NRF51822 UART hangs and requires power cycle

[srijan12]

Hi,

I am making a GPS tracking system using NRF51822-QFAC. I am using 2 UARTs, one of the (external) GPRS IC and one for (external) RS485 communication.

The UART peripheral hangs after some time. I don't know if it is UART1 or UART2. As a result, both the UART do not work for a period ranging from 1 hour to 5 hours. There is an external IC that lowers NRF_SWIO (programming pin) to reset the NRF periodically every 30 minutes. But this issue persists beyond that and needs a Power Cycle.

There was a similar issue reported, but it had something to do with Segger, which I am not using. I am not using BLE or any stack. Application is built on this example location:

\nRF5_SDK_12.2.0_f012efa\examples\peripheral\uart\pca10028\blank\arm5_no_packs

We made 15 devices and the issue occurs randomly in most of them. I am logging data on an SD card (through SPI and FATFS) and in the card the data comes Zero (that is how I know UART hangs). The pattern is not periodic.

This is the UART initialization code:

define MAX_TEST_DATA_BYTES     (15U)				/**< max number of test bytes to be used for tx and rx. */
define UART_TX_BUF_SIZE 				256					/**< UART TX buffer size. */
define UART_RX_BUF_SIZE 				256					/**< UART RX buffer size. */
define MRST  								15
define HWFC            			false
define RS485_RX_PIN_NUMBER  	12
define RS485_TX_PIN_NUMBER  	11
define GPS_RX_PIN_NUMBER	  	14
define GPS_TX_PIN_NUMBER  		13
define GEN_CTS_PIN_NUMBER 		17
define GEN_RTS_PIN_NUMBER 		18

const app_uart_comm_params_t comm_params_A =
	{
			GPS_RX_PIN_NUMBER,
			GPS_TX_PIN_NUMBER,
			GEN_RTS_PIN_NUMBER,
			GEN_CTS_PIN_NUMBER,
			APP_UART_FLOW_CONTROL_DISABLED,
			false,
			UART_BAUDRATE_BAUDRATE_Baud9600
	};

APP_UART_FIFO_INIT(&comm_params_A,
										 UART_RX_BUF_SIZE,
										 UART_TX_BUF_SIZE,
										 uart_error_handle_A,
										 APP_IRQ_PRIORITY_LOW,
										 err_code_GPS);

APP_ERROR_CHECK(err_code_GPS);	

And this is snippet of how data is transmitted (the packet is generally more than 256 bytes in length):

strcpy(uploadString, "&x_no=0&x_gs=00");

for (i=0; i<strlen(uploadString); i++)
{
	app_uart_put(uploadString[i]);
}

Is there a problem with pin numbers? Or Initialization method? Or transmission method? Or should I not use app_uart library? Or should I not use FIFO?

Please suggest, as this is becoming source of data inconsistency.

[srijan12]

It happens once in couple of days, and also not on each device. It seems to be framing issue. Also feels like overflow.

As of now, the uart_error_handle_A() does nothing. What should I write into it? Probably resetting all registers, clearing all buffers and restarting UART there should work.