NRF51 Uart Overrun

RE: NRF51 Uart Overrun

Jørgen Holmefjord — Wed, 02 May 2018 09:24:47 GMT

You should consider moving to nRF52 series. nRF52 series have EasyDMA on SPI and UART peripherals, allowing the peripherals to transmitt/receive data while CPU is busy handling other events/tasks.

RE: NRF51 Uart Overrun

Turbo J — Sun, 29 Apr 2018 11:32:38 GMT

That would require something like an RTOS, and might be too much for the limited RAM on NRF51, but YMMV.

The FATFS code is rather complex and will likely only work properly when called from main(). It also expects disk read and write calls to be blocking.

The only other way is to use a rather large UART buffer for the GPS data.

RE: NRF51 Uart Overrun

Epimeth — Fri, 27 Apr 2018 14:29:14 GMT

You can see this behaviour in the example fafts sdk12.3, too.

The Blinking LED 4 comes from this pieces 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 SDC_CS_ASSERT() you call from nrf_gpio.h

nrf_gpio_port_out_clear(reg, 1UL << pin_number);

It is possible after calling nrf_drv_spi_transfer to return back to main.c, without waiting? Maybe with a spi eventhandler?

Because i think it is running in blocking mode.

RE: NRF51 Uart Overrun

Epimeth — Fri, 27 Apr 2018 14:21:42 GMT

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.

RE: NRF51 Uart Overrun

Turbo J — Fri, 27 Apr 2018 12:03:12 GMT

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.