Sometimes only first char sent over UART using app_uart_fifo, then dead silent

[pontusarfwedson]

I control a module over UART using app_uart_fifo. This module is controlled from nRF host by commands to perform things. This generally works fine but however, sometimes when trying to send command it only writes out first character and then everything is quiet. This is the longest command we ever use so I suspect it has something to do with buffers since only the longest cmd has this behaviour. The others always works, this one will fail about once every 50th time. All of my buffers should be big enough to handle the message (and obviously they do that ~49/50 times). My way of sending message using app_uart_fifo is standard:

void wifi_app_uart_putstring(char * s) { uint32_t err_code;

uint8_t len = strlen((char *) s);
for (uint8_t i = 0; i < len; i++)
{
    err_code = app_uart_put(s[i]);
    APP_ERROR_CHECK(err_code);
}

}

When doing so the chip should do a reboot if it encounters issues on putting the char's on UART. And in fact, the chip does this sometimes. Sometimes it prints out the "A" and then instantly reboots, which in my implementation is far more advantageous than the behaviour when it just goes silent.

Any ideas or suggestions?

Regards, Pontus

[Susheel Nuguru]

I do not think this should be the problem unless the timer interrupt callback time is like a millisecond or so. Try to change the priority of the FIFO to higher priority, see if it helps. if your app can compromise timer callback lantency little bit, then I see no problem in increasing uart priority.