalogWrite / PWM on Feather/Metro M0

After looking through the SAMD21 datasheet, we've found that some of the options listed in the multiplexer table don't exist on the specific chip used in the Feather M0.

For all SAMD21 chips, there are two peripherals that can generate PWM signals: The Timer/Counter (TC) and Timer/Counter for Control Applications (TCC). Each SAMD21 has multiple copies of each, called 'instances'.

Each TC instance has one count register, one control register, and two output channels. Either channel can be enabled and disabled, and either channel can be inverted. The pins connected to a TC instance can output identical versions of the same PWM waveform, or complementary waveforms.

Each TCC instance has a single count register, but multiple compare registers and output channels. There are options for different kinds of waveform, interleaved switching, programmable dead time, and so on.

The biggest members of the SAMD21 family have five TC instances with two 'waveform output' (WO) channels, and three TCC instances with eight WO channels:

TC[0-4],WO[0-1] TCC[0-2],WO[0-7]

And those are the ones shown in the datasheet's multiplexer tables.

The SAMD21G used in the Feather M0 only has three TC instances with two output channels, and three

TCC instances with eight output channels:

TC[3-5],WO[0-1] TCC[0-2],WO[0-7]

Tracing the signals to the pins broken out on the Feather M0, the following pins can't do PWM at all:

Analog pin A5

The following pins can be configured for PWM without any signal conflicts as long as the SPI, I2C, and UART pins keep their protocol functions:

Digital pins 5, 6, 9, 10, 11, 12, and 13 Analog pins A3 and A4

If only the SPI pins keep their protocol functions, you can also do PWM on the following pins:

TX and SDA (Digital pins 1 and 20)

analogWrite() PWM range

On AVR, if you set a pin's PWM with analogWrite(pin, 255) it will turn the pin fully HIGH. On the ARM cortex, it will set it to be 255/256 so there will be very slim but still-existing pulses-to-0V. If you need the pin to be

fully on, add test code that checks if you are trying to analogWrite(pin, 255) and, instead, does a

digitalWrite(pin, HIGH)

analogWrite() DAC on A0

If you are trying to use analogWrite() to control the DAC output on A0, make sure you do not have a line that sets the pin to output.

Remove

: pinMode(A0, OUTPUT) .

Missing header files

There might be code that uses libraries that are not supported by the M0 core. For example if you have a line with

#include <util/delay.h>

you'll get an error that says

fatal error: util/delay.h: No such file or directory #include <util/delay.h>

^ compilation terminated. Error compiling.

In which case you can simply locate where the line is (the error will give you the file name and line number) and 'wrap it' with #ifdef's so it looks like:

#if !defined(ARDUINO_ARCH_SAM) && !defined(ARDUINO_ARCH_SAMD) && !defined(ESP8266) && !defined(ARDUINO_ARCH_STM32F2) #include <util/delay.h> #endif

The above will also make sure that header file isn't included for other architectures

If the #include is in the arduino sketch itself, you can try just removing the line.

Bootloader Launching

For most other AVRs, clicking reset while plugged into USB will launch the bootloader manually, the bootloader will time out after a few seconds. For the M0/M4, you'll need to

double click

the button. You will see a pulsing red LED to let you know you're in bootloader mode. Once in that mode, it wont time out! Click reset again if you want to go back to launching code.

Aligned Memory Access

This is a little less likely to happen to you but it happened to me! If you're used to 8-bit platforms, you can do this nice thing where you can typecast variables around. e.g.

uint8_t mybuffer[4]; float f = (float)mybuffer;

You can't be guaranteed that this will work on a 32-bit platform because mybuffer might not be aligned to a 2 or 4-byte boundary. The ARM Cortex-M0 can only directly access data on 16-bit boundaries (every 2 or 4 bytes). Trying to access an odd-boundary byte (on a 1 or 3 byte location) will cause a Hard Fault and stop the MCU. Thankfully, there's an easy work around ... just use memcpy!

uint8_t mybuffer[4]; float f; memcpy(&f, mybuffer, 4)

Floating Point Conversion

Like the AVR Arduinos, the M0 library does not have full support for converting floating point numbers to ASCII strings. Functions like sprintf will not convert floating point. Fortunately, the standard AVR-LIBC

library includes the dtostrf function which can handle the conversion for you.

