Raspberry Pi Pico example

This repository contains the scaffolding for programming and debugging a Raspberry Pi Pico or Pico W.

It currently has a simple demo program that reads the raw angle from an AS5048A magnetic rotary position sensor over SPI and emits some output via UART and an LED.

Instructions

Preliminaries

Install the following tools:

• GDB (e.g., with brew install arm-none-eabi-gdb)
• Minicom (e.g., with brew install minicom)
• OpenOCD (e.g., with brew install openocd)
• Toast (e.g., with brew install toast)

Then initialize the submodules with:

git submodule update --init
(cd pico-sdk && git submodule update --init)

Note: It might be tempting to just run git submodule update --init --recursive, but that would take a long time and download more submodules than necessary.

Build the project

You can build the project by running toast. This will produce two output files: out.elf and out.uf2.

Program the Raspberry Pi Pico

There are two ways to flash the code onto the microcontroller. The first way is via USB:

1. Plug the Raspberry Pi Pico into a USB port while holding the BOOTSEL button.

2. Run this command, adjusting the path to the device as necessary:

   cp image.uf2 /Volumes/RPI-RP2/

The code is now running. To flash new code, unplug the Pico and start again.

The second way to program it is with a Raspberry Pi Debug Probe that is connected to the Pico's SWD debug port:

openocd -f interface/cmsis-dap.cfg -f target/rp2040.cfg -c 'adapter speed 5000; program out.elf verify reset exit'

If you want to restart the code without reprogramming the microcontroller, run:

openocd -f interface/cmsis-dap.cfg -f target/rp2040.cfg -c 'adapter speed 5000; init; reset; exit'

Debug the code with a Raspberry Pi Debug Probe

To debug the code, first build the code in debug mode:

BUILD_TYPE=Debug toast

Then flash the code onto the Raspberry Pi Pico with the instructions above.

Now run the following command to start GDB servers:

openocd -f interface/cmsis-dap.cfg -f target/rp2040.cfg -c 'adapter speed 5000'

Then start GDB:

arm-none-eabi-gdb

Attach to one of the two cores with core0 or core1. At this point the program will pause. The following commands are helpful:

• continue (c): Resume execution
• ^C: Pause execution
• next (n): Execute one step, treating subroutines as a single step
• step (s): Execute one step, including individual steps in subroutines
• print x (p x): Print the value of the variable named x
• break (b): Set a breakpoint
• delete (d): Delete a breakpoint
• disable: Disable a breakpoint
• enable: Enable a breakpoint
• list . (l .): Show the code at the current location
• where: Show the current stack trace
• finish: Run the current function to completion
• quit (q): Quit

Run a serial console

You can use a serial console to connect to the Raspberry Pi Pico or a Raspberry Pi Debug Probe connected to the Pico's UART pins:

1. Run Minicom, adjusting the path to the device as necessary:

   minicom --device /dev/tty.usbmodem*
   

2. Press Meta + Q to quit.