nRF52 - SPIM - read buffer empty

Hi,

I have a problem with my SPIM read buffer. As you can see below, my SPI device received bytes correctly and answer correctly

image description

My code is based on SPI example SDK 12.1.

SPI initialisation

void SPI_init(nrf_drv_spi_t* spi_inst, uint32_t pin_ss, nrf_drv_spi_mode_t mode, nrf_drv_spi_frequency_t freq)
{
	nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
    spi_config.ss_pin   	= pin_ss;
    spi_config.miso_pin 	= MISO_PIN;
    spi_config.mosi_pin 	= MOSI_PIN;
    spi_config.sck_pin  	= SCLK_PIN;
	spi_config.frequency  	= freq;
	spi_config.mode		  	= mode;
    APP_ERROR_CHECK(nrf_drv_spi_init(spi_inst, &spi_config, spi_event_handler));
}

SPI default config

#define NRF_DRV_SPI_DEFAULT_CONFIG                           \
{                                                            \
    .sck_pin      = NRF_DRV_SPI_PIN_NOT_USED,                \
    .mosi_pin     = NRF_DRV_SPI_PIN_NOT_USED,                \
    .miso_pin     = NRF_DRV_SPI_PIN_NOT_USED,                \
    .ss_pin       = NRF_DRV_SPI_PIN_NOT_USED,                \
    .irq_priority = SPI_DEFAULT_CONFIG_IRQ_PRIORITY,         \
    .orc          = 0xFF,                                    \
    .frequency    = NRF_DRV_SPI_FREQ_4M,                     \
    .mode         = NRF_DRV_SPI_MODE_0,                      \
    .bit_order    = NRF_DRV_SPI_BIT_ORDER_MSB_FIRST,         \
}

SPI read / write function

void SPI_write_read_block(nrf_drv_spi_t* inst, uint8_t* ptx, uint8_t* prx, uint8_t m_length)
{
	APP_ERROR_CHECK(nrf_drv_spi_transfer(inst, ptx, m_length, prx, m_length));

	while (!spi_xfer_done)
    {
	        __WFE();
    }
	spi_xfer_done = false;
}

SPI read / write used

static uint16_t POT_read(TAD5144* ad, uint16_t reg)
{
	ad->tx_dat[0] = HI_UINT16(reg);
	ad->tx_dat[1] = LO_UINT16(reg);
	SPI_write_read_block(ad->inst_spi, ad->tx_dat, NULL, 2);
	SPI_write_read_block(ad->inst_spi, NULL, ad->rx_dat, 2);
	return BUILD_UINT16(ad->rx_dat[1], ad->rx_dat[0]); 
}

Questions

  • On SPI MISO, my data is correct, what kind of problem could be occured that MISO pin will not copy the data through easyDMA on buffer (RXD.PTR correctly initialized)
  • What I doing wrong ?
  • Something isn't correclty configured ?

SPIM0 register configuration image description

  • Don't know if this is the root cause of your problem, but you should not pass tx_buffer or rx_buffer as NULL and the length as non-zero. You can see that the nrf_drv_spi_xfer(..) function checks for this at the start of the function (the code will not assert unless NRF_ASSERT_PRESENT is defined):

    ASSERT(p_xfer_desc->p_tx_buffer != NULL || p_xfer_desc->tx_length == 0);
    ASSERT(p_xfer_desc->p_rx_buffer != NULL || p_xfer_desc->rx_length == 0);
    

    (the assert will trigger if the input is zero).