freeRTOS software timer for ESP32 UART timeout

blavo1 wrote on Sunday, March 05, 2017:

I’m looking for some example code the shows how to set up a freeRTOS software timer. Basically I’m trying to recieve a fixed packet length on the UART of three consecutive bytes. I created a task that recieves the characters from the UART and builds the 3 byte packet and sends the completed packet via message queue to another task.

Within the task that builds the three byte packet, I’d like to incorporate a timer that will track elapsed time and flag an error if the three bytes aren’t recieved within a specified time.

So the process would be this;

Uart character recieved;
get initial timer value, start timer ;
wait for second byte; check timer elapsed;
wait for third byte; check timer elapsed;
if three bytes received within the specified time, message off packet to other task with error flag clear
else if timer elapsed set error flag and message off to other task with packet array clear
clear intial timer value, stop timer

Any help is greatly appreciated.

rtel wrote on Sunday, March 05, 2017:

How is the task waiting for the bytes? If it is blocking on a
queue/event group/semaphore/direct notification, then you can use the
timeout in the blocking API call. If the timeout times out then you
know it took too long. You can check the RTOS tick count at the start
and between bytes to make any adjustments (xTaskGetTickCount()) or even
use the vTaskSetTimeout() function.

blavo1 wrote on Monday, March 06, 2017:

These are all good ideas and I like the idea of using the timeout in the queue where it’s blocking. BTW, I am starting to find more code samples that explain the mechanics of how to do this and I think I have a pretty good idea on how to proceed. Thanks for the help.