Unfortunately, the M0 run-time library does not have dtostrf. You may see some references to using #include <avr/dtostrf.h> to get dtostrf in your code. And while it will compile, it does not work.

Instead, check out this thread to find a working dtostrf function you can include in your code:

http://forum.arduino.cc/index.php?topic=368720.0 (https://adafru.it/lFS)

How Much RAM Available?

The ATSAMD21G18 has 32K of RAM, but you still might need to track it for some reason. You can do so with this handy function:

extern "C" char *sbrk(int i);

int FreeRam () { char stack_dummy = 0; return &stack_dummy - sbrk(0); }

Thx to http://forum.arduino.cc/index.php?topic=365830.msg2542879#msg2542879 (https://adafru.it/m6D) for the tip!

Storing data in FLASH

If you're used to AVR, you've probably used PROGMEM to let the compiler know you'd like to put a variable or string in flash memory to save on RAM. On the ARM, its a little easier, simply add const before the variable name:

const char str[] = "My very long string";

That string is now in FLASH. You can manipulate the string just like RAM data, the compiler will automatically read from FLASH so you dont need special progmem-knowledgeable functions.

You can verify where data is stored by printing out the address:

Serial.print("Address of str $"); Serial.println((int)&str, HEX);

If the address is $2000000 or larger, its in SRAM. If the address is between $0000 and $3FFFF Then it is in FLASH

Pretty-Printing out registers

There's

a lot

of registers on the SAMD21, and you often are going through ASF or another framework to

get to them. So having a way to see exactly what's going on is handy. This library from drewfish will help a ton!

https://github.com/drewfish/arduino-ZeroRegs (https://adafru.it/Bet)

M4 Performance Options

As of version 1.4.0 of the

Adafruit SAMD Boards

package in the Arduino Boards Manager, some options

are available to wring extra performance out of M4-based devices. These are in the

Tools

menu.

All of these performance tweaks involve a degree of uncertainty. There’s

no guarantee

of improved

performance in any given project, and

some may even be detrimental,

failing to work in part or in whole. If

you encounter trouble, select the default performance settings and re-upload.

Here’s what you get and some issues you might encounter…

CPU Speed (overclocking)

This option lets you adjust the microcontroller core clock…the speed at which it processes instructions… beyond the official datasheet specifications.

Manufacturers often rate speeds conservatively because such devices are marketed for harsh industrial environments…if a system crashes, someone could lose a limb or worse. But most creative tasks are less critical and operate in more comfortable settings, and we can push things a bit if we want more speed.

There is a small but nonzero chance of code locking up or failing to run entirely. If this happens, try dialing back the speed by one notch and re-upload, see if it’s more stable.

Much more likely, some code or libraries may not play well with the nonstandard CPU speed. For example, currently the NeoPixel library assumes a 120 MHz CPU speed and won’t issue the correct data at other settings (this will be worked on). Other libraries may exhibit similar problems, usually anything that strictly depends on CPU timing…you might encounter problems with audio- or servo-related code

depending how it’s written. If you encounter such code or libraries, set the CPU speed to the default 120 MHz and re-upload.

Optimize

There’s usually more than one way to solve a problem, some more resource-intensive than others. Since Arduino got its start on resource-limited AVR microcontrollers, the C++ compiler has always aimed for the smallest compiled program size. The “Optimize” menu gives some choices for the compiler to take different and often faster approaches, at the expense of slightly larger program size…with the huge flash memory capacity of M4 devices, that’s rarely a problem now.

The “Small” setting will compile your code like it always has in the past, aiming for the smallest compiled program size.

The “Fast” setting invokes various speed optimizations. The resulting program should produce the same results, is slightly larger, and usually (but not always) noticably faster. It’s worth a shot!

“Here be dragons” invokes some more intensive optimizations…code will be larger still, faster still, but there’s a possibility these optimizations could cause unexpected behaviors.

Some code may not work the

same as before.

Hence the name. Maybe you’ll discover treasure here, or maybe you’ll sail right off the

edge of the world.

Most code and libraries will continue to function regardless of the optimizer settings. If you do encounter problems, dial it back one notch and re-upload .

