Unable to interface nrf51822 with LIS3DH (accelerometer) using SPI being nrf as master

[Agam]

Hi, 

I tried interfacing LIS3Dh using SPI, I used the SPI example to start with, when I didn't get the desired result, I look numerous question on the forum and tried to modify the code but it does not seem to be working.

I am simply trying to read WHO_AM_I register/or any other register, I am getting FF always, 

the sensor is embedded on PCB with following configurations: 

Configurations:

LIS3DH	nrf 51822 pin	sdk_config.h
SCK	9	SPI_SCK_PIN 9
SDI	10	SPI_MOSI_PIN 10
CS	12	SPI_SS_PIN 12
SDO	7	SPI_MISO_PIN 11

Below code is trying to read who_am_i ( 0x0F) 

#define SPI_INSTANCE  0 /**< SPI instance index. */
static const nrf_drv_spi_t spi = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE);  /**< SPI instance. */
static volatile bool spi_xfer_done;  /**< Flag used to indicate that SPI instance completed the transfer. */

#define TEST_STRING "Nordic"
static uint8_t       m_tx_buf[]={0x0F};           /**< TX buffer. */
static uint8_t       m_rx_buf[]={0x00, 0x00,0x00, 0x00,0x00};    /**< RX buffer. */
//static const uint8_t m_length = sizeof(m_rx_buf);        /**< Transfer length. */

/**
 * @brief SPI user event handler.
 * @param event
 */
void spi_event_handler(nrf_drv_spi_evt_t const * p_event)
{
    spi_xfer_done = true;
    SEGGER_RTT_printf(0,"Transfer completed.\r\n");
    if (1 != 0)
    {
        SEGGER_RTT_printf(0," Received: \r\n");
        NRF_LOG_HEXDUMP_INFO(m_rx_buf, strlen((const char *)m_rx_buf));
        SEGGER_RTT_printf(0, "value: %u \r\n", *m_rx_buf);
        bsp_board_led_invert(BSP_BOARD_LED_1);
    }
}

int main(void)
{
    bsp_board_leds_init();

    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));

    SEGGER_RTT_printf(0,"SPI example\r\n");

   nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
	spi_config.ss_pin   = SPI_SS_PIN;
	spi_config.miso_pin = SPI_MISO_PIN;
	spi_config.mosi_pin = SPI_MOSI_PIN;
	spi_config.sck_pin  = SPI_SCK_PIN;
	spi_config.frequency= NRF_DRV_SPI_FREQ_8M;
	spi_config.mode= NRF_DRV_SPI_MODE_2;
        
	APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, spi_event_handler));
        
       
        uint8_t sizerx = 2;
        spi_xfer_done = false;
        
        APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, 1, m_rx_buf, sizerx));
        while (!spi_xfer_done){
	  __WFE();
        }

        if(sizerx!=0)
        {
            SEGGER_RTT_printf(0,"Received[0]: %x %x %x %x %x \n\r",m_rx_buf[0],m_rx_buf[1],m_rx_buf[2],m_rx_buf[3],m_rx_buf[4]);
        }else{
            SEGGER_RTT_printf(0,"no value return from \r\n");
        }
      
      SEGGER_RTT_printf(0,"miso-> %u \r\n", nrf_gpio_pin_out_read(11));
      SEGGER_RTT_printf(0,"mosi-> %u \r\n", nrf_gpio_pin_out_read(10));
      SEGGER_RTT_printf(0,"ss-> %u \r\n", nrf_gpio_pin_out_read(12));
                     
}

log output ( in every case I am getting FF value in rx_buff ) 

SDK Used: 12.2

using JLink to transfer the via SWO

I have tried with different modes and frequencies also but no luck. 

Please help.

[hmolesworth]

You tried modes 1,2,3 but did you try mode 0? I use mode 0 with the similar part. Maybe post your code again is case we can spot something ..

[RenatoMorelli]

Sorry, my bad. I did try mode 0, which is the default one.

I slightly modified the SPI example in SDK 14.2, here how it looks like.

