Fix stm32 uart set_config

[andresv]

• CR1 UE must be false when setting word length and parity bits.
• use type ConfigError = ConfigError instead of type ConfigError = ()
• In mod.rs there is fn configure() which uses write to set CR1. This disables RXNEIE and IDLEIE in CR1 and those must be re-enabled again. Otherwise receive does not work anymore.

TODO (done)

• What to do with fifoen, which one is correct?

embassy/embassy-stm32/src/usart/mod.rs

Lines 998 to 999 in ca27590

	#[cfg(usart_v4)]
	w.set_fifoen(true);

vs

embassy/embassy-stm32/src/usart/buffered.rs

Lines 236 to 237 in ca27590

	#[cfg(lpuart_v2)]
	w.set_fifoen(true);

Edit: usart_v4 is correct.

TEST

Tested with stm32g081 by reconfiguring baudrate, parity and stop bits.

[Dirbaio]

could you put this reg write in reconfigure instead of pasting it 3 time?

[andresv]

reconfigure is universally used for all uart flavors. For example when buffered uart is created it calls configure and then sets other registers that are needed for this driver:

embassy/embassy-stm32/src/usart/buffered.rs

Lines 233 to 241 in ca27590

	configure(r, &config, T::frequency(), T::KIND, true, true)?;
	r.cr1().modify(|w| {
	#[cfg(lpuart_v2)]
	w.set_fifoen(true);
	w.set_rxneie(true);
	w.set_idleie(true);
	});

So putting it to confgure is not a good place. I'll check if I can refactor it a little to remove copy-pasting.

[andresv]

I cleaned it up a little by removing redundant w.set_fifoen(true); which is set in configure anyway.
There isn't a good place where to put those copy pasted lines without introducing more complexity.
configure configures all the basic stuff which is used in all uart flavours and then extra configuration is done in buffered.rs which is needed for this specific impl.

I would keep it as is without adding extra stuff to basic configuration.
Although I was thinking that maybe we can remove those self.set_config functions altogether and only rely on SetConfig trait as in here.

Then all the configuration related stuff is neatly together and there is less chance that somebody forgets to update something. However then again SetConfig trait must be imported by the user which is inconvenient.

[Dirbaio]

oh okay! I had missed that, sounds good then! thanks :)

[Dirbaio]

thank you!