Cache

This option allows a small collection of instructions and data to be accessed more quickly than from flash memory, boosting performance. It’s enabled by default and should work fine with all code and libraries. But if you encounter some esoteric situation, the cache can be disabled, then recompile and upload.

Max SPI and Max QSPI

These should probably be left at their defaults. They’re present mostly for our own experiments and can cause serious headaches.

Max SPI determines the clock source for the M4’s SPI peripherals. Under normal circumstances this allows transfers up to 24 MHz, and should usually be left at that setting. But…if you’re using write-only SPI devices (such as TFT or OLED displays), this option lets you drive them faster (we’ve successfully used 60 MHz with some TFT screens). The caveat is, if using

any

read/write devices (such as an SD card),

this will not

work at all…

SPI reads

absolutely

max out at the default 24 MHz setting, and anything else will fail. Write =

OK. Read = FAIL. This is true

even if your code is using a lower bitrate setting…

just having the different

clock source prevents SPI reads.

Max QSPI does similarly for the extra flash storage on M4 “Express” boards.

Very few

Arduino sketches access this storage at all, let alone in a bandwidth-constrained context, so this will benefit next to nobody. Additionally, due to the way clock dividers are selected, this will only provide some benefit when certain “CPU Speed” settings are active. Our PyPortal Animated GIF Display (https://adafru.it/EkO) runs marginally better with it, if using the QSPI flash.

Enabling the Buck Converter on some M4 Boards

If you want to reduce power draw, some of our boards have an inductor so you can use the 1.8V buck converter instead of the built in linear regulator. If the board does have an inductor (see the schematic) you can add the line SUPC->VREG.bit.SEL = 1; to your code to switch to it. Note it will make ADC/DAC

reads a bit noisier so we don't use it by default. You'll save ~4mA (https://adafru.it/F0H).

What is CircuitPython?

CircuitPython is a programming language designed to simplify experimenting and learning to program on low-cost microcontroller boards. It makes getting started easier than ever with no upfront desktop downloads needed. Once you get your board set up, open any text editor, and get started editing code. It's that simple.

CircuitPython is based on Python

Python is the fastest growing programming language. It's taught in schools and universities. It's a highlevel programming language which means it's designed to be easier to read, write and maintain. It supports modules and packages which means it's easy to reuse your code for other projects. It has a built in interpreter which means there are no extra steps, like

compiling

, to get your code to work. And of

course, Python is Open Source Software which means it's free for anyone to use, modify or improve upon.

CircuitPython adds hardware support to all of these amazing features. If you already have Python knowledge, you can easily apply that to using CircuitPython. If you have no previous experience, it's really simple to get started!

Why would I use CircuitPython?

CircuitPython is designed to run on microcontroller boards. A microcontroller board is a board with a

microcontroller chip that's essentially an itty-bitty all-in-one computer. The board you're holding is a microcontroller board! CircuitPython is easy to use because all you need is that little board, a USB cable, and a computer with a USB connection. But that's only the beginning.

Other reasons to use CircuitPython include:

You want to get up and running quickly. Create a file, edit your code, save the file, and it runs immediately. There is no compiling, no downloading and no uploading needed. You're new to programming. CircuitPython is designed with education in mind. It's easy to start learning how to program and you get immediate feedback from the board. Easily update your code. Since your code lives on the disk drive, you can edit it whenever you like, you can also keep multiple files around for easy experimentation. The serial console and REPL. These allow for live feedback from your code and interactive programming. File storage. The internal storage for CircuitPython makes it great for data-logging, playing audio clips, and otherwise interacting with files. Strong hardware support. There are many libraries and drivers for sensors, breakout boards and other external components. It's Python! Python is the fastest-growing programming language. It's taught in schools and universities. CircuitPython is almost-completely compatible with Python. It simply adds hardware support.

This is just the beginning. CircuitPython continues to evolve, and is constantly being updated. We welcome and encourage feedback from the community, and we incorporate this into how we are developing CircuitPython. That's the core of the open source concept. This makes CircuitPython better for you and everyone who uses it!

CircuitPython on Feather M4 Express

CircuitPython (https://adafru.it/tB7) is a derivative of MicroPython (https://adafru.it/BeZ) 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.

