Posted on July 10, 2015 at 18:25I 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).
