STM32F411 USART RTS problem

tm3341 · ‎2015-07-17

Posted on July 17, 2015 at 13:43

Hello everyone,

I'm getting strange behaviour on my STM32F411 device.

I use USART 1 with hardware flow control, with pins:

TX: PB6,

RX: PB7

RTS: PA11

CTS: PA12

The problem I have, is that when device wake up from STOP mode, RTS pin does not work properly for about 10 bytes received via USART. I have image attached to clearly show behaviours of this pin.

So, before I go to STOP mode, I deinit USART, and force RTS high with GPIO pin as output to prevent my device to send me any data.

After I wakeup (on image where TX goes high), I set clock back and then initialize USART peripheral.

When my device starts with sending data, RTS pin of STM32F411 is ''shifted'' to to middle of next byte (attached on picture). In my case, I miss first 6 bytes and then RTS pin is located OK and also IRQ for USART is also OK.

Any ideas what is happening here?

This happens only if I init usart from wakeup directly.

Thanks for any help,

have a nice day.

#rts #usart #cts #stm32-stm32f4