The following instructions will show you how to install CircuitPython. If you've already installed CircuitPython but are looking to update it or reinstall it, the same steps work for that as well!

Set up CircuitPython Quick Start!

Follow this quick step-by-step for super-fast Python power :)

https://adafru.it/Emh

Click the link above and download the latest UF2 file.

Download and save it to your desktop (or wherever is handy).

Plug your Feather M4 into your computer using a knowngood USB cable.

A lot of people end up using charge-only USB cables and it is very frustrating! So make sure you have a USB cable you know is good for data sync.

Double-click the Reset button next to the USB connector on your board, and you will see the NeoPixel RGB LED turn green. If it turns red, check the USB cable, try another USB port, etc. Note: The little red LED next to the USB connector will pulse red. That's ok!

If double-clicking doesn't work the first time, try again. Sometimes it can take a few tries to get the rhythm right!

https://adafru.it/Emh

You will see a new disk drive appear called FEATHERBOOT.

Drag the adafruit_circuitpython_etc.uf2 file to

FEATHERBOOT.

The LED will flash. Then, the FEATHERBOOT drive will disappear and a new disk drive called CIRCUITPY will appear.

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

Further Information

For more detailed info on installing CircuitPython, check out Installing CircuitPython (https://adafru.it/Amd).

Installing 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!

Download and Install Mu

Download Mu from https://codewith.mu (https://adafru.it/Be6). Click the Download or Start Here links there for downloads and installation instructions. The website has a wealth of other information, including extensive tutorials and and howto's.

Using 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 is our recommended editor - please use it (unless you are an experienced coder with a favorite editor already!)



Mu attempts to auto-detect your board, so please plug in your CircuitPython device and make sure it shows up as a CIRCUITPY drive before starting 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.

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

Creating and Editing Code

One of the best things about CircuitPython is how simple it is to get code up and running. In this section, we're going to cover 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. We strongly recommend

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 basic text editors built into every operating system such as Notepad on Windows, TextEdit on Mac, and gedit on Linux. However, many of these editors don't write back changes immediately to files that you edit. That can cause problems when using CircuitPython. See the

Editing Code (https://adafru.it/id3) section below. If you want to skip that section for now, 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.)

Creating Code

Open your editor, and create a new file. If you are using Mu, click the New button in the top left

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)

If you're using QT Py or a Trinkey, please download the NeoPixel blink example (https://adafru.it/UDU).

For Adafruit CLUE, you'll need to use board.D17 instead of board.LED . The rest of the code remains the same. Make the following change to the led = line:

led = digitalio.DigitalInOut(board.D17)

For Adafruit ItsyBitsy nRF52840, you'll need to use board.BLUE_LED instead of board.LED . The rest of the code remains the same. Make the following change to the led = line:

led = digitalio.DigitalInOut(board.BLUE_LED)

It will look like this - note that under the while True: line, the next four lines have spaces to indent them, but they're indented exactly the same amount. All other lines have no spaces before the text.

The 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 QT Py or the Trinkeys!



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.



If you are using Adafruit CLUE, you will need to edit the code to use board.D17 as shown below!



If you are using Adafruit ItsyBitsy nRF52840, you will need to edit the code to use board.BLUE_LED as shown below!



Save this file as code.py on your CIRCUITPY drive.

On each board (except the ItsyBitsy nRF52840) you'll find a tiny red LED. On the ItsyBitsy nRF52840, you'll find a tiny blue LED.

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

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

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 just one warning we have to give you before we continue...

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.

There are a few ways to avoid this:

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

Recommended editors:

mu (https://adafru.it/Be6) is an editor that safely writes all changes (it's also our recommended editor!) emacs (https://adafru.it/xNA) is also an editor that will fulIy write files on save (https://adafru.it/Be7)

Sublime Text (https://adafru.it/xNB) safely writes all changes Visual Studio Code (https://adafru.it/Be9) appears to safely write all changes

gedit on Linux appears to safely write all changes

IDLE (https://adafru.it/IWB), in Python 3.8.1 or later, was fixed (https://adafru.it/IWD) to write all changes

immediately

thonny (https://adafru.it/Qb6) fully writes files on save

Recommended

only

with particular settings or with add-ons:

vim (https://adafru.it/ek9) / vi safely writes all changes. But set up vim to not write

swapfiles (https://adafru.it/ELO) (.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 (https://adafru.it/xNC) is safe if "Safe Write" is turned on in Settings->System Settings->Synchronization (true by default). If you are using Atom (https://adafru.it/fMG), install the fsync-on-save

package (https://adafru.it/E9m) so that it will always write out all changes to files on CIRCUITPY .

