Sending via Uart

[kagislason]

Hi, I need to be able to communicate between two boards via UART. I had a look at the example from Ole provided here: devzone.nordicsemi.com/.../ as well as other references here on the Dev zone and code examples in the SDK.

I am running the PCA10001 and also tested it on the N5 chip from Dynastream. The chip is using SDK v6.1 and SD s110 v7.

I need to use hardware flowcontrol and to simplify things I am currently testing it against a PC. Using Ole's code and importing it into a clean IAR project and running it on the PCA10001 the software goes into the app_error_handler after trying to run app_uart_put for the second time, the reason is a NRF_ERROR_NO_MEM error as the current state is not UART_READY. This happens for both HFC on/off.

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

Here is a copy of the app_uart_put function from app_uart.c

uint32_t app_uart_put(uint8_t byte){
    uint32_t err_code = NRF_SUCCESS;

    if (m_current_state != UART_READY)
    {
      err_code = NRF_ERROR_NO_MEM;
    }
    else
    {
      m_tx_byte = byte;
      on_uart_event(ON_UART_PUT);
    }

    return err_code;
}

By adding something like this into the app_uart_put function the problem is solved but I would rather not want to change the SDK. Could also put a fixed delay into the send function but that is an even worse hack in my opinion.

while (m_current_state != UART_READY)
{
    // Wait until uart is ready again
}

Am I using the framework incorrectly or can someone suggest a cleaner solution for this issue, the best thing would be to be able to use the app_uart library from the SDK without modification for future releases.

Thanks!

[kagislason]

Hi, in the end these chips will be on the same PCB. Currently testing this with a UB232R module to the PC, I am also monitoring the traffic using a logical analyser and the data output is as expected.

My headache comes from the way the board sends the data, it seems like the channel is clogging up when trying to send the characters too fast. I have been able to temporarily fix this issue by putting a 20us delay between sending of each character or simply spinning an empty loop until the UART is ready again.