TM4C123GH6PM: UART stops working when enabling overrun error interrupts

Not sure, but here is a thought. When you suspend the CPU you create an overrun. When you resume, both the overrun and the RX interrupts are set. When you check the status for "ui32status == UART_INT_RX" it will fail because the status is "UART_INT_RX | UART_INT_OE", so you don't read any characters from the FIFO. Since the FIFO is full, the next character received creates a new overrun and again, the interrupt routine does not read any characters from the FIFO. Your check for a RX interrupt might be better written as:

    if((ui32status & UART_INT_RX) != 0u)

Some additional suggestions. If you are using the FIFO you might want to also enable the receive timeout interrupt and check for either the FIFO level or the timeout.

    if((ui32Istatus & (UART_INT_RX | UART_INT_RT)) != 0)

Also, you might want to move the line clearing the interrupts to earlier in the service routine. Here is the note in "uart.c" above the UARTIntClear() function:

//! \note Because there is a write buffer in the Cortex-M processor, it may
//! take several clock cycles before the interrupt source is actually cleared.
//! Therefore, it is recommended that the interrupt source be cleared early in
//! the interrupt handler (as opposed to the very last action) to avoid
//! returning from the interrupt handler before the interrupt source is
//! actually cleared.  Failure to do so may result in the interrupt handler
//! being immediately reentered (because the interrupt controller still sees
//! the interrupt source asserted).

Thank you very much for your detailed reply, its very helpful. I will try your suggestions tomorrow and see if that solves my problem. The UART FIFO is disabled by the way. In terms of checking for interrupts, should I use the format you suggested to isolate the different interrupt sources, in addition to the receive interrupt? So:

if((ui32status & UART_INT_RX) != 0u) {} //receive

if((ui32status & UART_INT_TX) != 0u) {} // transmit

if((ui32status & UART_INT_OE) != 0u) {} // overrun error

etc.

Best regards,

Ksawery