SlickEdit (https://adafru.it/DdP) works only if you add a macro to flush the disk (https://adafru.it/ven).

Don't Click Reset or Unplug!



We

don't

recommend these editors:

notepad (the default Windows editor) and N otepad++ can be slow to write, so we recommend the editors above! If you are using notepad, be sure to eject the drive (see below)

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 - we haven't tested other editors so please use a recommended one!

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 (https://adafru.it/Den) page of every board guide to get your board up and running again.

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.



Back to Editing Code...

Now! Let's try editing the program you added to your board. Open your code.py file into your editor. We'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? Let's find out!

Exploring Your First CircuitPython Program

First, we'll take a look at the code we'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)

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 modules, 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 in your code. In this example, we 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 any thing extra to make it work! board gives you access to the

hardware on

your board

, digitalio lets you

access that hardware as inputs/outputs

and time let's you pass 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, we initialise that pin, and we set it to output. We set led to equal the rest of that information so we 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.

Inside our loop, we have four items:

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

First, we have led.value = True . This line tells the LED to turn on. On the next line, we 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 time.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 above example to 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.

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

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 to exit the loop.

See also the Behavior section in the docs (https://adafru.it/Bvz).

More Changes

We don't have to stop there! Let's keep going. Change the second 0.5 to 0.1 so it looks like this:

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.txt, code.py, main.txt and main.py. CircuitPython looks for those files, in that order, and then runs the first one it finds. While we suggest using code.py as 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.

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 looks like this:

print("Hello, world!")

This line 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 print those too.

The serial console requires a terminal program. A terminal is a program that gives you a text-based interface to perform various tasks.

sudo apt purge modemmanager

Are you using Mu?

If so, good news! The serial console is built into Mu and will autodetect your board making using the REPL

really really easy

.

Please note that Mu does yet not work with nRF52 or ESP8266-based CircuitPython boards, skip down to the next section for details on using a terminal program.

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, type this command at a shell:

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First, make sure your CircuitPython board is plugged in. If

you are using Windows 7, make sure you installed the drivers (https://adafru.it/Amd).

Once in Mu, look for the Serial button in the menu and click it.

Setting Permissions on Linux

On Linux, if you see an error box something like the one below when you press the Serial 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 Advanced Serial Console on Mac and

Linux (https://adafru.it/AAI) for details on how to add yourself to the right group.

Using Something Else?

If you're not using Mu to edit, are using ESP8266 or nRF52 CircuitPython, or if for some reason you are not a fan of the built in serial console, you can run the serial console as a separate program.

Windows requires you to download a terminal program, check out this page for more details (https://adafru.it/AAH)

Mac and Linux both have one built in, though other options are available for download, check this page for more details (https://adafru.it/AAI)

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, we'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.

Excellent! Our print statement is showing up in our console! Try changing the printed text to something else.

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 we can see how it is used.

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

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. We 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.

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. 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.

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, 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.

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 there is no code running, you will enter the REPL immediately after pressing Ctrl + C. There is no information about what your board was doing before you interrupted it because there is no code running.

Either way, 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.

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.

From this prompt you can run all sorts of commands and code. The first thing we'll do is run help() . This will tell us 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, please do

`help("modules")`. Remember the libraries 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.

This is a list of all the core libraries built into CircuitPython. We discussed how 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." We're going to say hello to something else. Type into the REPL:

print("Hello, CircuitPython!")

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. As we said though, 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 libraries are available and explore those libraries.

Try typing more into the REPL to see what happens!

Returning to the serial console

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

CircuitPython 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. 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 awesome 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 (https://adafru.it/rar) are a great reference for how it all should work. In Python terms, we 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, we provide a bundle full of our

As we continue to develop CircuitPython and create new releases, we 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.



libraries.

