Created: 2023-08-05Updated: 2024-01-23

Raspberry Pi Pico no Hands Flashing

Contents

Picotool
Pico Preperations
No-Hands Flashing
Going Further

Today we're gonna check out how to use picotool to flash our Raspberry Pi Pico without unplugging it.

This tutorial is based on a previous article, so make sure to consult the first part if the general SDK setup is unclear.

Picotool

First things first we have to clone the picotool repository

          git clone https://github.com/raspberrypi/picotool.git

and make sure to have libusb installed. On macOS we can do this via the brew package manager:

          brew install libusb

After that is done we can build the picotool binary. Let's switch into the picotool directory and execute the following commands to create a build folder, export the path to our pico-sdk project and finally build the binary.

          mkdir build
          cd build
          export PICO_SDK_PATH=<your path to the pico-sdk directory>
          cmake ..
          make

After the compilation has finished we have our finished picotool binary in our build folder. We can verify our build by running picotool's help command:

          ./picotool help

If you're feeling fancy you can add the picotool binary to your PATH for maximum efficiency gains.

Pico Preperations

To enable our Raspberry Pi Pico to be restarted via USB while running we need to flash it once manually with a binary enables standard I/O via USB. This feature can be enabled in your CMakeLists.txt file via the pico_enable_stdio_usb drective (an example can be found here).

Rebuild our project and we are all set.

Also make sure that your main function contains a call to stdio_init_all(). Otherwise the USB functionality won't be initialized and the next steps won't work.

No-Hands Flashing

Now the last step to greatness is to keep our Rasberry Pi Pico plugged in, point the picotool load command to our .uf2 file and off we go:

          picotool load -f <path to .uf2 file>

The -f flag forces the Pico into BOOTSEL mode even though it is currently running. This is only possible when you build all your binaries with pico_enable_stdio_usb.

Congrats! Another step towards ultimate laziness (aka efficiency) has been taken and we no longer need to move away from our beloved keyboard to mingle with those pesky cables.

Going Further

This is all nice and well but there is still some room to improve this setup. We still have to build our code on every change and then flash our microcontroller via the picotool command. Two steps that definitely could be one...

To have an even tighter integration into our build process we can add the picotool execution into a custom Makefile that in turn depends on our .uf2 file being up-to-date and rebuilds it automatically on changes. I'm not going into too much detail here but instead just point you to one of my projects that uses it in a similar way.