NRF51 Uart Overrun

[Epimeth]

Hi,

I use a GPS Modul to send data via uart to the NRF 51 and then I send the string via SPI and fatfs to the SD CArd.

I see the LED4 blinking and during the debugging I can see the Uart has an overrun event. The Uart has no flow control and a baud rate from 9600.

The overrun is calling during the fatfs. So I expect losing data by writing to the SD CArd, but all data is written without any failure.

I use  normal libary, no softdevice and calling the fatfs from the main loop,

What means the LED 4, if it blinking and why i have an uart overrun event but nothing happen with the data?

[Turbo J]

It may be hard to spot with the naked eye, but you should get at least a failed checksum.

In case your code silently drops NMEA sentences with a wrong check sum, the result will look and also likely work quite acceptable.

Note: The reason you get UART overruns is that the SD card can take quite some time to write a sector. Expected worst case timing is in the 300ms to 1second range, and *much* longer if the card was badly fragmented.

[Epimeth]

You can see the behaviour in the example fatfs sdk 12.3, too.

The blinking LED 4 comes from this piece of code app_sdcard.c

__STATIC_INLINE void sdc_spi_transfer(uint8_t const * const p_txb,
                                      uint8_t tx_len,
                                      uint8_t * const p_rxb,
                                      uint8_t rx_len)
{
    SDC_CS_ASSERT();
    ret_code_t err_code = nrf_drv_spi_transfer(&m_spi, p_txb, tx_len, p_rxb, rx_len);
    APP_ERROR_CHECK(err_code);
}

with SD_CS_ASSERT() you call

nrf_gpio_port_out_clear(reg, 1UL << pin_number);

from nrf_gpio.h

It is possible to call nrf_drv_spi_tansfer and return back to the main.c without waiting? maybe with a spi event handler? Because i think it is running in blocking mode.