Slave select pin always low

[dkj047]

Hi 

The slave select (ss) pin during the spi communication is always low even when i make it high to release the spi bus. It looks to me that I'm not actually controlling the ss pin. 

I am using nrf52840, soft device is enabled.

My spi open code looks like following:

bool spi_open(uint8_t index, nrf_drv_spi_frequency_t freq, nrf_drv_spi_mode_t mode)
{

  if (index == SPI0)
  {
    nrf_drv_spi_config_t spi0_config = NRF_DRV_SPI_DEFAULT_CONFIG;

    spi0_config.miso_pin = SPI0_MISO_PIN;
    spi0_config.mosi_pin = SPI0_MOSI_PIN;
    spi0_config.sck_pin = SPI0_SCK_PIN;  
      
    spi0_config.ss_pin = SDCARD_CS1;
    spi0_config.frequency = freq;
    spi0_config.mode = mode;
    spi0_config.orc = 0x00;

    APP_ERROR_CHECK(nrf_drv_spi_init(&spi_0, &spi0_config, NULL, NULL)); // with blocking mode
  }
  else if (index == SPI1)
  {
    nrf_drv_spi_config_t spi1_config = NRF_DRV_SPI_DEFAULT_CONFIG;

    spi1_config.miso_pin = SPI1_MISO_PIN;
    spi1_config.mosi_pin = SPI1_MOSI_PIN;
    spi1_config.sck_pin = SPI1_SCK_PIN;
#if (SDCARD == ON)
    spi1_config.ss_pin =SDCARD_CS;
#endif

    spi1_config.frequency = freq;
    spi1_config.mode = mode;
    spi1_config.orc = 0x00;

    APP_ERROR_CHECK(nrf_drv_spi_init(&spi_1, &spi1_config, NULL, NULL)); // with blocking mode
  }
}

[Jared]

Hi,

It's not clear from the code that you've shared what the value that you set the slave select pin SDCARD_CS1 is.

• What is the nRF connected to via SPI?
• How are you measuring the state of the slave select pin? Logic analyzer, Oscilloscope? 
• What is SDCARD_CS1? Could you share more of your code?
• Which SDK and Softdevice version are you using?

regards

Jared

[dkj047]

Hi thanks

Soft device version is s140_nrf52_6.1.0_softdevice

I'm measuring the state of the slave select pin using oscilloscope

Two SPI instances are there and SDCARD_CS and SDCARD_CS1 are slave select pins (two gpio pin declared as output)

SPI communication is used to communicate with SD CARD.

[Jared]

Hi,

Could you share a project that will run on the nRF52840 DK? I would like reproduce it myself.

regards

Jared 

[dkj047]

Hi Jared 

I would not be able to share the whole project but I can tell  some of the details how I'm using  spi in my project.

 #define NRF_DRV_SPI_USE_SPIM  true                 //from nrf_drv_spi.h
 
 
 /* Serial Peripheral Interface Master with DMA */  //from nrf52840_peripherals.h
#define SPIM_PRESENT
#define SPIM_COUNT 4

#define SPI_INSTANCE_0          2 /**< SPI instance index. */  
#define SPI_INSTANCE_1          1 /**< SPI instance index. */ 

static const nrf_drv_spi_t spi_0 = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE_0);  
static const nrf_drv_spi_t spi_1 = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE_1);  

//gpios for spi0
#define SDCARD_CS1                 30 //SIO_30
#define SPI0_SCK_PIN               26 
#define SPI0_MISO_PIN              27  
#define SPI0_MOSI_PIN              31

//gpios for spi1
#define SDCARD_CS                  03 //SIO_03
#define SPI1_MISO_PIN              28
#define SPI1_MOSI_PIN              29
#define SPI1_SCK_PIN               45

    
nrf_drv_spi_t spi_0;// = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE);  /**< SPI instance. */
nrf_drv_spi_t spi_1;// = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE);  /**< SPI instance. */

void spi_set(nrf_drv_spi_t spi0, nrf_drv_spi_t spi1)
{
  spi_0 = spi0;
  spi_1 = spi1;
}
void  peripheral_init(void)
{
    spi_set(spi_0, spi_1);
    spi_open(SPI0, NRF_SPI_FREQ_8M, NRF_DRV_SPI_MODE_0);
#if (SDCARD == ON)
    spi_open(SPI1, NRF_SPI_FREQ_250K, NRF_DRV_SPI_MODE_3); //SD card frequency range 100-400 KHz while initializing
#endif

 nrf_gpio_cfg_output(SDCARD_CS);
 nrf_gpio_cfg_output(SDCARD_CS1);
}

bool spi_open(uint8_t index, nrf_drv_spi_frequency_t freq, nrf_drv_spi_mode_t mode)
{

  if (index == SPI0)
  {
    nrf_drv_spi_config_t spi0_config = NRF_DRV_SPI_DEFAULT_CONFIG;

    spi0_config.miso_pin = SPI0_MISO_PIN;
    spi0_config.mosi_pin = SPI0_MOSI_PIN;
    spi0_config.sck_pin = SPI0_SCK_PIN;  
      
    spi0_config.ss_pin = SDCARD_CS1;
    spi0_config.frequency = freq;
    spi0_config.mode = mode;
    spi0_config.orc = 0x00;

    APP_ERROR_CHECK(nrf_drv_spi_init(&spi_0, &spi0_config, NULL, NULL)); // with blocking mode
  }
  else if (index == SPI1)
  {
    nrf_drv_spi_config_t spi1_config = NRF_DRV_SPI_DEFAULT_CONFIG;

    spi1_config.miso_pin = SPI1_MISO_PIN;
    spi1_config.mosi_pin = SPI1_MOSI_PIN;
    spi1_config.sck_pin = SPI1_SCK_PIN;
#if (SDCARD == ON)
    spi1_config.ss_pin = SDCARD_CS;
#endif

    spi1_config.frequency = freq;
    spi1_config.mode = mode;
    spi1_config.orc = 0x00;

    APP_ERROR_CHECK(nrf_drv_spi_init(&spi_1, &spi1_config, NULL, NULL)); // with blocking mode
  }
}

/*******************************************************************************
 * @fn        select
 *
 * @brief     Select the card and wait for ready
 *
 * @return    none
 */
static int select(void)   /* 1:OK, 0:Timeout */
{
    /* Set SDCARD_CS low */
    SetPin(SDCARD_CS, LOW);
   /* Dummy clock (force DO enabled) */
    spi_write(SPI1, wBuf, 1);

    return 1;
}


/*******************************************************************************
 * @fn        deselect
 *
 * @brief      Deselect the card and release SPI bus
 *
 * @return    none
 */
static void deselect(void)
{
    /* Set SDCARD_CS high */
    SetPin(SDCARD_CS, HIGH);
    /* Dummy clock (force DO hi-z for multiple slave SPI) */
    spi_write(SPI1, wBuf, 1);
}

I'm calling the deselect function after every spi write to sd card but i'm still getting the ss/cs (slave/chip select) pin as low (ss pin monitored in oscilloscope.

[Jared]

Hi,

• Setting the slave select pin works but setting it high after a transfer doesn't work? Could you try disconnecting it from the output and see if it goes high?
• Does the SPI example in the SDK work with your board properly? 

regards

Jared