pico-ssm

RP2040 bindings for sslang and its ssm-runtime.

Dependencies

You will need the Sslang compiler, sslc, to generate SSM programs that link against the ssm-runtime. You should build and install it from source, and make it available on your PATH. (Alternatively, you may patch the CMakeLists.txt to point directly to where sslc is installed.)

This project needs to be built using Raspberry Pi's Pico SDK. We've vendored that library in this repo so you won't need to obtain it separately, but you will need to install its dependencies yourself:

macOS

Install CMake and the Arm Embedded Toolchain:

brew install cmake
brew install --cask gcc-arm-embedded

Ubuntu/Debian

sudo apt install cmake gcc-arm-none-eabi libnewlib-arm-none-eabi libstdc++-arm-none-eabi-newlib

If you want to use GDB for debugging, also install the multi-architecture version:

sudo apt install gdb-multiarch

Building

Just Run Make™:

make

The top-level Makefile handles setting up the build directory and invoking the build command, all using CMake. CMake automatically handles initializing this repo's Git submodules (containing pico-sdk and ssm-runtime), and also sets the PICO_SDK_PATH variable that tells CMake where pico-sdk can be found.

Directory Organization

• ssm-rp2040/: contains the SSM runtime bindings for the RP2040 platform, including .pio files implementing PIO state machine code.

• programs/: contains a collection of Sslang programs, which it automatically builds using sslc. You may write your own Sslang programs and add them here. Note that some of the Sslang programs have hard-coded GPIO pin numbers, which you may want to adjust according to the RP2040 hardware you are using.

• lib/: contains external dependencies, added as Git submodules. CMakeLists.txt declares ssm-runtime as a CMake library that is statically linked into the main program.

• tests/: a collection of test suites created during the development process. Overdue for cleanup.

• cmake/: contains additional .cmake files used by the top-level CMakeLists.txt file.

• gdb/: contains sample .gdbinit files.

• build/: CMake puts all build artifacts in here. This directory should not be tracked by version control.

Running

If you have your Pico connected to your machine via the USB port, you can boot it in bootloader mode (power it on while holding the BOOTSEL button). It should appear as a mountable disk drive, in which you can place the compiled .uf2 file to flash the microcontroller. You can also automate this process using the picotool provided by Raspberry Pi (I recommend compiling and installing it from source so that it is on your PATH).

Alternatively, if you have your Pico connected to a debug probe via SWD, you can flash it using tools like pyOCD or OpenOCD. For instance, with pyOCD, the command to do so is:

pyocd flash -t rp2040 <.elf-file>

The pyOCD command is provided as a Make target for convenience:

make flash

NOTE The default UART baud rate is 115200, with TX on GP0 and RX on GP1.