eps

EPS Software

This repo contains rust code to run on the PMIC of the EPS for 1KCubeSat project. Hardware design files of the EPS can be found in the 1KCubeSat Hardware repo

• EPS stands for Electrical Power (Sub)System
• PMIC stands for Power Managment IC

The PMIC on this EPS is the STM32L496ZG.

Why Rust?

C and C++ based development for STM32 platforms is very well established, and is something I have done before. Rust provided the perfect opportunity to try something new.

Tooling setup with VSCode (Highlevel)

• The Cortex-Debug extension in VSCode provides the wrapper around GDB for debugging and stepping through the code.
• See .vscode/launch.json for Cortex-Debug launch configurations
• See ../svd/ for SVD register description files for STM32 devices.
• OpenOCD is the Debugger, and OpenOCD uses STLink to flash the STM32.
• OpenOCD opens a port for GDB to connect
• See ../openocd_cfg/ for OpenOCD configuration files.

Actually getting the above tooling to work

This is my repo, so I'll get on my soapbox.

OpenOCD isn't hard to download, build and install, but the OpenOCD.cfg files are a mess. Instead of writing my own, or being able to easily finding one online, I just copied the .cfg out of my SW4STM32 (an eclipse based editor for writing C code for STM32) IDE's plugin path. Great! I have a .cfg for OpenOCD, but it only works with the SW4STM32 version of OpenOCD. The SW4STM32 version runs a dirty version of v0.10.0, (v0.10.0-dev-00021-g524e8c8 specifically). Not sure what's going on there, but the same .cfg does NOT work with a clean v0.10.0 of OpenOCD downloaded from the link above. Here's what I've had to do in order to use OpenOCD.

• All OpenOCD config files that came with SW4STM32 can be found in a subdirectory here
• Change my VSCode global settings.json to include "cortex-debug.openocdPath": "/path/to/Ac6/SystemWorkbench/plugins/fr.ac6.mcu.externaltools.openocd.linux64_1.23.0.201904120827/tools/openocd/bin/openocd"
• Modify my ldconfig settings to include dynamic libraries so the above binary would run.

Manually install on target MCU

If all else fails, here's a manual way to flash your micro

cargo build --release
arm-none-eabi-objcopy -O binary target/thumbv7em-none-eabihf/release/eps out.bin
st-flash --debug --reset --freq=100K write out.bin 0x8000000

Protobuf setup

I use Google Protocol buffers (protobuf) to send messages back and forth from this microcontroller. To make this work with Rust, and in a no-std environment, I use quick-protobuf. This library allows me to set default-features=false which disables reliance on std. Using the provided pb-rs code generator, I can write .proto protobuf specifications.

• src/messages.proto contains the protobuf definition.
• pb-rs is installed via cargo install pb-rs
• Call pb-rs src/messages.proto to generate files. These should be generated in a subfolder of src/, and can be included into the project.
• Note that quick-protobuf requires an allocator, which I supply using alloc_cortex_m.

cortex-m-quickstart

See the cortex-m-quickstart repository for a template used to generate this repo

Pictures