Acquiring GPS data through UART on a polling basis.

RE: Acquiring GPS data through UART on a polling basis.

sprasad — Tue, 13 Mar 2018 16:19:04 GMT

Got it working by using NRF_UART0->TASKS_STARTRX = 1 while receiving the data and then

NRF_UART0->TASKS_STOPRX = 1 and app_uart_flush() in the error handler to ignore RX overrun errors.

RE: Acquiring GPS data through UART on a polling basis.

sprasad — Mon, 12 Mar 2018 16:04:41 GMT

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?

RE: Acquiring GPS data through UART on a polling basis.

Martin Lesund — Mon, 12 Mar 2018 15:04:21 GMT

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. "

RE: Acquiring GPS data through UART on a polling basis.

sprasad — Fri, 09 Mar 2018 16:42:17 GMT

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?

RE: Acquiring GPS data through UART on a polling basis.

Martin Lesund — Fri, 09 Mar 2018 14:58:26 GMT

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.

RE: Acquiring GPS data through UART on a polling basis.

sprasad — Fri, 09 Mar 2018 12:55:36 GMT

Hello Martin,

I'm using GPS Module EM - 506.

For my application, I only need the latitude and longitude information. So, sending AT commands and receiving the data would make it complicated. Anyhow, upon connection, GPS module sends out the data as strings with a specific format. All I have to do is parse those strings and extract Latitude/ Longitude information from them.

I just want to be able to read the rx buffer of uart at will and parse the data when needed. During other times, I don't care what data in arriving on the UART port.

I would like to perform something like this

// Other functions running
// Like saadc, ble advertising

if (trigger_condition) 
{
    string = read_data_coming_from_GPS_module();
    parse_string();
}

Basically. I want to poll the UART module for data take whatever GPS module has transmitted.

I'm also curious as to why would the data transmission stop on adding that nrf_delay_ms(1000) !!

RE: Acquiring GPS data through UART on a polling basis.

Martin Lesund — Fri, 09 Mar 2018 12:29:27 GMT

Hello Sharada,

What type GPS are you using?

Usually you can send a command to to the GPS module and get the data when you ask for it.