Why HAL_I2C_IsDeviceReady return HAL_ERROR

1) Set PA8 and PC9 with GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;

HIGH or VERY_HIGH setting is not good.

2) Try to roll the counter up to 255. =>

    for(counter = 0 ; counter < 255; counter++)

I think the dev address has to be shifted 1 bit to the left.

3) Check that you have actual (2.7K for example) pull_up resistors on the I2C lines,

GPIO_InitStruct.Pull = GPIO_PULLUP, is often not enough.

I switch the frequencies at "stm32f4xx_hal_msp.c" file

I change my counter to 255

and lastly, I put a 4.7k resistor to SDA and SDC each, one terminal connected to the line another terminal connected to the 5V supply at STM. for both lines.

Still can't get rid of the HAL_ERROR

Next step for me would be to check with the scope whether there is something on SDA/SCL.

I am getting error in this line

  while (I2C_Trials < Trials);

  hi2c->State = HAL_I2C_STATE_READY;

  /* Process Unlocked */

  __HAL_UNLOCK(hi2c);

  return HAL_ERROR;

What chip are you trying to talk with? The 7-bit slave address should be shifted left one bit. You're only checking for half of the possible slave values.

Let me correct my self, I got HAL_OK at counter 0 and 1, not in 2.

Also I change my code to more clear debugging, but still doesn't get anything.

 while (1)

 {

  /* USER CODE END WHILE */

  /* USER CODE BEGIN 3 */

 for(counter = 0 ; counter < 255; counter++)

 {

 IDR_Result = HAL_I2C_IsDeviceReady(&hi2c3, counter, 3, 10);

 if(IDR_Result == HAL_OK)

 {

 I2C_Address = counter;

 HAL_GPIO_TogglePin(GPIOG, GPIO_PIN_14);

 }

 }

 HAL_GPIO_TogglePin(GPIOG, GPIO_PIN_13);

 HAL_Delay(500);

 }

 /* USER CODE END 3 */

OKAY NOW,

I got I2C addresses of

0-1-78-79-130-131

Tomorrow, I'll connect Arduino with known addresses.

So that I could say something, for now, THANKS TO ALL OF YOU!