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!

[Asbjørn]

Which version of the nRF51822 are you using. There was an increase in the UART buffers between revision 1 and revision 2 of the chip from 2 byte to 6 bytes.

nRF51822 QFAAC0 is first revision. nRF51822 QFAAG0 is second revision.

You have at least two nRF51822 or are you planning on having two different UART chips talking to each other? What's the setup you are actually looking for?

[kagislason]

The board goes to the NO_MEM error immediately after sending the first byte, because the UART_READY event has not been enabled yet. The app_uart_put(uint8_t byte); function writes the byte to the m_tx_byte buffer but there is no space for the next byte as the board has not finished writing the previous byte. I can't really see how the buffering works here and it seems like the code in the app_uart library is not working up to specification ? I understand that I am trying to push bytes to the app_uart_put function too fast but if the board has a 6 byte buffer my problem should not appear when trying to send byte number 2 ? Thanks for taking the time to follow this through, I appreciated it!