Questions about spi read and write function mapping

[June6]

I'm having trouble driving the BMI088 with the official driver of Bosch BMI088 (link to this driver) in the ble_app_uart routine. I never get the chip ID. Bosch BMI088 official driver link address: https://github.com/BoschSensortec/BMI08x-Sensor-API . The spi read and write functions are encapsulated into the following two APIs: 

int8_t user_spi_write(uint8_t cs_pin, uint8_t reg_addr, uint8_t *data, uint16_t len);

int8_t user_spi_read(uint8_t cs_pin, uint8_t reg_addr, uint8_t *data, uint16_t len);

So How can I map these two APIs into Nordic operation functions？ 

  

And The automatic selection between [CPOL = '0' and CPHA = '0'] and [CPOL = '1' and CPHA = '1'] is controlled based on the value of SCK after a falling edge of CSB (1 or 2). What SPI mode should I configure？

[hmolesworth]

The read function shown seems to be doing a write since the LS bit is '0':

int8_t user_spi_read(uint8_t cs_pin, uint8_t reg_addr, uint8_t *data, uint16_t len)
{
    nrf_gpio_pin_clear(cs_pin);
    nrf_delay_us(1);
    if(len<=255)
    {
        uint8_t m_tx_buf[1] = {0};

I would expect setting the LS bit to '1' would perform a read, but that is either MSB first or LS Bit first, not sure which for this part:

int8_t user_spi_read(uint8_t cs_pin, uint8_t reg_addr, uint8_t *data, uint16_t len)
{
    nrf_gpio_pin_clear(cs_pin);
    nrf_delay_us(1);
    if(len<=255)
    {
        uint8_t m_tx_buf[1] = {0x01}; // if MS Bit first
        uint8_t m_tx_buf[1] = {0x80}; // if LS Bit first

It would help if you show both initialisation code (use SPI Mode 0) and detail pin connections as this part is not a simple SPI part (eg accelerometer has to be changed from I2C to SPI).

[haakonsh]

Sorry for the long wait.

The read function should look like this:

int8_t user_spi_read(uint8_t cs_pin, uint8_t reg_addr, uint8_t *data, uint16_t len)
{
    nrfx_err_t ret_code = NRFX_SUCCESS;
    nrfx_spim_xfer_desc_t my_xfer_desc = NRFX_SPIM_XFER_RX(&data, (len + 1));
    
    uint8_t m_tx_buf[MAX_LENGTH];   // create buffer
    memset(&m_tx_buf, 0, sizeof(m_tx_buf)); //clear buffer
    
    m_tx_buf[0] = (1 << 0) | (reg_addr << 1);
    
    /* Configure the Chip Select pin, SPIM3 supports HW controlled CS pin*/
    NRF_SPIM3->PSEL.CSN = cs_pin;
    
    ret_code = nrfx_spim_xfer(&my_spim_instance, my_xfer_desc, flags);
    APP_ERROR_CHECK(ret_code);
    
    return;
}

[June6]

Although I have solved the problem myself, thank you for replying to me!

[pradeepyadav]

Hi june6,

i got the same issue , i am trying to interface spi nor flash with nRF52840 but not able to read the device ID?

[June6]

Hi,

I use Bosch driver, there is no problem at all. Here is my SPI configuration:

#define NRF_DRV_SPI_BMI088_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_8M,                     \
    .mode         = NRF_DRV_SPI_MODE_0,                      \
    .bit_order    = NRF_DRV_SPI_BIT_ORDER_MSB_FIRST,         \
}

#define SPI_INSTANCE_0                  0                                           /**< SPI instance index. */

static const nrf_drv_spi_t spi_0_bmi088 = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE_0);     /**< SPI instance. */


nrf_drv_spi_config_t spi_bmi088_config = NRF_DRV_SPI_BMI088_DEFAULT_CONFIG;

nrf_gpio_cfg_output(MCU_GPIO_BMI088_CSB1);
nrf_gpio_cfg_output(MCU_GPIO_BMI088_CSB2);
nrf_gpio_pin_set(MCU_GPIO_BMI088_CSB1);
nrf_gpio_pin_set(MCU_GPIO_BMI088_CSB2);

spi_bmi088_config.ss_pin   = NRF_DRV_SPI_PIN_NOT_USED;
spi_bmi088_config.miso_pin = SPI_BMI088_MISO_PIN;
spi_bmi088_config.mosi_pin = SPI_BMI088_MOSI_PIN;
spi_bmi088_config.sck_pin  = SPI_BMI088_SCK_PIN;
APP_ERROR_CHECK(nrf_drv_spi_init(&spi_0_bmi088, &spi_bmi088_config, spi_bmi088_event_handler, NULL));