add satrx-example for stm32f3-disco here

satrs-example-stm32f3-disco/README.md

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+sat-rs example for the STM32F3-Discovery board
+=======
+
+This example application shows how the [sat-rs framework](https://egit.irs.uni-stuttgart.de/rust/satrs-launchpad)
+can be used on an embedded target. It also shows how a relatively simple OBSW could be built when no
+standard runtime is available. It uses [RTIC](https://rtic.rs/1/book/en/) as the concurrency
+framework.
+
+The STM32F3-Discovery device was picked because it is a cheap Cortex-M4 based device which is also
+used by the [Rust Embedded Book](https://docs.rust-embedded.org/book/intro/hardware.html) and the
+[Rust Discovery](https://docs.rust-embedded.org/discovery/f3discovery/) book as an introduction
+to embedded Rust.
+
+## Preparing Rust and the repository
+
+Building an application requires the `thumbv7em-none-eabihf` cross-compiler toolchain.
+If you have not installed it yet, you can do so with
+
+```sh
+rustup target add thumbv7em-none-eabihf
+```
+
+A default `.cargo` config file is provided for this project, but needs to be copied to have
+the correct name. This is so that the config file can be updated or edited for custom needs
+without being tracked by git.
+
+```sh
+cp def_config.toml config.toml
+```
+
+The configuration file will also set the target so it does not always have to be specified with
+the `--target` argument.
+
+## Building
+
+After that, assuming that you have a `.cargo/config.toml` setting the correct build target,
+you can simply build the application with
+
+```sh
+cargo build
+```
+
+## Flashing and Debugging from the command line
+
+TODO
+
+## Debugging with VS Code
+
+The STM32F3-Discovery comes with an on-board ST-Link so all that is required to flash and debug
+the board is a Mini-USB cable. The code in this repository was debugged using `openocd`
+and the VS Code [`Cortex-Debug` plugin](https://marketplace.visualstudio.com/items?itemName=marus25.cortex-debug).
+
+Some sample configuration files for VS Code were provided as well. You can simply use `Run` and `Debug`
+to automatically rebuild and flash your application.
+
+The `tasks.json` and `launch.json` files are generic and you can use them immediately by opening
+the folder in VS code or adding it to a workspace.
+
+If you would like to use a custom GDB application, you can specify the gdb binary in the following
+configuration variables in your `settings.json`:
+
+- `"cortex-debug.gdbPath"`
+- `"cortex-debug.gdbPath.linux"`
+- `"cortex-debug.gdbPath.windows"`
+- `"cortex-debug.gdbPath.osx"`
+
+## Commanding with Python
+
+When the SW is running on the Discovery board, you can command the MCU via a serial interface,
+using COBS encoded CCSDS packets.
+ 
+TODO:
+  - How and where to connect serial interface on the MCU
+  - How to set up Python venv (or at least strongly recommend it) and install deps
+  - How to copy `def_tmtc_conf.json` to `tmtc_conf.json` and adapt it for custom serial port