flxzt / gestures_w_rust

gestures_w_rust

This project features a simple gesture recognition library that processes depth measurements coming from the low resolution TOF-Sensor "ST VL53L5CX".

It showcases integration of a Rust library into an Embedded-C STM32CubeIDE codebase.

The device is configured as HID device, and reports the recognized gestures to the USB host.

Connection:

• AVdd must be connected to a 5V power rail
• IOVdd must be connected to a 3.3V power rail

Connect the other pins as documented in the CubeMX report.

wave Rust crate

The library and bindings can be (re)built with cargo build --release --target=thumbv7em-none-eabihf.

Cbindgen is needed to (re)generate the header file. To install execute cargo install --force cbindgen.

The bindings are one header wave.h in the library root directory and the static lib libwave.a located in target/release

The library is rebuilt by the prebuild_debug.sh / prebuild_release.sh scripts, which are automatically executed as a pre-build step in the STM32CubeIDE project.

Debugging

It is possible to debug the rust library with gdb. Simply compile with debugging symbols by setting debug = true in the cargo [profile.dev] profile and build it wihtout the --release flag. It might be necessary to optimize for binary size as well, depending on the memory constraints on the MCU: opt-level = "s".

Then build the binary in STM32CubeIDE (also with the debug profile).

You can either launch the stlink gdb-server with STM32CubeIDE and attach to it from the terminal or VSCode, or launch a gdb-server yourself.

To enable debugging in vscode, the Cortex-Debug extension can be used.

To connect to the gdb-server launched with STM32CubeIDE, first take a look at the debug configuration, it should look like this:

Remember the port. Also only one debug session can be attached at a time, so it is necessary to detach the on in STM32CubeIDE first.

A configuration in VSCode could look like this:

        {
            "name": "Attach to gdb-server and start debugging gesture_w_rust",
            "cwd": "${workspaceFolder}",
            "executable": "${workspaceFolder}/Debug/gestures_w_rust.elf",
            "gdbPath": "gdb",
            "request": "attach",
            "type": "cortex-debug",
            "servertype": "stlink",
            "gdbTarget": "localhost:61234"
        }

To start an own instance of a stlink gdb-server, write an entry that looks like this:

        {
            "name": "Debug gesture_w_rust",
            "cwd": "${workspaceFolder}",
            "executable": "${workspaceFolder}/Debug/gestures_w_rust.elf",
            "gdbPath": "gdb",
            "request": "launch",
            "type": "cortex-debug",
            "servertype": "stlink",
        }

HID device

The gestures are reported as HID keyboard keypresses:

• GestureSwipeRight: ArrowRight
• GestureSwipeLeft: ArrowLeft
• GestureSwipeDown: ArrowDown
• GestureSwipeUp: ArrowUp
• GestureHold: Space