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Using nrf52832 as SPI master to get data from sensor

Hi All,

I'm trying to use the nrf52832 as the SPI master to get sensor reading through spi from another sensor. I want to base my firmware on the spi_pca10040 example but I don't know what the change except the pin number for CS, MISO, MOSI, and SCLK and the length of the tx and rx buffer. (since the sensor send 32 bits data)

/**
 * Copyright (c) 2015 - 2018, Nordic Semiconductor ASA
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 *
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 *
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
#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[4];           /**< TX buffer. */
static uint8_t       m_rx_buf[4];    /**< 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);

    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   = 29; //SPI_SS_PIN;
    spi_config.miso_pin = 28; //SPI_MISO_PIN;
    spi_config.mosi_pin = 4; //SPI_MOSI_PIN;
    spi_config.sck_pin  = 3; //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)
    {
        // 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();

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

This is what I have so far. Any advice?

Thanks,

Vincent

Parents
  • Hi,

    Thank you for the speedy reply. We are working with the max30001 sensor and we plan to record ECG data with it. I'll post the link for the datasheet and its header and library file below. 

    https://datasheets.maximintegrated.com/en/ds/MAX30001.pdf  (datasheet)

    https://os.mbed.com/users/asilva14/code/HSP_RPC_GUI/file/0fdc04a80278/HSP/Devices/MAX30001/MAX30001/MAX30001.cpp/ (.cpp)

    https://os.mbed.com/users/asilva14/code/HSP_RPC_GUI/file/0fdc04a80278/HSP/Devices/MAX30001/MAX30001/MAX30001.h/ (.h)

    As for the number of bytes, I think it's actually 3 bytes of data and 1 bytes of address if I'm not mistaken.

    Thank you,

    Vincent 

  • Yes, you are right, the sensor uses 3 bytes of data and 1 byte for command word (adress[6:0] + R/W). The next step would be to try to read some data from the ECG_DATA register. For debugging purposes you can enable the NRF_LOG_UART module in sdk_config.h and open a uart terminal (i.e. Termite) so you can monitor the received bytes.

    - Marjeris

  • Hi,

    I’m very new to coding so sorry if my questions are obvious. But where in the code should I put in the register for the ECG data? And what format should I followed? Could you give me a brief example?

    Thanks,

    Vincent 

  • Hi Vincent,

    The message you want to send needs to be stored in the tx buffer "m_tx_buf". And the data transfer is done by "nrf_drv_spi_transfer()" function. So as I understand the datasheet for the MAX30001 m_tx_buf[0] should contain the adress[6:0] of the register you want to write to, and a bit for indicating if this is a read (1) or write (0) command.

    So as an example you can write inside the main function:

    		uint8_t adress=0x0F;    //The adress of the INFO register
    		uint8_t message= (adress<<1)+1;     //Add the Read command
    		m_tx_buf[0]=message;

    Here we shift the adress one bit to the left and add a bit for either read(1) or write(0) as the MAX30001 specifies. If you are not familiar with bitwise operations in C you can take a look at this wikipedia article.

    This should read the value store in the INFO register. Try to read from a register with a known value the first time just to verify that your SPI interface is working.  Then you can try to read from ECG FIFO Normal Mode Read Back register (0x21). You will need to see the chapter "FIFO Memory Description" and the read back examples in the Datasheet to understand the output from the sensor.

    BR,

    Marjeris

  • Hi Marjesic,

    I tried the code to read value from the INFO register but all I get from Termite is

    " <info> app: Transfer completed. "

    over and over again.

    Seems like the tx_buffer coming out from mosi is never received by the maxim chip.

    The following is the code I used.

    /**
     * Copyright (c) 2015 - 2018, Nordic Semiconductor ASA
     *
     * All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without modification,
     * are permitted provided that the following conditions are met:
     *
     * 1. Redistributions of source code must retain the above copyright notice, this
     *    list of conditions and the following disclaimer.
     *
     * 2. Redistributions in binary form, except as embedded into a Nordic
     *    Semiconductor ASA integrated circuit in a product or a software update for
     *    such product, must reproduce the above copyright notice, this list of
     *    conditions and the following disclaimer in the documentation and/or other
     *    materials provided with the distribution.
     *
     * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
     *    contributors may be used to endorse or promote products derived from this
     *    software without specific prior written permission.
     *
     * 4. This software, with or without modification, must only be used with a
     *    Nordic Semiconductor ASA integrated circuit.
     *
     * 5. Any software provided in binary form under this license must not be reverse
     *    engineered, decompiled, modified and/or disassembled.
     *
     * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
     * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
     * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
     * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
     * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     *
     */
    #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[4];           /**< TX buffer. */
    static uint8_t       m_rx_buf[4];    /**< 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);
    
        APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
        NRF_LOG_DEFAULT_BACKENDS_INIT();
    
    uint8_t adress=0x0F;    //The adress of the INFO register
    uint8_t message= (adress<<1)+1;     //Add the Read command
    m_tx_buf[0]=message;
    
        nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
        spi_config.ss_pin   = SPI_SS_PIN; //29
        spi_config.miso_pin = SPI_MISO_PIN; //28
        spi_config.mosi_pin = SPI_MOSI_PIN; //4
        spi_config.sck_pin  = SPI_SCK_PIN; //3
        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();
    
            bsp_board_led_invert(BSP_BOARD_LED_0);
            nrf_delay_ms(1000);
        }
    }

    As for the hardware side, I connect the following:

    nrf52832 --> max30001

      SS                   CS

    MOSI                SDI

    MISO                SDO

    SCK                  SCK

    Where did I messed up? Is it software or hardware problem?

    Thank you,

    Vincent

Reply
  • Hi Marjesic,

    I tried the code to read value from the INFO register but all I get from Termite is

    " <info> app: Transfer completed. "

    over and over again.

    Seems like the tx_buffer coming out from mosi is never received by the maxim chip.

    The following is the code I used.

    /**
     * Copyright (c) 2015 - 2018, Nordic Semiconductor ASA
     *
     * All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without modification,
     * are permitted provided that the following conditions are met:
     *
     * 1. Redistributions of source code must retain the above copyright notice, this
     *    list of conditions and the following disclaimer.
     *
     * 2. Redistributions in binary form, except as embedded into a Nordic
     *    Semiconductor ASA integrated circuit in a product or a software update for
     *    such product, must reproduce the above copyright notice, this list of
     *    conditions and the following disclaimer in the documentation and/or other
     *    materials provided with the distribution.
     *
     * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
     *    contributors may be used to endorse or promote products derived from this
     *    software without specific prior written permission.
     *
     * 4. This software, with or without modification, must only be used with a
     *    Nordic Semiconductor ASA integrated circuit.
     *
     * 5. Any software provided in binary form under this license must not be reverse
     *    engineered, decompiled, modified and/or disassembled.
     *
     * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
     * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
     * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
     * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
     * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     *
     */
    #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[4];           /**< TX buffer. */
    static uint8_t       m_rx_buf[4];    /**< 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);
    
        APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
        NRF_LOG_DEFAULT_BACKENDS_INIT();
    
    uint8_t adress=0x0F;    //The adress of the INFO register
    uint8_t message= (adress<<1)+1;     //Add the Read command
    m_tx_buf[0]=message;
    
        nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
        spi_config.ss_pin   = SPI_SS_PIN; //29
        spi_config.miso_pin = SPI_MISO_PIN; //28
        spi_config.mosi_pin = SPI_MOSI_PIN; //4
        spi_config.sck_pin  = SPI_SCK_PIN; //3
        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();
    
            bsp_board_led_invert(BSP_BOARD_LED_0);
            nrf_delay_ms(1000);
        }
    }

    As for the hardware side, I connect the following:

    nrf52832 --> max30001

      SS                   CS

    MOSI                SDI

    MISO                SDO

    SCK                  SCK

    Where did I messed up? Is it software or hardware problem?

    Thank you,

    Vincent

Children
  • Hi Vincent,

    You also need to connect GND together.

    BR,

    Marjeris.

  • Hi Marjeris,

    Yes, I did connect the both GND together. I also tried using logical analyzer (analog discovery) and see the signal coming from nRF52832 with SPI master firmware. But I couldn't see any signal. However, I'm certain that the firmware works because when I connect nRF52832 with SPI master firmware and nRF52840 with SPI slave firmware, it did work. 

    Any suggestion?

    Thanks,

    Vincent

  • Hi Marjeris,

    So after some logical analyzer debugging. I'm now able to see signal from SS,MOSI, and SCLK but not MISO. Here's a screenshot of the result. 

