Firmware build

Compile and run the Rust firmware on opentag U1 V2 with the repository-pinned Embassy tree.

Current source checkout required.

The current STM32 firmware is not in the public website repository. Request source access from hello@open-tags.com. A supplied checkout must include firmware/rust_bringup/stm32g4 and the pinned firmware/embassy dependency. For normal setup, use the browser quickstart; building is optional.

Toolchain

Install Rust first. From the supplied checkout's root, initialize the required submodule and enter the firmware package:

git submodule update --init --recursive firmware/embassy
cd firmware/rust_bringup/stm32g4
rustup target add thumbv7em-none-eabi
rustup component add llvm-tools-preview
cargo install cargo-binutils --locked

Install probe-rs tools only if you plan to use an SWD probe. The package's Cargo configuration selects the ARM target automatically.

Firmware targets

Binary	Purpose	Interface
`twr_init`	40 Hz two-way-ranging initiator	DWM3000 + USB CDC
`twr_resp`	Ranging responder, calibration, distance stream	DWM3000 + USB CDC
`tdoa_anchor`	Configurable location anchor	UWB; configured by browser before flashing
`tdoa_tag`	Onboard 2D/3D position solver	UWB + USB CDC
`can_tx`	Classical CAN request / echo test	FDCAN2 at 500 kbit/s
`can_rx`	Classical CAN echo peer	FDCAN2 at 500 kbit/s
`can_fd_tx`	64-byte CAN FD load generator	1 Mbit/s nominal, 2 Mbit/s data
`can_fd_rx`	CAN FD sequence, loss, and throughput receiver	1 Mbit/s nominal, 2 Mbit/s data

Build without hardware

cargo check --release --bin twr_init
cargo check --release --bin twr_resp
cargo check --release --bin tdoa_anchor --bin tdoa_tag
cargo check --release --bin can_tx --bin can_rx
cargo check --release --bin can_fd_tx --bin can_fd_rx

Build a distance binary for DFU

mkdir -p out
cargo objcopy --release --bin twr_init -- -O binary out/twr_init.bin
cargo objcopy --release --bin twr_resp -- -O binary out/twr_resp.bin

These commands produce flat binaries without touching the website's distributed images. Pass your binary's absolute path to the DFU script as its second argument. Location images need the surveyed configuration described in the Location quickstart; an unpatched build does not contain your installation's survey.

Flash and attach RTT

Connect a compatible SWD probe to the 10-pin Cortex Debug header. The package runner is already configured for STM32G474CC.

DEFMT_LOG=info cargo run --release --bin can_tx

probe-rs erases and programs the image, resets the target, and displays defmt RTT output. For release role images and no local toolchain, use the browser DFU console.

Clocking assumptions

The supplied TWR and Location roles use the 8 MHz HSE with an 8 / 2 × 72 / 2 = 144 MHz system clock. The CAN examples use an 8 / 2 × 85 / 2 = 170 MHz system clock. CAN FD routes FDCAN from PCLK1. Do not copy one target's bus timing into another clock configuration.

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