Our bundle and releases 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.

Installing the CircuitPython Library Bundle

We're constantly updating and improving our libraries, so we don't (at this time) ship our CircuitPython boards with the full library bundle. Instead, you can find example code in the guides for your board that depends on external libraries. Some of these libraries may be available from us at Adafruit, some may be written by community members!

Either way, as you start to explore CircuitPython, you'll want to know how to get libraries on board.

You can grab the latest Adafruit CircuitPython Bundle release by clicking the button below.

Note: Match up the bundle version with the version of CircuitPython you are running - 3.x library for running any version of CircuitPython 3, 4.x for running any version of CircuitPython 4, etc. If you mix libraries with major CircuitPython versions, you will most likely get errors due to changes in library interfaces possible during major version changes.

https://adafru.it/ENC

If you need another version, you can also visit the bundle release page (https://adafru.it/Ayy) which will let you select exactly what version you're looking for, as well as information about changes.

Either way, download the version that matches your CircuitPython firmware version. If you don't know the version, look at the initial prompt in the CircuitPython REPL, which reports the version. For example, if you're running v4.0.1, download the 4.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.

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.

https://adafru.it/ENC

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, 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.

Copying Libraries to Your Board

First you'll want to create a lib folder on your CIRCUITPY drive. Open the drive, right click, choose the option to create a new folder, and call it lib. 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.

This also applies to example files. They are only supplied as raw .py files, so they may need to be converted to .mpy using the mpy-cross utility if you encounter MemoryErrors . This is discussed in the

CircuitPython Essentials Guide (https://adafru.it/CTw). Usage is the same as described above in the

Express Boards section. Note: If you do not place examples in a separate folder, you would remove the examples from the import statement.

Example: ImportError Due to Missing Library

If you choose to load libraries as you need them, you may write up code that tries to use a library you haven't yet loaded. We're going to 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 blinky example.

import board import time import simpleio

led = simpleio.DigitalOut(board.D13)

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.

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



We have an ImportError . It says there is no module named 'simpleio' . That's the one we just included in our 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 we'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 a Trinket M0 or Gemma M0, you'll want to follow the same steps in the example above to install libraries as you need them. You don't always need to wait for an ImportError as you probably know

what library you added to your code. Simply open the lib folder you downloaded, find the library you need, and drag it to the lib folder on your CIRCUITPY drive.

You may end up running out of space on your Trinket M0 or Gemma M0 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 them in the Troubleshooting page in the Learn guides for your board.

Updating CircuitPython Libraries/Examples

Libraries and examples are updated from time to time, and it's important to update the files you have on your CIRCUITPY drive.

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.



Frequently Asked Questions

These are some of the common questions regarding CircuitPython and CircuitPython microcontrollers.

I have to continue using an older version of CircuitPython; where can I find compatible libraries?

We are no longer building or supporting library bundles for older versions of CircuitPython. We highly encourage you to update CircuitPython to the latest version (https://adafru.it/Em8) and use the current

version of the libraries (https://adafru.it/ENC). However, if for some reason you cannot update, here are

points to the last available library bundles for previous versions:

2.x (https://adafru.it/FJA)

3.x (https://adafru.it/FJB)

4.x (https://adafru.it/QDL)

5.x (https://adafru.it/QDJ)

Is ESP8266 or ESP32 supported in CircuitPython? Why not?

We dropped ESP8266 support as of 4.x - For more information please read about it here!

https://learn.adafruit.com/welcome-to-circuitpython/circuitpython-for-esp8266 (https://adafru.it/CiG)

We do not support ESP32 because it does not have native USB. We do support ESP32-S2, which does.

As we continue to develop CircuitPython and create new releases, we 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.



How do I connect to the Internet with CircuitPython?

If you'd like to add WiFi support, check out our guide on ESP32/ESP8266 as a coprocessor. (https://adafru.it/Dwa)



Is there asyncio support in CircuitPython?

We do not have asyncio support in CircuitPython at this time. However, async and await are turned on in many builds, and we are looking at how to use event loops and other constructs effectively and

easily.



My RGB NeoPixel/DotStar LED is blinking funny colors - what does it mean?