    DIO4 is SS. 

    DIO5 is MISO

    DIO6 is MOSI 

    DIO7 is SCLK

    Here's the code I used 

    /**
     * Copyright (c) 2015 - 2018, Nordic Semiconductor ASA
     *
     * All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without modification,
     * are permitted provided that the following conditions are met:
     *
     * 1. Redistributions of source code must retain the above copyright notice, this
     *    list of conditions and the following disclaimer.
     *
     * 2. Redistributions in binary form, except as embedded into a Nordic
     *    Semiconductor ASA integrated circuit in a product or a software update for
     *    such product, must reproduce the above copyright notice, this list of
     *    conditions and the following disclaimer in the documentation and/or other
     *    materials provided with the distribution.
     *
     * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
     *    contributors may be used to endorse or promote products derived from this
     *    software without specific prior written permission.
     *
     * 4. This software, with or without modification, must only be used with a
     *    Nordic Semiconductor ASA integrated circuit.
     *
     * 5. Any software provided in binary form under this license must not be reverse
     *    engineered, decompiled, modified and/or disassembled.
     *
     * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
     * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
     * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
     * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
     * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     *
     */
    #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 "MAX30001t.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[4] = {0x0F,0x55,0xaa,0x55};           /**< TX buffer. */
    static uint8_t       m_rx_buf[4];    /**< 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);
    
        APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
        NRF_LOG_DEFAULT_BACKENDS_INIT();
    
    uint8_t adress=0x0F;    //The adress of the INFO register
    uint8_t message= (adress<<1)+1;     //Add the Read command
    m_tx_buf[0]=message;
    
        nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
        spi_config.ss_pin   = SPI_SS_PIN; //29
        spi_config.miso_pin = SPI_MISO_PIN; //28
        spi_config.mosi_pin = SPI_MOSI_PIN; //4
        spi_config.sck_pin  = SPI_SCK_PIN; //3
        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, 6));
    
            while (!spi_xfer_done)
            {
                __WFE();
            }
    
            NRF_LOG_FLUSH();
    
            bsp_board_led_invert(BSP_BOARD_LED_0);
            nrf_delay_ms(1000);
        }
    }
    

    I tried reading from both the INFO register (0x0F) and the ECG register (0x21). But the results both show no signal in MISO. 

    Thank you,

    Vincent

  • Hi Vincent,

    You can try to increase the RX buffer to 8 bytes and see if you get something else than zeroes. It can be that the first bytes of data from the sensor are dummy bytes.

    It seems like the SPI is working fine in the nRF52 side, but you are only getting zeroes from the maxim chip. You will need to match the SPI configuration of the maxim chip to be able to read data from it.

    If you want to do a quick check that your MISO pin in the nRF52 is working find you can do a loopback test, just connect MOSI to MISO in the nRF52 DK and read the received bytes in Termite. But it seems like everything is working fine on the nRF52 DK side, so there have to be something in the way we send data that is not matching to what the maxim chip is expecting.

    Sometimes we have to check if the sensor is expecting MSB or LSB first, and which SPI mode the sensor is expecting. You can configure this in by changing NRF_DRV_DEFAULT_CONFIG in nrf_drv_spi.h

    The spi master example is configured in SPI mode 0 (SCK active high, sample on leading edge of clock, CPOL=0/CPHA=0) and MSB is shifted out first by default. But this should be compatible with the maxim chip (page 36 of the datasheet) so I don't know what the problem could be. I recommend you to take a look at the timing diagrams of the maxim chip and see if there is something we have missed out. And try a little bit more of debugging, you can try to send LSB first instead of MSB for example and see if that works.

    Best Regards,

    Marjeris

  • Hi Marjeris,

    Ya I think the spi on both nRF52 and maxim works. I just have to get them to communicate. 

    So when I was trying to read from the ECG register again today, some signal appear on the MISO.

    There appears to be a peak at the falling edge of the 29th clk. But I'm not sure why it's there since the rx_buffer didn't return anything.

    Another thing I want to try is to initiate the ECG by writing to a config register (0x10). One of the index in this register allows us to enable ECG. (This is on pg.48 of the max30001 datasheet) Could you provide an example on how to write to the index of the config register?

    Thank you very much for your help,

    Vincent

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