Hello,
I have a problem with my SAM7S256.
I am using one UART Port to communicate with my Software. It is interrupt controlled.

Now I am trying to send debug information through the other UART Interface.
This is not interrupt controlled.

Inside the ISR I have a state machine, that jumps based on the received bytes. Message format is ESC STX MSG.... CRC CRC ESC ETX.

I send current state and received byte out through the debug interface.
I would expect to receive.

1. IDLE ESC
2. PRE_RUNNING - STX
3. RUNNING - MSG ...
4. RUNNING - ESC
5. ESC_IN_MSG - ETX

But I only receive
IDLE - ETX

The state machine stays at IDLE state all the time.
Without the debugging the state machine jumps through all states.

Looks like the receiver buffers are overwritten faster than the interrupt can check for the content.

Is there any way that I can deal with this? I would guess flow control could fix my problem, but sadly CTS and RTS are not available on my development board.

Regards

Buffer the debug telemetry data in a software FIFO rather than sending it directly to the DBGU, and check the empty flag and stuff a byte out on the regular USART ISR. OR you could check/send bytes from the debug FIFO buffer in a foreground loop.

Absent CTS/RTS, you could always implement a software XON/XOFF type protocol for flow control.