SPI Tx & Rx failure

[Ree Wang]

Hi DevZone, 

I am doing my project base on SDK 14.2.0 example spi. I modified the PIN according to Arduino PIN map and connected the nRF52480 Preview DK with Arduino Uno. When I run spi example program, Arduino board does receive the data over SPI. However, when I add my own code, Arduino board cannot receive the data. I think I must incorrectly use the API nrf_drf_spi_transfer(), but I could not find the mistakes...  

Example Code:

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

My Code:

uint8_t tx_data = 5;
uint8_t dummy_receive;
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, &tx_data, 1, &dummy_receive, 1));

Attached file is the main.c file... Could you please tell me what is the problem? 

Fullscreen main.c Download

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#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 "SEGGER_RTT.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;
    SEGGER_RTT_printf(0, "Transfer completed.");
    if (m_rx_buf[0] != 0)
    {
        SEGGER_RTT_printf(0, " 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();
    
    SEGGER_RTT_printf(0, "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;
    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;

        //APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, m_length, m_rx_buf, m_length));
        
        uint8_t tx_data = 5;
        uint8_t dummy_receive;
        APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, &tx_data, 1, &dummy_receive, 1));


        while (!spi_xfer_done)
        {
            __WFE();
        }

        NRF_LOG_FLUSH();

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

[Jørgen Holmefjord]

Hi,

I treied your code and can see data being output on MOSI line. How are you seeing that the Arduino does not receiving the data? Have you checked the SPI bus lines using a logic analyzer, to see if anything is sendt?

Note this errata if you are using Eng A revision of nRF52840, with a single byte being sendt using SPI (with EasyDMA enabled).

I modified the PIN according to Arduino PIN

Which pins did you use?

Best regards,
Jørgen

[Jørgen Holmefjord]

I tested with P1.12-P1.15 pins as well and I'm still seeing data being transmitted. Have you tried sending more bytes? What does the Arduino SPI slave expect? Will it print logs on any data received? Do you have a link to the code of the Arduino example? I would really recommend getting a logic analyzer for debugging issues like this.

[Ree Wang]

I am using nRF52480 Preview Development Kit. When I send more than one bytes, for example:

uint8_t tx_data[] = {5,1};
uint8_t dummy_receive[] = {0,0};
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, tx_data, 2, dummy_receive, 2));

I still could not see the log in Arduino side.

Below is arduino code I am used. The original code can be find in the link: https://arduino.stackexchange.com/questions/16348/how-do-you-use-spi-on-an-arduino

// what to do with incoming data
volatile byte command = 0;

void setup (void)
  {
  Serial.begin(9600);
  // have to send on master in, *slave out*
  pinMode(MISO, OUTPUT);

  // turn on SPI in slave mode
  SPCR |= _BV(SPE);

  // turn on interrupts
  SPCR |= _BV(SPIE);

  }  // end of setup


// SPI interrupt routine
ISR (SPI_STC_vect)
  {
  byte c = SPDR;

  if (command==1)

      SPDR = c -5;  
      Serial.print("rx:);
      Serial.println(c, Hex); 
      break;

  }  // end of interrupt service routine (ISR) SPI_STC_vect

void loop (void)
  {

  // if SPI not active, clear current command
  if (digitalRead (SS) == HIGH)
    command = 0;
  else command = 1;
  }  // end of loop

[Jørgen Holmefjord]

Do you still see "Transfer completed." on the RTT terminal from the nRF52840? You did connect slave select line to Arduino as well? Could you write exact pins connected from what to what (SS, SCK, MISO, MOSI)?

[Ree Wang]

Hi,

Yes. I see Transfer complete... I find some mistake in my Arduino SPI slave code. I have updated, then it can receive data from nRF52 DK. Transfer from master to slave is working well now. But still not working for slave to master. 

Since this questions of this ticket is solved, I would like to close it. I have create another ticket for slave to master transfer issue. 

devzone.nordicsemi.com/.../spi-master-cannot-receive-spi-slave-response

Thank you very much for your help!