uart brk_det interrupt stops working after transmit, txfifo_empty causes crash

humptydumpty
Posts: 13
Joined: Thu Sep 07, 2017 10:26 am

uart brk_det interrupt stops working after transmit, txfifo_empty causes crash

Postby humptydumpty » Tue Oct 03, 2017 11:12 pm

We are using the uart brk_det interrupt to receive DMX data over UART. This appears to work reliably.

However, now we are implementing an RDM responder and must transmit as well as receive data.

We observe the following unexpected sequence of events:

1. configure uart to generate brk_det and rxfifo_full interrupts
2. the interrupts are generated and we receive messages prefaced by break.
3. load some data in tx_fifo. it is transmitted normally.
4. we continue to receive messages prefaced by break.
5. reconfigure baud rate of uart in order to send a break.
6. transmit some data
7. configure it back to original value.
8. brk_det interrupts are no longer generated. rxfifo_full interrupts continue normally.

workaround: if we reset the uart entirely with uart_param_config and uart_set_pin, then the brk_det interrupt is again generated.

Furthermore, we also notice that the processor instantly crashes when the following instruction is executed:

Code: Select all

UART_ENTER_CRITICAL(&uart_spinlock[uart_num]);
UART[uart_num]->int_clr.txfifo_empty = 1;
UART[uart_num]->conf1.txfifo_empty_thrhd = 1U;
UART[uart_num]->int_ena.txfifo_empty = 1;
UART_EXIT_CRITICAL(&uart_spinlock[uart_num]);


Has anyone ever used these interrupts successfully?

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