Adafruit RP2040 PIO User Manual

An Introduction to RP2040 PIO with CircuitPython

Created by Jeff Epler

Last updated on 2021-05-03 11:50:57 AM EDT

2 3

3 3 3 4 4

7

7 8

9 9

9 11 12

13

16

17

19

20

23

23 25 25

29 30

Guide Contents

Guide Contents Overview

Major differences between adafruit_pioasm and standard pioasm .wrap and .wrap_target are not supported mov operator restrictions Expressions are not supported Products

Installing CircuitPython

CircuitPython Quickstart Flash Resetting UF2

Installing Mu Editor Download and Install Mu Using Mu Installing Libraries Using PIO to turn an LED on and off

Code Walkthrough

Using PIO to control LED brightness

Code Walkthrough

Using PIO to blink a LED quickly or slowly

Code Walkthrough

Using PIO to drive a NeoPixel

Parts Full Code Listing Code Walk-through

API Documentation: adafruit_pioasm API Documentation: rp2pio

Overview

A feature that sets the Raspberry Pi Foundation RP2040 microcontroller apart from other microcontrollers is "PIO". The RP2040 datasheet says that the "programmable input/output block (PIO) is a versatile hardware interface. It can support a variety of IO standards… PIO is programmable in the same sense as a processor."

In this guide, you'll learn how to write and use PIO programs from CircuitPython. The official

datasheet (https://adafru.it/QLC) (chapter 3), the book "Get Started with MicroPython on Raspberry Pi Pico" (https://adafru.it/QLD) and pico-examples (https://adafru.it/Qa2) (pio folder) are helpful resources too,

but CircuitPython sometimes deviates from the way that PIO is used in other environments like C or MicroPython.

 Examples in this guide require CircuitPython 6.2.0-beta.3 or later, or the Absolute Latest version.

Major differences between adafruit_pioasm and standard pioasm



.wrap and .wrap_target are not supported

Instead, an implicit .wrap is at the bottom of every program, and an implicit .wrap_target is at the top of every program. You can add a jmp instruction instead of using .wrap but remember that this slightly changes the instruction length and the timing of your pio program.



mov operator restrictions

The mov instruction can accept an optional argument, called an operator, to reverse ( :: ) or invert ( ~ ) its argument. In adafruit_pioasm, one or more spaces must come between the :: or ~ and the operand.

These spaces are not required by the official dialect.

The official dialect allows "!" to mean the same as "~". This is not accepted by adafruit_pioasm.



Expressions are not supported

Standard pioasm supports expressions like [T1 + 1] . In pioasm, calculations are not supported. Instead, use string formatting operations to insert the computed value where necessary, e.g., f"""…[{T1+ 1}]…"""

Products

These examples were designed for the Raspberry Pi Pico but can be adapted to the range of boards with the RP2040 microcontroller. The QT Py RP2040 requires the addition of an external LED and currentlimiting resistor for the standard LED examples.

Adafruit Feather RP2040

A new chip means a new Feather, and the Raspberry Pi RP2040 is no exception. When we saw this chip we thought "this chip is going to be awesome when we give it the Feather... Out of Stock

Your browser does not support the video tag. Adafruit ItsyBitsy RP2040

A new chip means a new ItsyBitsy, and the Raspberry Pi RP2040 is no exception. When we saw this chip we thought "this chip is going to be awesome when we give it the ItsyBitsy... $9.95 In Stock

Out of

Stock

Add to Cart

Your browser does not support the video tag. Adafruit QT Py RP2040

What a cutie pie! Or is it... a QT Py? This diminutive dev board comes with one of our new favorite chip, the RP2040. It's been made famous in the new $9.95 In Stock

Raspberry Pi Pico RP2040

The Raspberry Pi foundation changed single-board computing when they released the Raspberry Pi computer, now they're ready to... Out of Stock

Add to Cart

Out of

Stock

Raspberry Pi Pico RP2040

The Raspberry Pi foundation changed single-board computing when they released the Raspberry Pi computer, now they're ready to... Out of Stock

Out of

Stock

Installing CircuitPython

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.

CircuitPython Quickstart

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

https://adafru.it/QaP

Click the link above and download the latest UF2 file.

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

Start with your Pico unplugged from USB. Hold down the BOOTSEL button, and while continuing to hold it (don't let go!), plug the Pico into USB. Continue to hold the BOOTSEL

button until the RPI-RP2 drive appears!

If the drive does not appear, unplug your Pico and go through the above process again.

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.

https://adafru.it/QaP

You will see a new disk drive appear called RPI-RP2.

Drag the adafruit_circuitpython_etc.uf2 file to RPI-RP2.

The RPI-RP2 drive will disappear and a new disk drive called CIRCUITPY will appear.

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

Flash Resetting UF2

If your Pico ever gets into a really

weird

state and doesn't even show up as a disk drive when installing CircuitPython, try installing this 'nuke' UF2 which will do a 'deep clean' on your Flash Memory. You will lose all the files on the board, but at least you'll be able to revive it! After nuking, re-install CircuitPython

https://adafru.it/QAJ

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!

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

Download and Install Mu

Download Mu from https://codewith.mu (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 how-to'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 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...

Adafruit RP2040 PIO User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual