nrf52832 UART send multiple bytes

[JacksonLau]

Hi all,

    I am trying to send a command to the sensor so that the sensor will response with sending something back for acknowledgement, via UART.

    Let say, I want to send a command "SEND" to sensor, and the sensor will send its data back. However, I don't know how to modify the example code in 

    nRF5_SDK_14.2.0_17b948a\examples\peripheral\uart

    so that the code are fetching the FIFO when the '\n' is met, instead of response in every character. Right now the example is doing this for single character.

    I am not sure how to change from the example to achieve, it seems rx/tx are having independent fifo buffer, how they operate and connected?

    m_rx_fifo, m_tx_fifo

    tx_buffer[], rx_buffer[]

    nrf_drv_uart_rx(), nrf_drv_uart_tx()

    app_uart_get(), app_uart_put()

Please share your thoughts if you have any idea. Thanks

[Bastien Reynard]

No you shouldn't worry about it.

You can modify my first exemple to transmit "SEND" in sendAction(), and modify the handler to process the 2 bytes response with a counter or somthing like that. I think you'll be fine with the default fifo buffer size.

const char * send_cmd = "SEND";
char rsp[2];
uint8_t cmdIndex = 0;
...
void sendAction()
{
    uint8_t i;
    for(i = 0; i < sizeof(send_cmd); i++)
    {
        while (app_uart_put(send_cmd[i]) != NRF_SUCCESS);
    }
}
void uart_handle(app_uart_evt_t * p_event)
{
    ...
    else if (p_event->evt_type == APP_UART_DATA_READY)
    {
        
        while (app_uart_get(&cr) != NRF_SUCCESS);
        rsp[cmdIndex++] =  cr;
 
        if(cmdIndex == 2)
        {
            printf("Sensor Value : 0x%02X%02x\r\n", rsp[0],rsp[1]);
            
            cmdIndex = 0;
        }
    }
}

[JacksonLau]

May I ask why I can get correct response from sensor when I input command "SEND" on PuTTY but no response by using sendAction()?

If I connect UART to nothing, the command is correctly shown on PuTTY. It means the sendAction() has no problem.

int main(void) {
    ...
    while (true)
    {
    	sendAction();
		nrf_delay_ms(500);
		app_uart_flush();
	}
}

But when I connect the uart serial communication betweem nrf and sensor, there is no response unless I input command by keyboard, and then the console shows temperature value.

[Bastien Reynard]

What sensor are you using? Have you tried with 

const char * send_cmd = "SEND\n";

Also check you have the right UART configuration (baudrate, flow control, parity). The best would be to use a logic analyser to see what happens.