How to properly switch between UART pins and baud rates with nRF52 (UARTE)

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

bjorn-spockeli — Mon, 01 Mar 2021 06:41:17 GMT

RixtronixLAB: If you take a look at the nrfx_uart_init function in the UART Driver API, then you can see that you need to provide a UART instance as a parameter, which points to the UART peripheral you want to use.

You create an instance with the NRFX_UART_INSTANCE macro and you can see the available instances for the nRF52840 under nRF52840 Product Specification > Core components > Memory >Instantiation.

So if you want to use UARTE0 you pass 0 as the ID to the NRFX_UART_INSTANCE macro, if you want to use UARTE1, then you pass 1 to the NRFX_UART_INSTANCE macro.

Best regards

Bjørn

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

RixtronixLAB — Tue, 26 Jan 2021 22:17:23 GMT

How do you initialize 2 UARTs ?

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

bjorn-spockeli — Tue, 18 Apr 2017 11:06:14 GMT

Happy to help :)

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

Poonam — Tue, 18 Apr 2017 10:56:20 GMT

yes, i m using gsm module. and this works . Thank u.

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

bjorn-spockeli — Tue, 18 Apr 2017 07:40:20 GMT

Are you using a GPS module that outputs NMEA strings? If that is the case, then you can look for the character, i.e. "\n" which terminates every NMEA sentence to separate them from each other. You can also look for the "$" at the start of each sentence.

void uart_event_handle(app_uart_evt_t * p_event)
{
    static uint8_t data_array[256];
    static uint8_t index = 0;
    uint32_t       err_code;

    switch (p_event->evt_type)
    {
        case APP_UART_DATA_READY:
            UNUSED_VARIABLE(app_uart_get(&data_array[index]));
            index++;
       
            if ((data_array[index - 1] == '\n'))
            {
                \\ parse NMEA sentence here.
            }

                index = 0;
            }
            break;
}

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

Poonam — Tue, 18 Apr 2017 07:23:39 GMT

@Bjørn Spockeli : no i don,t have any provision for hardware flow control.

void uart_event_handler(nrf_drv_uart_event_t * p_event)
{
	if ( p_event ->type == NRF_DRV_UART_EVT_RX_DONE)
		{
			if(rx_index < 256)
			{
				app_uart_get(&gps_rx_buf[rx_index]);
				rx_index++;
			}
			else if (rx_index >= 256)
			{
				rx_index =0;
				app_uart_get(&gps_rx_buf[rx_index]);
				rx_index++;
			}
		}
}

is it fine ,if i used it like this?

how to stop reception to avoid overlapping of data ?

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

bjorn-spockeli — Tue, 18 Apr 2017 07:10:10 GMT

I recommend setting the RX buffer size equal to the largest string that you expect to receive. No, once 256 bytes has been received and you have not retrieved the data using app_uart_get, then you will get the APP_UART_FIFO_ERROR event, indicating that the FIFO is full. Does the device you're communicating with over UART support Hardware Flow Control? If yes, then the app_uart module will make sure that no that is sent if the buffer is full.

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

Poonam — Tue, 18 Apr 2017 06:34:59 GMT

thank you @Bjørn Spockeli , i have one more question..i kept Rx buffer size 256 and i am receiving continuous data on UART . what if my data exceeds 256 bytes will it roll over automatically? how can i disable reception when desired string is received?

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

bjorn-spockeli — Tue, 18 Apr 2017 06:16:14 GMT

@poonam: Yes, that should be possible, but you will have to use the app_uart_init function directly and not the APP_UART_FIFO_INIT() macro when switching between two instances.

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

Poonam — Sat, 15 Apr 2017 11:32:45 GMT

I am also using nRf52832 DK , Can i use 2 uart instance using APP_UART_FIFO_INIT() and app_uart_close() ; and then re-initialize the instance with the new configuration..........?

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

Anders Strand — Tue, 07 Feb 2017 10:32:37 GMT

Thank you. Your assumption of me using the nRF52832 is correct :)

RE: How to properly switch between UART pins and baud rates with nRF52 (UARTE)

bjorn-spockeli — Tue, 07 Feb 2017 10:19:57 GMT

Hi Anders,

I am assuming that you're using the nRF52832, the multi-instance support in the UART driver is a nRF52840 specific feature since it has two UARTs. This is stated in the SDK v12.2.0 Release Notes, found here.

So, if you need to change the configuration of your UART instance, you must un-initialize and then re-initialize the instance with the new configuration like you stated in your question. As far as I know the nrf_drv_uart_init and nrf_drv_uart_uninit calls are synchronous, so as soon as they have returned NRF_SUCCESS you should be able to TX/RX with the new configuration.

Best regards

Bjørn