The status LED can tell you what's going on with your CircuitPython board. Read more here for what the

colors mean! (https://adafru.it/Den)

What is a MemoryError ?

Memory allocation errors happen when you're trying to store too much on the board. The CircuitPython microcontroller boards have a limited amount of memory available. You can have about 250 lines of code on the M0 Express boards. If you try to import too many libraries, a combination of large libraries, or run a

program with too many lines of code, your code will fail to run and you will receive a MemoryError in the serial console (REPL).

What do I do when I encounter a MemoryError ?

Try resetting your board. Each time you reset the board, it reallocates the memory. While this is unlikely to

resolve your issue, it's a simple step and is worth trying.

Make sure you are using .mpy versions of libraries. All of the CircuitPython libraries are available in the bundle in a .mpy format which takes up less memory than .py format. Be sure that you're using the latest

library bundle (https://adafru.it/uap) for your version of CircuitPython.

If that does not resolve your issue, try shortening your code. Shorten comments, remove extraneous or unneeded code, or any other clean up you can do to shorten your code. If you're using a lot of functions, you could try moving those into a separate library, creating a .mpy of that library, and importing it into your

code.

You can turn your entire file into a .mpy and import that into code.py . This means you will be unable to edit your code live on the board, but it can save you space.

Can the order of my import statements affect memory?

It can because the memory gets fragmented differently depending on allocation order and the size of objects. Loading .mpy files uses less memory so its recommended to do that for files you aren't editing.

How can I create my own .mpy files?

You can make your own .mpy versions of files with mpy-cross .

You can download mpy-cross for your operating system from https://adafruit-circuit-

python.s3.amazonaws.com/index.html?prefix=bin/mpy-cross/ (https://adafru.it/QDK). Builds are available for

Windows, macOS, x64 Linux, and Raspberry Pi Linux. Choose the latest `mpy-cross` whose version matches the version of CircuitPython you are using.

To make a .mpy file, run ./mpy-cross path/to/yourfile.py to create a yourfile.mpy in the same directory as the original file.

How do I check how much memory I have free?

import gc gc.mem_free()

Will give you the number of bytes available for use.

Does CircuitPython support interrupts?

No. CircuitPython does not currently support interrupts. We do not have an estimated time for when they will be included.

Does Feather M0 support WINC1500?

No, WINC1500 will not fit into the M0 flash space.

Can AVRs such as ATmega328 or ATmega2560 run CircuitPython?

No.

Commonly Used Acronyms

CP or CPy = CircuitPython (https://adafru.it/cpy-welcome) CPC = Circuit Playground Classic (https://adafru.it/ncE) CPX = Circuit Playground Express (https://adafru.it/wpF)

Welcome to the Community!

CircuitPython is a programming language that's super simple to get started with and great for learning. It runs on microcontrollers and works out of the box. You can plug it in and get started with any text editor. The best part? CircuitPython comes with an amazing, supportive community.

Everyone is welcome! CircuitPython is Open Source. This means it's available for anyone to use, edit, copy and improve upon. This also means CircuitPython becomes better because of you being a part of it. It doesn't matter whether this is your first microcontroller board or you're a computer engineer, you have something important to offer the Adafruit CircuitPython community. We're going to highlight some of the many ways you can be a part of it!

Adafruit Discord

The Adafruit Discord server is the best place to start. Discord is where the community comes together to volunteer and provide live support of all kinds. From general discussion to detailed problem solving, and everything in between, Discord is a digital maker space with makers from around the world.

There are many different channels so you can choose the one best suited to your needs. Each channel is shown on Discord as "#channelname". There's the #help-with-projects channel for assistance with your current project or help coming up with ideas for your next one. There's the #showandtell channel for showing off your newest creation. Don't be afraid to ask a question in any channel! If you're unsure, #general is a great place to start. If another channel is more likely to provide you with a better answer, someone will guide you.

The help with CircuitPython channel is where to go with your CircuitPython questions. #help-withcircuitpython is there for new users and developers alike so feel free to ask a question or post a comment! Everyone of any experience level is welcome to join in on the conversation. We'd love to hear what you have to say! The #circuitpython channel is available for development discussions as well.

