SPI MOSI & MISO problems

[Franco Fischer]

Hi!

I have a custom board with a NRF52840 and some extra sensors for my application. I'm trying to comunicate with one SPI sensor but I have a little extrange behavior. I put my osciloscope on the MOSI, MISO and SCK pins and I don't have any signal on MISO and MOSI pins.

To test the hardware, I'm using the example of the SDK 17.0.2, located at \examples\peripheral\spi, with a little modifications for my board, here is my code:

#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"

#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[] = TEST_STRING;           /**< TX buffer. */
static uint8_t       m_rx_buf[sizeof(TEST_STRING) + 1];    /**< 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_init(BSP_INIT_LEDS);
    nrf_gpio_cfg_output(LED_1);

    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
    spi_config.ss_pin   = NRF_GPIO_PIN_MAP(0, 26);
    spi_config.miso_pin = NRF_GPIO_PIN_MAP(0, 8);
    spi_config.mosi_pin = NRF_GPIO_PIN_MAP(0, 6);
    spi_config.sck_pin  = NRF_GPIO_PIN_MAP(0, 4);
    APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, spi_event_handler, NULL));

    NRF_LOG_INFO("SPI example started.");

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

        APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, m_length, m_rx_buf, m_length));

        while (!spi_xfer_done)
        {
            __WFE();
        }

        NRF_LOG_FLUSH();

        nrf_gpio_pin_toggle(LED_1);
        nrf_delay_ms(200);
    }
}

I'm missing some configuration?

Thanks!

[haakonsh]

That seems fine, I'd double check the pin mappings though. 

What pin is LED_1 configured to use?

[Franco Fischer]

Hi! I have a define on custom_board.h:

#define LED_1 NRF_GPIO_PIN_MAP(1, 10) // Blue

I have a little experience on Nordic, but I never use the SPI...

The example need extra configuration on the sdk_config.h ?

thanks!

[Franco Fischer]

I do more measuraments. I'm seeing a extrange behavior on MOSI pin, in the oscilloscope I see that the MOSI pin toggle at low frequency (about 16kHz). I disconnect my sensor and I see the same behavior. I attach the oscilloscope capture:

If I use another pin (I try with P1.09) works fine. I attach the oscilloscope capture:

Thanks!

[hmolesworth]

Most likely you have a pin defined elsewhere, often some kind of default serial port. A tip is to search for all pins in all projects using the typical sdk_config.h format:

#define BLAH_BLAH_PIN   6
                      ^
                      |
variable number of spaces and tabs

You can search for all these in SES using a regular expression search; in the search box (ctrl-shift-f) check the "Regular Expression" and "Search Dependencies" boxes then search for the following:

_PIN[ *\t*]6

This will list all definitions where pin 6 is used by ignoring multiple spaces and tabs between _PIN and the pin number you are checking, 6 in this case.

blahblah\sdk_config.h:#define HCI_UART_TX_PIN 6

Edit: Also maybe search for "_PIN_MAP"

[Franco Fischer]

Thanks for your help! I found the error, the pin 6 is used by the UART in the nrf_log of the SDK.

I disabled the nrf_log and the UART in the sdk_config.h and works fine!

Thanks for your time and help!