SPI clock pin configuration for nRF52840.

[Shivek]

Hi,

I am using nRF52840 on custom board. I am trying to configure SPI pins, but I am not getting anything on the clock pin. I can see the chip select pin going low and high which is good. But there is no clock on the pin. Following is the code snippet from my project.

#define MEM_CS                           NRF_GPIO_PIN_MAP(0,4)
#define MEM_SI                           NRF_GPIO_PIN_MAP(0,7)
#define MEM_SO                           NRF_GPIO_PIN_MAP(1,8)
#define MEM_SCK                          NRF_GPIO_PIN_MAP(0,13)

void memInit(void)
{
	    //GPIO configuration
        nrf_gpio_cfg_output(MEM_CS);
        nrf_gpio_cfg_output(MEM_SI);
        nrf_gpio_cfg_output(MEM_SCK);
        nrf_gpio_cfg_input(MEM_SO, GPIO_PIN_CNF_PULL_Pulldown);

                
        //SPI configuration
        nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
        spi_config.ss_pin    = MEM_CS;
        spi_config.miso_pin  = MEM_SO;
        spi_config.mosi_pin  = MEM_SI;
        spi_config.sck_pin   = MEM_SCK;
        spi_config.bit_order = NRF_SPI_BIT_ORDER_MSB_FIRST;
        spi_config.frequency = NRF_SPI_FREQ_250K;
        spi_config.mode      = NRF_SPI_MODE_2;
        
        nrf_drv_spi_init(&spi, &spi_config, spi_event_handler, NULL);

}

uint32_t memId()
{
        __disable_irq();
        
        nrf_gpio_pin_clear(MEM_CS);         //Pin goes low now

        err  = nrf_drv_spi_transfer(&spi, p_tx_buffer, sizeof(tx_buffer), NULL, 0);  
        nrf_delay_ms(100);
        
        nrf_gpio_pin_set(MEM_CS);           //Pin goes high now

	    __enable_irq();
        return err;
}

For my custom board configuration I have set Preprocessor definitions to BOARD_CUSTOM. But for simplicity, I have defined the pins in the source code file. I am thinking to test it first and then I can define the pins for SPI in custom_board.h. On the custom board I have checked for the pins they are not connected to any other peripheral. 

For development, I am using SES with nRF SDK15.0.0 and Softdevice S140. 

Any insight would be appreciated.

Thanks!

[Einar Thorsrud]

Good points. Shivek: Perhaps it is worth configuring the SCK and other pins as normal GPIOs that you toggle, and check with a logic analyzer to verify that the pin mapping is actually what you think it is?

[Shivek]

Hi Hmolesworth,

Thanks for your time to give it a look. I have tried using P0.13 from nRF52840 as normal GPIO, and I was able to control the state of the pin, i.e., toggle the pin after some time. So, that's why I am sure about pin P0.13 and on top of that I tested with multimeter there is a connection from M2 connector pin(the pin which is connected to nRF52840 P0.13 pin on the LN60E840E module) to the connector header on the dev kit. 

Regards,

Shivek

[Shivek]

Hi Einar, 

As I mentioned in my response to hmolesworth, I have tried using P0.13 as normal GPIO and tested toggling the pin, I was able to see the pin toggling on scope. But if I am using the same pin for SPI clock, it won't get any clock going on that pin.

Would you be able to send a simple example(other than which is included in SDK), which I can test on my hardware just by simply changing the pins?

 I think that would make me clear that whether its a hardware issue or software issue.

Regards,

Shivek

[hmolesworth]

I am not getting anything on the clock pin -- at 250kHz clock I would think even a cheap 'scope would see that, but are you using (say) some low-cost analyser which might have too low a resolution?

p_tx_buffer,and sizeof(tx_buffer) are inconsistent (different buffers), maybe make the buffer size bigger so easier to see the clocks. Hopefully the buffer is not defined const ..

[Einar Thorsrud]

Hi Shivek,

I see you ask for an example which is not included in the SDK, but did you try the SPI Master Example? That is quite simple so if I was to make another example it would be basically the same. Have you tested that on your HW?