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UART interrupt issue

Question asked by Volker Weber on Jul 7, 2019
Latest reply on Jul 17, 2019 by Volker Weber

I am facing a UART interrupt issue with my current setup which occurs not deterministically after a variable period of time.


My setup in detail:

  • LPC1768
  • FreeRTOS
  • 2 UARTs:
    • 1 UART incoming data with 200 Hz is copied within the ISR into a ringbuffer and processed within a task
    •  1 UART as console
  • Output over CAN


What happens (error description):
After an undefined period of time (between 30 minutes and several hours) the UART callback related to receiving data is not called anymore. As a result, it seems that no new data is avaiable as the ringbuffer head is not moved anymore. What I can see from the debugger is, that the program is still running. For data incoming with 100 Hz over UART, this issue seems not to occur.


Some things I already tried:

  • checked that the interrupt flag for receiving new data is still set
  • increased task stack sizes and ringbuffer size
  • compiled with -fstack-check to check for stack overflows
  • protected the ringbuffer with CRITICAL statements against reading and writing from the ISR and the task
  • checked the receiving data buffer: there is new data available (but the interrupt won't hit)


I am running out of ideas how to further deal with this. Any suggestions are appreciated.