I have a STM32L4xx series microcontroller. My goal is to use RTO in USART to issue a timeout, from the time a read was attempted (not only from the last stop bit). This is needed as its possible for nothing to be received. How do I acheive this using RTO?

[David Ledger]

I've setup USART to interrupt on a timeout using:

CR2.RTOEN

CR1.RTOIE

And configured the timeout using:

RTOR.RTO

It works great, really nice feature. The RTO timeouts are always measured from the last stopbit/character received. However, I need to support a timeout even if zero characters were received. Does anybody know of a method to reset the RTO counter etc?

[KnarfB]

I doubt that RTO can be used for that. A simplistic approach would be using HAL_UART_Receive with a small timeout value (SysTick). A more sophisticated approach could start a timer and use a timer interrupt when the time is over.

[Piranha]

For "no reception" timeout typically a notification/event/semaphore wait function or other independent software/hardware timeouts are used.

[David Ledger]

I thought that might be the case. Was looking for a dependable workaround to keep timeout functionality to the peripheral itself (just seemed like more modular design).

Appreciate the responses. Shame its not possible, honestly it seems like a trivial change to the functionality (force manual triggering of a stop bit). That said, I understand that'd be a respin of silicon and thats just not going to happen :(

Does anybody know if using internal pull-ups and bitbanging a USART rx to a stopbit would work?

[waclawek.jan]

>using internal pull-ups and bitbanging a USART rx to a stopbit

Surely the connected device pulls stronger than the pull-ups. And if not, you're risking corruption of genuinely incoming data.

> Shame its not possible, honestly it seems like a trivial change to the functionality

You can start an "Idea", maybe it'll stick, at least for future devices.

Meantime, just accept the status quo, as Piranha and KnarfB said.

JW

[David Ledger]

thanks!