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.

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.

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

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'

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

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.