Acquiring GPS data through UART on a polling basis.

[sprasad]

I'm able to successfully use peripheral/uart example to read the data from GPS module. I achieved the same by setting baud rate to 4800, and connecting rx and tx of GPS to pins 6 and 8 respectively. Currently I have the GPS data printed on my console(CoolTerm). 

While the GPS module is continuously throwing data out of UART, how can I read this GPS data from UART only at specific intervals?

Is there a way where I can perform something like this? Enable UART, Collect data, Disable Uart. Again when I need GPS data, repeat the same procedure.

I also tried to incorporate a delay in my code to check if I can finish all my other tasks and then come back to read the data. But my console shows nothing!

while (true) {
    uint8_t cr[250];
    while (app_uart_get(&cr[gps_idx]) != NRF_SUCCESS);
    while (cr[gps_idx] != '\r') {
        gps_idx++ ;
        while (app_uart_get(&cr[gps_idx]) != NRF_SUCCESS);
    }

    printf("GPS Data One line end\r");
    for (int j=0; j<=gps_idx; j++) {
        printf("%c", cr[j]);
    }
    printf("GPS Data One Line printed\r\r");
      
    gps_idx = 0;
    
    // Works fine without this delay
    nrf_delay_ms(1000);
}

[Martin Lesund]

The nrf_delay_ms(1000); stalls the CPU for 1 sec. at that point in your while loop. 

 

I would invite you to look at the GPS whitepaper and configure it to send a signal through the "Directive" line when the GPS data is ready, and connect that line to one the GPIOs to the nRF device. Then use that interupt to start reading the UART data from the GPS module.

I see that you can configure the GPS module to send data in intervals. 

 

[sprasad]

Yes, you are right that the delay stalls the CPU, but after that, the while loop should continue and it should go ahead and read further characters through the uart right? Why isn't that happening?

[Martin Lesund]

If the CPU is stalled while the GPS module is continuously sending data to the device, and you chose to "jump randomly in" to read data, that will cause problems. (UARTE documentation)

Anyway, "I would invite you to look at the GPS whitepaper and configure it to send a signal through the "Directive" line when the GPS data is ready, and connect that line to one the GPIOs to the nRF device. Then use that interupt to start reading the UART data from the GPS module.

I see that you can configure the GPS module to send data in intervals. "

[sprasad]

Hey Marthin, Thank you for your inputs. Here is my problem,

1) I don't have to rely on directive line on the GPS module because I don't want to know when the data ready, all I want to do is to read the data when I'm ready (assuming that GPS has a valid data).

2) I also do not want to receive the data at specific intervals. Again, as mentioned, I just want to read the GPS data when I need it. 

So, my thought is as follows, let the GPS continuously transmit data over UART. When I want the data, I would like to just go read the UART buffer and interpret the location. Isn't something like that possible at all?