Hi, I'm currently designing a system which requires Heart Rate monitorization and I'm using the MAX30101 chip to do so. I will be using I2C communication and, therefore, based my code on the twi_sensor example for the nRF52 -DK dev kit. However, I just can not get any values from the sensor. Can anybody help me understand what I'm doing wrong? Thanks in advance.
#include <stdio.h>
#include "boards.h"
#include "app_util_platform.h"
#include "app_error.h"
#include "nrf_drv_twi.h"
#include "nrf_delay.h"
#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"
/* TWI instance ID. */
#define TWI_INSTANCE_ID 0
/* Common addresses definition for temperature sensor. */
#define LM75B_ADDR (0x90U >> 1)
#define MAX30101_ADDRESS 0x57
#define MAX30101_CONF_REG 0x09
#define MAX30101_MODE_HR 0x02
#define MAX30101_MODE_SPO2 0x03
#define MAX30101_FIFO_DATA 0x07
#define MAX30101_FIFO_WR_PT 0x04
#define MAX30101_FIFO_RD_PT 0x06
#define LM75B_REG_TEMP 0x00U
#define LM75B_REG_CONF 0x01U
#define LM75B_REG_THYST 0x02U
#define LM75B_REG_TOS 0x03U
/* Mode for LM75B. */
#define NORMAL_MODE 0U
/* Indicates if operation on TWI has ended. */
static volatile bool m_xfer_done = false;
/* TWI instance. */
static const nrf_drv_twi_t m_twi = NRF_DRV_TWI_INSTANCE(TWI_INSTANCE_ID);
/* Buffer for samples read from temperature sensor. */
static uint8_t m_sample;
static uint8_t m_wr_ptr, m_rd_ptr, m_num_samples;
static uint8_t tx_fifo[2];
/**
* @brief Function for setting active mode on MMA7660 accelerometer.
*/
void LM75B_set_mode(void)
{
ret_code_t err_code;
/* Writing to LM75B_REG_CONF "0" set temperature sensor in NORMAL mode. */
uint8_t reg[2] = {MAX30101_CONF_REG, MAX30101_MODE_SPO2};
err_code = nrf_drv_twi_tx(&m_twi, MAX30101_ADDRESS, reg, sizeof(reg), false);
APP_ERROR_CHECK(err_code);
while (m_xfer_done == false);
/* Writing to pointer byte. */
reg[0] = MAX30101_FIFO_WR_PT;
m_xfer_done = false;
err_code = nrf_drv_twi_tx(&m_twi, MAX30101_ADDRESS, reg, 1, false);
APP_ERROR_CHECK(err_code);
while (m_xfer_done == false);
err_code = nrf_drv_twi_rx(&m_twi, MAX30101_ADDRESS, &m_wr_ptr, sizeof(m_wr_ptr));
APP_ERROR_CHECK(err_code);
while (m_xfer_done == false);
}
/**
* @brief Function for handling data from temperature sensor.
*
* @param[in] temp Temperature in Celsius degrees read from sensor.
*/
__STATIC_INLINE void data_handler(uint8_t temp)
{
NRF_LOG_INFO("Values SpO2: %d .", temp);
}
/**
* @brief TWI events handler.
*/
void twi_handler(nrf_drv_twi_evt_t const * p_event, void * p_context)
{
switch (p_event->type)
{
case NRF_DRV_TWI_EVT_DONE:
if (p_event->xfer_desc.type == NRF_DRV_TWI_XFER_RX)
{
data_handler(m_sample);
}
m_xfer_done = true;
break;
default:
break;
}
}
/**
* @brief UART initialization.
*/
void twi_init (void)
{
ret_code_t err_code;
const nrf_drv_twi_config_t twi_lm75b_config = {
.scl = ARDUINO_SCL_PIN,
.sda = ARDUINO_SDA_PIN,
.frequency = NRF_DRV_TWI_FREQ_100K,
.interrupt_priority = APP_IRQ_PRIORITY_HIGH,
.clear_bus_init = false
};
err_code = nrf_drv_twi_init(&m_twi, &twi_lm75b_config, twi_handler, NULL);
APP_ERROR_CHECK(err_code);
nrf_drv_twi_enable(&m_twi);
}
/**
* @brief Function for reading data from temperature sensor.
*/
static void read_sensor_data()
{
ret_code_t err_code;
m_xfer_done = false;
/* Writing to pointer byte. */
tx_fifo[0] = MAX30101_FIFO_RD_PT;
m_xfer_done = false;
err_code = nrf_drv_twi_tx(&m_twi, MAX30101_ADDRESS, tx_fifo, 1, false);
APP_ERROR_CHECK(err_code);
while (m_xfer_done == false);
/* Read 1 byte from the specified address - skip 3 bits dedicated for fractional part of temperature. */
err_code = nrf_drv_twi_rx(&m_twi, MAX30101_ADDRESS, &m_sample, sizeof(m_sample));
APP_ERROR_CHECK(err_code);
}
/**
* @brief Function for main application entry.
*/
int main(void)
{
APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
NRF_LOG_DEFAULT_BACKENDS_INIT();
NRF_LOG_INFO("\r\nTWI sensor example started.");
NRF_LOG_FLUSH();
twi_init();
NRF_LOG_INFO("\r\nI2C Communication initialized.");
NRF_LOG_FLUSH();
LM75B_set_mode();
NRF_LOG_INFO("\r\nMAX30101 Initialized.");
NRF_LOG_FLUSH();
while (true)
{
nrf_delay_ms(500);
do
{
__WFE();
}while (m_xfer_done == false);
read_sensor_data();
NRF_LOG_FLUSH();
}
}
