uart 9-O-2 protocol

[nichtgedacht]

Posted on January 28, 2017 at 17:54

Is it really impossible to set the STM32 MCU UART for 9-O-2 or 9-O-1 ?

[Tesla DeLorean]

Posted on January 28, 2017 at 18:09

As stated, it is not possible. You might be able to fake such output using SPI

Not that those are prolifically used, this sounds like a pretty niche configuration based on some other hardware in that space.

The USART can send 9 data bits, including parity and up to 2 stop bits.

[T J]

Posted on January 28, 2017 at 23:45

You can bitbash using a port pin. using a timer interrupt.

easy enough...

what baud rate ?

if the baud rate is high, then you will have to use the ouputCompare function of a timer pin to set the pin in advance of the bit boundary.

ie.

initialise timer interrupt for 1 bit time, set the pin high and set the pin to toggle on OC event. this will send the start bit at the instant of the timer interrupt.

then set the next transition to be high or low, and reset the OC trigger.

but I don't think you could go above 115200. without using 50% of the cpu time.