Using nrf52832 as SPI master to get data from sensor

[lsvw1217]

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
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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 "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

[lsvw1217]

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 

[Marjeris Romero]

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

[lsvw1217]

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 

[Marjeris Romero]

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

[lsvw1217]

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

[Marjeris Romero]

Hi Vincent,

You also need to connect GND together.

BR,

Marjeris.