RE: Sending a single Byte over SPI

Yasser — Sat, 20 Jul 2019 01:53:50 GMT

Hi Eric,

I am using SDK 15. Need to send a single byte - address of the register. Nothing to read in the first transfer. Then send another byte "0" to read the data. I am using your approach of setting 0 for rx buffer len. But doesn't work. Did you change the driver as suggested by

Offline knisbet over 3 years ago

This method did not work for me using SDK11. Nordic provided the following fix. The SDK drivers is not designed for this workaround.

The stop event was not handled. In srf_drv_spi.c replace irq_handler_spim at line 557 with the below

https://devzone.nordicsemi.com/f/nordic-q-a/11438/problems-implementing-workaround-to-get-nrf52-to-send-an-octet-one-byte-through-spi/43155?focus=true

This is my code:

int main(void)
{
    bsp_board_init(BSP_INIT_LEDS);

    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
    spi_config.ss_pin   = NRF_DRV_SPI_PIN_NOT_USED;
    spi_config.miso_pin = 7;
    spi_config.mosi_pin = 15;
    spi_config.sck_pin  = 12;
    APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, spi_event_handler, NULL));

    SEGGER_RTT_printf(0,"SPI example started.");
    

    while (1)
    {
        // Reset rx buffer and transfer done flag
        memset(m_rx_buf, 0, 1);
        spi_xfer_done = false;

        ret_code_t err_code;


        m_tx_buf = 0xAE;

        nrf_gpio_pin_clear(16);
        err_code = nrf_drv_spi_transfer(&spi, m_tx_buf, 1, m_rx_buf, 0);

        m_tx_buf = 0x00;
        err_code = nrf_drv_spi_transfer(&spi, m_tx_buf, 1, m_rx_buf, 1);

        APP_ERROR_CHECK(err_code);

        nrf_gpio_pin_set(16);
        SEGGER_RTT_printf(0,"SPI 1.");
        while (!spi_xfer_done)
        {
            __WFE();
        }

        SEGGER_RTT_printf(0,"SPI 2.");    
        SEGGER_RTT_printf(0, "%d Should be = 51\n", m_rx_buf);
        NRF_LOG_FLUSH();

        bsp_board_led_invert(BSP_BOARD_LED_0);
        nrf_delay_ms(200);
    }
}

I am getting stuck in while (!spi_xfer_done)
{
__WFE();
}

I am trying to use SPI with ADS1293 with nRF52832. Here's arduino code that works:

byte readRegister(byte reg) {
  byte data;
  reg |= 1 << 7;
  digitalWrite(pin_SS, LOW);
  SPI.transfer(reg);
  data = SPI.transfer(0);
  digitalWrite(pin_SS, HIGH);
  return data;
}

RE: Sending a single Byte over SPI

Eric — Thu, 13 Dec 2018 21:49:26 GMT

The best solution I found was given by joe.ker:

devzone.nordicsemi.com/.../43155

I can confirm this works in SDK15.2 (Sept-2018).

if (len == 1)
{
    err_code = nrf_drv_spi_transfer(&m_spi_master, m_buffer_tx_spi, len, m_buffer_rx_spi, 0);
}
else
{
    err_code = nrf_drv_spi_transfer(&m_spi_master, m_buffer_tx_spi, len, m_buffer_rx_spi, len);
}

RE: Sending a single Byte over SPI

Martin Lesund — Fri, 17 Aug 2018 13:45:05 GMT

Hi Scott,

When working with SPI I highly recommend that you use a logic analyzer (ex. saleae) to check what is going on in the different signal lines.

When it comes to the errata 58 here is a thread describing how to use it.