The easiest way to contribute to the community is to assist others on Discord. Supporting others doesn't always mean answering questions. Join in celebrating successes! Celebrate your mistakes! Sometimes just hearing that someone else has gone through a similar struggle can be enough to keep a maker moving forward.

The Adafruit Discord is the 24x7x365 hackerspace that you can bring your granddaughter to.

Visit https://adafru.it/discord ()to sign up for Discord. We're looking forward to meeting you!

Adafruit Forums

The Adafruit Forums (https://adafru.it/jIf) are the perfect place for support. Adafruit has wonderful paid support folks to answer any questions you may have. Whether your hardware is giving you issues or your code doesn't seem to be working, the forums are always there for you to ask. You need an Adafruit account to post to the forums. You can use the same account you use to order from Adafruit.

While Discord may provide you with quicker responses than the forums, the forums are a more reliable source of information. If you want to be certain you're getting an Adafruit-supported answer, the forums are the best place to be.

There are forum categories that cover all kinds of topics, including everything Adafruit. The Adafruit

CircuitPython and MicroPython (https://adafru.it/xXA) category under "Supported Products & Projects" is

the best place to post your CircuitPython questions.

Be sure to include the steps you took to get to where you are. If it involves wiring, post a picture! If your code is giving you trouble, include your code in your post! These are great ways to make sure that there's enough information to help you with your issue.

You might think you're just getting started, but you definitely know something that someone else doesn't. The great thing about the forums is that you can help others too! Everyone is welcome and encouraged to provide constructive feedback to any of the posted questions. This is an excellent way to contribute to the community and share your knowledge!

Adafruit Github

Whether you're just beginning or are life-long programmer who would like to contribute, there are ways for everyone to be a part of building CircuitPython. GitHub is the best source of ways to contribute to

CircuitPython (https://adafru.it/tB7) itself. If you need an account, visit https://github.com/

(https://adafru.it/d6C)and sign up.

If you're new to GitHub or programming in general, there are great opportunities for you. Head over to

adafruit/circuitpython (https://adafru.it/tB7) on GitHub, click on "Issues (https://adafru.it/Bee)", and you'll find

a list that includes issues labeled "good first issue (https://adafru.it/Bef)". These are things we've identified as something that someone with any level of experience can help with. These issues include options like updating documentation, providing feedback, and fixing simple bugs.

Already experienced and looking for a challenge? Checkout the rest of the issues list and you'll find plenty of ways to contribute. You'll find everything from new driver requests to core module updates. There's plenty of opportunities for everyone at any level!

When working with CircuitPython, you may find problems. If you find a bug, that's great! We love bugs! Posting a detailed issue to GitHub is an invaluable way to contribute to improving CircuitPython. Be sure to include the steps to replicate the issue as well as any other information you think is relevant. The more detail, the better!

Testing new software is easy and incredibly helpful. Simply load the newest version of CircuitPython or a library onto your CircuitPython hardware, and use it. Let us know about any problems you find by posting a new issue to GitHub. Software testing on both current and beta releases is a very important part of contributing CircuitPython. We can't possibly find all the problems ourselves! We need your help to make CircuitPython even better.

On GitHub, you can submit feature requests, provide feedback, report problems and much more. If you have questions, remember that Discord and the Forums are both there for help!

ReadTheDocs

ReadTheDocs (https://adafru.it/Beg) is a an excellent resource for a more in depth look at CircuitPython.

This is where you'll find things like API documentation and details about core modules. There is also a Design Guide that includes contribution guidelines for CircuitPython.

RTD gives you access to a low level look at CircuitPython. There are details about each of the core

modules (https://adafru.it/Beh). Each module lists the available libraries. Each module library page lists the

available parameters and an explanation for each. In many cases, you'll find quick code examples to help you understand how the modules and parameters work, however it won't have detailed explanations like

the Learn Guides. If you want help understanding what's going on behind the scenes in any CircuitPython code you're writing, ReadTheDocs is there to help!

Advanced Serial Console on Windows

Windows 7 Driver

If you're using Windows 7, use the link below to download the driver package. You will not need to install drivers on Mac, Linux or Windows 10.

https://adafru.it/AB0

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.

We'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.

https://adafru.it/AB0

Adafruit Feather M4 Express User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual