A defmt target for logging over a serial port. Have a look at examples to see how to use library example-artemis or example-pi-pico. You can also try it out in a hosted environment: example-std. To parse the logs have a look at parsing logs.

static SERIAL: StaticCell<hal::uart::Uart0> = StaticCell::new();

#[entry]
fn main() -> ! {
    let mut dp = hal::pac::Peripherals::take().unwrap();
    let pins = hal::gpio::Pins::new(dp.GPIO);

    // set up serial
    let serial = hal::uart::Uart0::new(dp.UART0, pins.tx0, pins.rx0);
    defmt_serial::defmt_serial(SERIAL.init(serial));

    defmt::info!("Hello from defmt!");

    loop {
        asm::wfi();
    }
}

Remember to set the DEFMT_LOG variable when testing, e.g.:

$ cd example-std/
$ DEFMT_LOG=debug cargo run

The easiest way to parse the logs is to use socat and defmt-print together. For example:

$ socat ${PORT},rawer,b${BAUDRATE} STDOUT | defmt-print -e ${ELF}

Just replace ${PORT}, ${BAUDRATE} and ${ELF} with correct values.

To install the tools on Ubuntu 22.04 run these commands:

$ apt install socat
$ cargo install defmt-print

Note that on Mac OS it seems that socat is broken for this purpose. Use stty and cat in stead:

$ (stty speed 115200 >/dev/null && cat) </dev/cu.usbserial-10 | defmt-print -e $(ELF)