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I2C problems with STM32L Discovery

Question asked by grossi.marco on Jul 10, 2015
I am trying to communicate with a ADT7410 I2C temperature sensor using a STM32L Discovery Board (PB6 for SCL and PB7 for SDA).

I configure the I2C with the following code:

void I2C_initialization(void)
{
  I2C_InitTypeDef  I2C_InitStructure;
  GPIO_InitTypeDef GPIO_InitStructure;


  /* Enable I2C and GPIO clocks */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C1, ENABLE);


  /* Configure I2C pins: SCL and SDA */
  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_6 | GPIO_Pin_7;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_40MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_Init(GPIOB, &GPIO_InitStructure);


  GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_I2C1);
  GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_I2C1);


  /* I2C configuration */
  I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;
  I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;
  I2C_InitStructure.I2C_OwnAddress1 = 0x00;
  I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;
  I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;
  I2C_InitStructure.I2C_ClockSpeed = 100000;


  /* I2C Peripheral Enable */
  I2C_Cmd(I2C1, ENABLE);
  /* Apply I2C configuration after enabling it */
  I2C_Init(I2C1, &I2C_InitStructure);
}

To read data from the sensor I use the following procedure call (with parameter reg_adrs 0x04):

uint16_t I2C_read2bytes(uint8_t reg_adrs)
  {
      uint8_t I2C_MSB, I2C_LSB;
      uint16_t I2C_total;


  while(I2C_GetFlagStatus(I2C1, I2C_FLAG_BUSY));


  /* Send START condition */
  I2C_GenerateSTART(I2C1, ENABLE);


  while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT));


  I2C_Send7bitAddress(I2C1, 0x48 << 1, I2C_Direction_Transmitter);


  while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED));


  I2C_SendData(I2C1, reg_adrs);


  while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_BYTE_TRANSMITTED));



  I2C_GenerateSTART(I2C1, ENABLE);

  while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_MODE_SELECT));

  I2C_Send7bitAddress(I2C1, (0x48 << 1) | (0x01), I2C_Direction_Receiver);


  while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED));


  I2C_MSB = I2C_ReceiveData(I2C1);


  while(!I2C_CheckEvent(I2C1, I2C_EVENT_MASTER_BYTE_RECEIVED));

  I2C_GenerateSTOP(I2C1, ENABLE);


  I2C_total = (uint16_t)(I2C_MSB);

  return I2C_total;
  }

However what I get in return is the decimal number 145 (0b10010001) that is the address byte I send with the second  I2C_Send7bitAddress function and not the byte the slave device sends (that is however wront, that is not the byte it should return).

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