Pixracer Pro BMI08x identity probe¶

Pixracer Pro boards may contain either a BMI085 or BMI088 accelerometer. The two variants report different chip IDs and support different acceleration ranges, so the firmware must select the matching range conversion. The standalone bmi08x_id_probe executable reads the accelerometer chip ID over SPI5 without starting the flight-control firmware or PWM outputs.

The probe source is in boards/pixracerpro/src/bin/bmi08x_id_probe.rs. It is a separate Cargo binary: the normal cargo xtask flash-board pixracerpro path explicitly builds and flashes only --bin veloxity. This Markdown file and the probe executable are therefore not included in the normal flight-firmware image.

Connect and identify the debug probe¶

Connect the SWD debugger and power the Pixracer Pro, then verify that probe-rs can see it:

probe-rs list

The procedure works with a supported J-Link or ST-Link. The board used to validate this probe was connected through an ST-Link V2.

Build the identity probe¶

From the Veloxity repository root, run:

cargo build -p pixracerpro \
  --target thumbv7em-none-eabihf \
  --bin bmi08x_id_probe \
  --release \
  --no-default-features \
  --features mcu-h743ii

This produces target/thumbv7em-none-eabihf/release/bmi08x_id_probe.

Flash and read the result¶

Run the probe under probe-rs so its semihosting message appears in the terminal:

probe-rs run \
  --chip STM32H743IIKx \
  --protocol swd \
  --speed 4000 \
  target/thumbv7em-none-eabihf/release/bmi08x_id_probe

Interpret the result as follows:

The tested Pixracer Pro reported:

Pixracer BMI08x probe: ID 0x1F => BMI085

The result is also stored in the debugger-visible PIXRACER_BMI_ACCEL_ID atomic. An SPI failure stores 0xFFFFFFFE; the initial value before a completed read is 0xFFFFFFFF.

The requested 4000 kHz SWD speed is an upper request, not a guarantee. probe-rs may report that the connected debugger negotiated a lower speed; this does not change the sensor result.

Press Ctrl-C after reading the message.

Restore the flight firmware¶

The identity probe replaces the firmware currently in flash and intentionally does not run Veloxity. Always restore the normal flight firmware before using the board:

cargo xtask flash-board pixracerpro

That command builds and flashes only the optimized veloxity binary, verifies the programmed image, and resets the Pixracer Pro.