STM32 I2C only sends address

Question

Hello I am trying to communicate with TI BQ28Z610 by using Nucleo-F746ZG. All I do is trying to read data from TI chip. I am sending 0x08 to slave address 0x55.I2C frequency is 80kHz and pull ups are 10 K. Here is the related part of the trial code:

while (1)
    {
        /* USER CODE END WHILE */

        /* USER CODE BEGIN 3 */
        //READ VOLTAGE FOR TESTING

#define I2C_Slave_Address (0x55) // Receive 0x55+1    0x55
        uint8_t I2C_Data[16];
        uint8_t I2C_DataToSend;
        char statusString[255];
        int statusStringLength;
        I2C_DataToSend=0x08;

        if (HAL_OK != HAL_I2C_Master_Transmit(&hi2c1,(uint8_t)I2C_Slave_Address,&I2C_DataToSend,1,1000)){
            statusStringLength = sprintf(statusString,"Transmit failed");
            CDC_Transmit_FS(statusString,statusStringLength);
            HAL_GPIO_WritePin(LD1_GPIO_Port,LD1_Pin,1);
        }




        if (HAL_OK != HAL_I2C_Master_Receive(&hi2c1,(uint8_t)I2C_Slave_Address + 1 , I2C_Data,1,1000)){

            statusStringLength = sprintf(statusString,"Receive failed");
            CDC_Transmit_FS(statusString,statusStringLength);
            HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin,1);

        }
        statusStringLength = sprintf(statusString,"Voltage: %d", (int) I2C_Data[0]);
        CDC_Transmit_FS(statusString,statusStringLength);
        HAL_Delay(100);
    }

Here is the oscilloscope image:

Here is the logic analyzor view:

So what might be the reason behind it? For me everything looks fine. Thank you beforehand. Edit: Here is the logic analyzer capture for 0xAA slave address:

Answer 1

The slave address is wrong. It is 0xAA for write and 0xAB for read. Your define has 0x16. The chip won't answer at that address, so you see the NAK after address 0x16 on the scope shot.

Answer 2

Per the logic analyzer view, you are receiving a NACK to the address, indicating that there is no slave at the address you are sending.

According to the BQ28Z610 Technical Reference, page 57 (here), the device has a slave address of 0x55 (7-bit) so unless you are using some sort of address translation chip, slave address 0x16 is wrong.

Try correcting the address.