STM32F4-Not seeing an I2C signal

[JYang.4]

Hi,

I'm using an STM32F429 MCU and trying to connect to a sensor through I2C. However, I measured both I2C pins with an oscilloscope and they were not showing any clock pulse or a signal. Here's my code for initiation:

void MX_I2C1_Init(void)
{
 hi2c1.Instance = I2C1;
 hi2c1.Init.ClockSpeed = 100000;
 hi2c1.Init.DutyCycle = I2C_DUTYCYCLE_2;
 hi2c1.Init.OwnAddress1 = 0;
 hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
 hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
 hi2c1.Init.OwnAddress2 = 0;
 hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
 hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
 if (HAL_I2C_Init(&hi2c1) != HAL_OK)
 {
 Error_Handler();
 printf("I2C Initiation Failed!\r\n");
 }
}
 
void HAL_I2C_MspInit(I2C_HandleTypeDef* i2cHandle)
{
 
 GPIO_InitTypeDef GPIO_InitStruct;
 if(i2cHandle->Instance==I2C1)
 {
 __GPIOB_CLK_ENABLE();
 /* I2C1 clock enable */
 __I2C1_CLK_ENABLE();
 /**I2C1 GPIO Configuration 
 PB8 ------> I2C1_SCL
 PB9 ------> I2C1_SDA 
 */
 GPIO_InitStruct.Pin = GPIO_PIN_8|GPIO_PIN_9;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
 GPIO_InitStruct.Pull = GPIO_NOPULL;
 GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF4_I2C1;
 HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
 }
}

And the following code for testing:

 while (1)
 {
 unsigned char buf;
 HAL_I2C_Mem_Read(&hi2c1, 0x29, 4, I2C_MEMADD_SIZE_8BIT, buf, 1, 10000);
 printf("Testing!\r\n");
 HAL_Delay(1000);
 }

I believe I measured the correct pins(PB8 and PB9), but I was not even seeing an SCL signal. The slave device was not connected yet. Does it have to be connected to see a clock signal? Or is there anything wrong with the code? Thanks.

[JYang.4]

Problem solved after connecting the sensor to the MCU.