Slow SPI performance with zephyr

[dwalton65]

SDK Environment: nRF Connect SDK v1.7.1

Target: Decawave DWM1001-DEV. This uses the nRF52832

A 5 byte SPI transfer is taking about 17us when using the nordic spim drivers and about 56us when using the zephyr spim drivers.

SPI CLK frequency = 8M

Would this be considered normal? The slow speed of the zephyr SPI drivers is causing problems in my application.

The zephyr drivers seem to be stable, but slow.

I set and clear a gpio testpin before and after the SPI transfer so I can measure the timing.

SPI timing with the nordic drivers

SPI timing with the zephyr drivers

"nrfx_spim.zip" uses the nordic drivers

"zephyr_spim.zip" uses the zephyr drivers

6763.nrfx_spim.zipzephyr_spim.zip

[dwalton65]

Saleh said:

How do you set the SS signal?

I had attached the source code for the two test cases in the first post.

I am using Zephyr OS build v2.6.99-ncs1-1. This is the version that came with nRF Connect SDK v1.7.1

The following is the source code for the zephyr test:

/*

 * Copyright (c) 2016 Intel Corporation

 *

 * SPDX-License-Identifier: Apache-2.0

 */

#include <zephyr.h>

#include <device.h>

#include <string.h>

#include <drivers/gpio.h>

#include <nrfx_spim.h>

#include <device.h>

#include <drivers/spi.h>

#include <devicetree/spi.h>

#include <assert.h>

#define SLEEP_TIME  (100)       // ms

#define SPI_BUF_SIZE (255)

const struct gpio_dt_spec test_j7_pin3 = {.port = DEVICE_DT_GET(DT_NODELABEL(gpio0)), .pin = 12, .dt_flags = GPIO_ACTIVE_HIGH};

const struct device* spi = DEVICE_DT_GET(DT_PARENT(DT_NODELABEL(dw1000_dev)));

const static struct spi_config spi_config_dw1000 = SPI_CONFIG_DT(DT_NODELABEL(dw1000_dev), SPI_WORD_SET(8), 0);

uint8_t tx_buf [SPI_BUF_SIZE];

uint8_t rx_buf [SPI_BUF_SIZE];

void setup_spim(void)

{

    if (!device_is_ready(spi_config_dw1000.cs->gpio_dev))

    {

      printk("ERROR: spi gpio_dev not ready");

      for(;;);

    }

    if (!device_is_ready(spi))

    {

      printk("ERROR: failed to open spi");

      for(;;);

    }

}

/*

* Setup output test pins for external monitoring.

*/

void testPin1Set()

{

    gpio_pin_set_dt(&test_j7_pin3, 1);

}

void testPin1Clear()

{

    gpio_pin_set_dt(&test_j7_pin3, 0);

}

void testPinsSetup()

{

    gpio_pin_configure_dt(&test_j7_pin3, GPIO_OUTPUT_INACTIVE);

}

void main(void)

{

    testPinsSetup();

    setup_spim();

    printk("NRFX SPIM sample\n");

    printk("Read DW1000 DWT_DEVICE_ID\n");

    while (1)

    {

        k_msleep(SLEEP_TIME);

        testPin1Set();

        const int length = 5;

        memset(tx_buf, 0, length);

        memset(rx_buf, 0, length);

        struct spi_buf spi_buf_tx = {.buf = tx_buf, .len = length};

        struct spi_buf spi_buf_rx = {.buf = rx_buf, .len = length};

        struct spi_buf_set spi_buf_set_tx = {.buffers = &spi_buf_tx, .count = 1};

        struct spi_buf_set spi_buf_set_rx = {.buffers = &spi_buf_rx, .count = 1};

        spi_transceive(spi, &spi_config_dw1000, &spi_buf_set_tx, &spi_buf_set_rx);

        testPin1Clear();

        // Expecting DWT_DEVICE_ID   (0xDECA0130)        //!< DW1000 MP device ID

        printk("Result = %x\n", *((uint32_t*) &rx_buf[1]));

    }

}