0x0F is the WHO_AM_I register, and I tried too 0X8F (bit 7 high for read operation).

I really appreciate your help, thanks hmolesworth. There are a few other threads about this same problem here in the devzone.

#include "nrf_drv_spi.h"
#include "app_util_platform.h"
#include "nrf_gpio.h"
#include "nrf_delay.h"
#include "boards.h"
#include "app_error.h"
#include <string.h>
#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"

#include "nrf_gpio.h"

#define SPI_INSTANCE  0 /**< SPI instance index. */
static const nrf_drv_spi_t spi = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE);  /**< SPI instance. */
static volatile bool spi_xfer_done;  /**< Flag used to indicate that SPI instance completed the transfer. */

// according to sdk_config.h
//SPI0_ENABLED 1
//SPI0_USE_EASY_DMA 1
//SPI_SCK_PIN 3
//SPI_MISO_PIN 28
//SPI_MOSI_PIN 4
//SPI_SS_PIN 29

//#define TEST_STRING "Nordic"
static uint8_t       m_tx_buf[] = {0x0F,0x00};           /**< TX buffer. */
static uint8_t       m_rx_buf[] = {0x00,0x00};    /**< RX buffer. */
static const uint8_t m_length = sizeof(m_tx_buf);        /**< Transfer length. */

/**
 * @brief SPI user event handler.
 * @param event
 */
void spi_event_handler(nrf_drv_spi_evt_t const * p_event,
                       void *                    p_context)
{
    spi_xfer_done = true;
    NRF_LOG_INFO("Transfer completed.");
    if (m_rx_buf[0] != 0)
    {
        NRF_LOG_INFO(" Received:");
        NRF_LOG_HEXDUMP_INFO(m_rx_buf, strlen((const char *)m_rx_buf));
    }
}

int main(void)
{
    bsp_board_leds_init();

    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();
    
    NRF_LOG_INFO("SPI example.");

    nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
    spi_config.ss_pin    = SPI_SS_PIN;
    spi_config.miso_pin  = SPI_MISO_PIN;
    spi_config.mosi_pin  = SPI_MOSI_PIN;
    spi_config.sck_pin   = SPI_SCK_PIN;
    spi_config.frequency = NRF_SPI_FREQ_125K;
    APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, spi_event_handler, NULL));

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

        bsp_board_led_invert(BSP_BOARD_LED_0);
        
        APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, 2, m_rx_buf, 2));

        while (!spi_xfer_done)
        {
            __WFE();
        }

        NRF_LOG_FLUSH();

        bsp_board_led_invert(BSP_BOARD_LED_0);
        nrf_delay_ms(1000);
    }
}

[hmolesworth]

Ah-Ha! Try reading .. use 0x8F not 0x0F .. similar to this - or did you try that I now notice above

    uint8_t tx_buf[] = {0x80|LIS2DH12_WHO_AM_I, 0xFF};

[RenatoMorelli]

I tried this, not working :/

I appealed to the oscilloscope and this is my SPI bitbang that works

Blue is the clock and yellow is the mosi of 0x8f (read whoami)

Blue is the clock and yellow is the chip select

------

Now the part that doesn't work, from the nordic sdk api call to spi.

Please note that this is on MODE 0.

   

nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
spi_config.ss_pin    = SPI_SS_PIN;
spi_config.miso_pin  = SPI_MISO_PIN;
spi_config.mosi_pin  = SPI_MOSI_PIN;
spi_config.sck_pin   = SPI_SCK_PIN;
spi_config.frequency = NRF_SPI_FREQ_125K;
spi_config.bit_order = NRF_DRV_SPI_BIT_ORDER_MSB_FIRST;
spi_config.mode      = NRF_DRV_SPI_MODE_0; 

Blue is the clock and yellow is the mosi of 0x8f (read whoami)

Blue is clock and yellow is the chip select

Blue is the clock and yellow is the mosi of {0x8f,0xff} (read whoami), like hmolesworth suggested