How to read FIFO Data from MAX30100 using STM32F4

Question

i'm monitorating heart rate by the MAX30100( https://img.filipeflop.com/files/download/Datasheet_MAX30100.pdf ) using the MCU STM32F4. I'm trying read the IR and RED data from the FIFO, but all returns are ZERO . The method MAX30100_Get_Num_Samples() returns 8 . I modeled the code using the pseudo code from datasheet of MAX30100. I tried several solutions for my problem but doesn't work. I dont know if i'm following the right way to get data from the FIFO. My code:

I2C_HandleTypeDef hi2c3; //i2c used
uint16_t RED[50] = {0}, IR[50] = {0}; //buffers for RED and IR
uint8_t buffOximeter[5];
char buffer[32];

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_I2C3_Init();
  MX_USB_DEVICE_Init();

  MAX30100_Init();

  while (1)
  {
    uint8_t numSamples = MAX30100_Get_Num_Samples();
    MAX30100_Read_HeartBeat(numSamples);

    for(int i = 0; i < numSamples; i++)
    {
        sprintf(buffer, "Amostra %d: %d / %d\n\r", i , IR[i], RED[i]);
        CDC_Transmit_FS((char*)buffer, 50);
    }
  }
}

static void MX_I2C3_Init(void)
{
  hi2c3.Instance = I2C3;
  hi2c3.Init.ClockSpeed = 400000;
  hi2c3.Init.DutyCycle = I2C_DUTYCYCLE_2;
  hi2c3.Init.OwnAddress1 = 0;
  hi2c3.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c3.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c3.Init.OwnAddress2 = 0;
  hi2c3.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c3.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c3) != HAL_OK)
  {
    Error_Handler();
  }
}

void MAX30100_Init(void)
{
    HAL_I2C_Mem_Write(&hi2c3,0xAE,0x06,1,0x02,1,1000); //set heart rate mode
    HAL_I2C_Mem_Write(&hi2c3,0xAE,0x09,1,0xFF,1,1000); //i50 ledCurrent
    uint8_t sr = 0x01, pw = 0x3;
    HAL_I2C_Mem_Write(&hi2c3,0xAE,0x07,1,(sr<<2)|pw,1,1000); //sr100, pw1600
    HAL_Delay(50);
}

void MAX30100_Read_HeartBeat(uint8_t num)
{
    for(int i=0;i<num;i++)
    {
        HAL_I2C_Master_Transmit(&hi2c3,0x57,0xAE,1,1000); //adress + write mode
        HAL_I2C_Master_Transmit(&hi2c3,0x57,0x02,1,1000); //send fifo_wr_ptr
        HAL_I2C_Master_Transmit(&hi2c3,0x57,0xAF,1,1000); //adress + read mode
        uint8_t data;
        HAL_I2C_Master_Receive(&hi2c3,0x57,&data,1,1000); //read fifo_wr_ptr
        HAL_Delay(100);                                   //STOP
        HAL_I2C_Master_Transmit(&hi2c3,0x57,0xAE,1,1000); //adress + write mode
        HAL_I2C_Master_Transmit(&hi2c3,0x57,0x05,1,1000); //send adress fifo data
        HAL_I2C_Master_Transmit(&hi2c3,0x57,0xAF,1,1000); //adress + read mode
        HAL_I2C_Mem_Read(&hi2c3,0x57,0x05,1,&buffOximeter,4,1000); //read fifo data
        IR[i] = (buffOximeter[0] << 8) | buffOximeter[1];
        RED[i] = (buffOximeter[2] << 8) | buffOximeter[3];
        HAL_Delay(100);                                   //STOP
        HAL_I2C_Master_Transmit(&hi2c3,0x57,0xAE,1,1000); //adress + write mode
        HAL_I2C_Master_Transmit(&hi2c3,0x57,0x04,1,1000); //send adress fifo_rd_ptr
        HAL_Delay(100);
    }
}

int MAX30100_Get_Num_Samples(void)
{
    uint8_t wrPtr, rdPtr;
    HAL_I2C_Mem_Read(&hi2c3,0x57,0x02,1,&wrPtr,1,1000);
    HAL_Delay(50);
    HAL_I2C_Mem_Read(&hi2c3,0x57,0x04,1,&rdPtr,1,1000);
    HAL_Delay(50);
    return (abs( 16 + wrPtr - rdPtr ) % 16);
}

Answer 1

connect the interrupt output pin (pin 13 active low) to an interrupt control pin on the cpu.

setup your cpu to be interrupted when the device indicates some event ready

Then, still in your interrupt handler function, read register 0 and determine which data is ready,.

the referenced datasheet, approx page 14 lists the order of communication events needed. Note that the posted code is NOT following the specified order of communication events

page 16, register 7, indicates how to initialize the SPO2 for the desired mode of operation