Stm32f303 Usart gibberish

[hdoordt]

Hi,

I'm trying to set up a serial connection using usart on the stm32f3Discovery, which has an stm32f303vc cpu on it. When sending text to it using Minicom, I get gibberish back. For instance, when typing abcdefghijklmnopqrstuvwxyz, I get yz{|}~hijklmnoxyz{|}~xyz. So, for some chatacters the value is correct, for some not. And the results are consistent.

This is my code:

#![no_std]
#![no_main]

use cortex_m_rt::entry;

use stm32f3xx_hal::prelude::*;
use stm32f3xx_hal::stm32;

#[panic_handler]
unsafe fn panic_handler(info: &core::panic::PanicInfo) -> ! {
    cortex_m_semihosting::hprintln!("ERROR! {:?}", info).unwrap();
    loop {}
}

#[entry]
fn main() -> ! {
    let peripherals = stm32f3xx_hal::stm32::Peripherals::take().unwrap();
    let mut rcc = peripherals.RCC.constrain();
    let mut flash = peripherals.FLASH.constrain();
    let clocks = rcc.cfgr.freeze(&mut flash.acr);

    let mut gpioa = peripherals.GPIOA.split(&mut rcc.ahb);

    let usart1_txd = gpioa.pa9.into_af7(&mut gpioa.moder, &mut gpioa.afrh);
    let usart1_rxd = gpioa.pa10.into_af7(&mut gpioa.moder, &mut gpioa.afrh);

    let usart1 = stm32f3xx_hal::serial::Serial::usart1(
        peripherals.USART1,
        (usart1_txd, usart1_rxd),
        9600.bps(),
        clocks,
        &mut rcc.apb2,
    );

    let (mut usart1_tx, mut usart1_rx) = usart1.split();

    loop {        
        match usart1_rx.read() {
            Ok(b) => nb::block!(usart1_tx.write(b)).unwrap(),
            Err(nb::Error::Other(_)) => {
                let usart1 = unsafe { &*stm32::USART1::ptr() };
                usart1.icr.write(|w| unsafe { w.bits(0xFF) });
            }
            _ => (),
        }
    }
}

Here's my .minirc.dfl:

pu baudrate 9600
pu bits 8
pu parity N
pu stopbits 1
pu rtscts No
pu xonxoff No

The command I use to start minicom:

$ minicom -D /dev/ttyUSB0 -b 9600 -o

Anybody know what causes this behaviour?

[vmedea]

Without anything else to go by, I'd guess the baud rate is slightly out of whack. Maybe the clocks on the stm are not exactly what rust thinks they are?

[trembel]

I don'g know how STM works, but maybe your code uses the DMA.. Then you should try b ocking also the read, or not using DMA

[lonesometraveler]

Sounds like a clock issue. I think you are using the HSI clock. Maybe using the HSE would help?

let clocks = rcc.cfgr.use_hse(8.mhz()).freeze(&mut flash.acr);

[hdoordt]

That's the solution! Thanks a bunch.