I want to make an optimized spi clock.

[odenwar]

The SDK version is using version 17 and I am using NRF52832.

I checked the following scope waveform for the next SPI communication.

   

Question

1. I want to remove the following area (delay).
             
   
   
2. Is it possible to change the voltage of that IO to 1.8 volts using the source code?

[awneil]

Looks like a Rigol scope? Note that they can save a screenshot to a USB stick - this will give a far clearer picture than a photo!

It's not the clock that needs "optimising" - it's the CS line.

So how are you currently managing the CS line?

[odenwar]

I used the basic example code used in the SDK.

I also want to get rid of the data that comes out after the clock (about 2 clocks).

If there should be, why should it exist?

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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"

#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 "No"
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. */

static uint8_t       send_buf[3] = {0,0,0}; 
static uint8_t       recived_buf[4];
static const uint8_t send_length     = sizeof(send_buf); 
/**
 * @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 (recived_buf[0] != 0)
    {
        NRF_LOG_INFO(" Received:");
        NRF_LOG_HEXDUMP_INFO(recived_buf, strlen((const char *)recived_buf));
    }
}

void spi_send(char addr, char Data_h, char Data_l){
// Reset rx buffer and transfer done flag
        memset(recived_buf, 0, send_length);
        spi_xfer_done = false;
  send_buf[0]     = addr;
  send_buf[1]     = Data_l;
  send_buf[2]     = Data_h;

 while (!spi_xfer_done)
        {
            __WFE();
        }

        NRF_LOG_FLUSH();

  nrf_drv_spi_transfer(&spi, send_buf, send_length, recived_buf, send_length);
}

int main(void)
{
    bsp_board_init(BSP_INIT_LEDS);

    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   = 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));

    NRF_LOG_INFO("SPI example started.");

    while (1)
    {
        
        
        spi_send(0x11,0x01,0x7f);
        //APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, m_length, m_rx_buf, m_length));

       

        bsp_board_led_invert(BSP_BOARD_LED_0);
        nrf_delay_ms(200);
    }
}

[awneil]

odenwar said:

data that comes out after the clock (about 2 clocks).

There is no data after the clock; that's just the MOSI returning to its idle 'low' state.