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)

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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 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

[Marjeris Romero]

Hi Vincent,

To write to a register you just have to change the Read/Write bit to 0 as it's described in the MAX30001 datasheet.

		uint8_t adress=0x10;    //The adress of the register you want to read or write to
		uint8_t message= (adress<<1)+0;     //Add the Read(1)/Write(0) command
		m_tx_buf[0]=message;

You can try to enable the ECG Channel and try to read from the ECG register and see what happens. You should also try to increase the RX buffer as I suggested earlier.

Best Regards,

Marjeris