Identical waveform I2C SCL and SDA lines

CGrov.1 · ‎2020-08-04

I am using an STM32L476RG and using I2C-1 and I2C-3 to connect to two different sensors. Both I2Cs have identical waveforms on the SCL and SDA lines when observed with an oscilloscope. This suggested a short to me, but the short is definitely not on the board as I have checked for continuity.

I am not sure that the short is inside the IC as every other function of the chip works fine, and I find it hard to believe that only the I2Cs failed while all other pins are still functioning.

Has anyone seen this before?

Tesla DeLorean · ‎2020-08-04

No

Check the AF settings for pins

Show a pin diagram

show initialization code for pins, and peripherals

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CGrov.1 · ‎2020-08-04

Here is the pin diagram from the IDE. The initialisation is also generated by the IDE:

static void MX_I2C1_Init(void)
{
 
  /* USER CODE BEGIN I2C1_Init 0 */
printf("I2C1 initializing...\n\r");
  /* USER CODE END I2C1_Init 0 */
 
  /* USER CODE BEGIN I2C1_Init 1 */
 
  /* USER CODE END I2C1_Init 1 */
  hi2c1.Instance = I2C1;
  hi2c1.Init.Timing = 0x00702991;
  hi2c1.Init.OwnAddress1 = 0;
  hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c1.Init.OwnAddress2 = 0;
  hi2c1.Init.OwnAddress2Masks = I2C_OA2_NOMASK;
  hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c1) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure Analogue filter 
  */
  if (HAL_I2CEx_ConfigAnalogFilter(&hi2c1, I2C_ANALOGFILTER_ENABLE) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure Digital filter 
  */
  if (HAL_I2CEx_ConfigDigitalFilter(&hi2c1, 0) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN I2C1_Init 2 */
  printf("I2C-1 initialized\n\r");
  /* USER CODE END I2C1_Init 2 */
 
}
 
/**
  * @brief I2C3 Initialization Function
  * @param None
  * @retval None
  */
static void MX_I2C3_Init(void)
{
 
  /* USER CODE BEGIN I2C3_Init 0 */
	printf("I2C3 initializing...\n\r");
  /* USER CODE END I2C3_Init 0 */
 
  /* USER CODE BEGIN I2C3_Init 1 */
 
  /* USER CODE END I2C3_Init 1 */
  hi2c3.Instance = I2C3;
  hi2c3.Init.Timing = 0x00702991;
  hi2c3.Init.OwnAddress1 = 0;
  hi2c3.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c3.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c3.Init.OwnAddress2 = 0;
  hi2c3.Init.OwnAddress2Masks = I2C_OA2_NOMASK;
  hi2c3.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c3.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c3) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure Analogue filter 
  */
  if (HAL_I2CEx_ConfigAnalogFilter(&hi2c3, I2C_ANALOGFILTER_ENABLE) != HAL_OK)
  {
    Error_Handler();
  }
  /** Configure Digital filter 
  */
  if (HAL_I2CEx_ConfigDigitalFilter(&hi2c3, 0) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN I2C3_Init 2 */
  printf("I2C-3 initialized\n\r");
  /* USER CODE END I2C3_Init 2 */
 
}

S.Ma · ‎2020-08-04

I think it's nearly impossible to have multiple GPIO electrically short within the package.

Also, unless using tricky interrupt scheme, most likely both I2C should be time shifted if the code runs them sequentially... or you are running the same code on both I2C.

The above code doesn't talk about GPIO pin settings, only peripheral setting...

Tesla DeLorean · ‎2020-08-04

Have the design tools output a Net List for your design, double check what naming/connectivity the tools are grouping together.

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CGrov.1 · ‎2020-08-04

It was my understanding that GPIO settings should no affect peripherals as long as they are not mapped to the same pin?

Here is the GPIO initialisation, also generated by the IDE.

static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
 
  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_10, GPIO_PIN_RESET);
 
  /*Configure GPIO pin : PC13 */
  GPIO_InitStruct.Pin = GPIO_PIN_13;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
 
  /*Configure GPIO pin : PC10 */
  GPIO_InitStruct.Pin = GPIO_PIN_10;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
 
}

Tesla DeLorean · ‎2020-08-04

Double check the clock/pin initialization code, probably the MSP file

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CGrov.1 · ‎2020-08-04

Is there anything particular I should be looking for?

hal_msp file:

void HAL_MspInit(void)
{
  /* USER CODE BEGIN MspInit 0 */
 
  /* USER CODE END MspInit 0 */
 
  __HAL_RCC_SYSCFG_CLK_ENABLE();
  __HAL_RCC_PWR_CLK_ENABLE();
 
  /* System interrupt init*/
 
  /* USER CODE BEGIN MspInit 1 */
 
  /* USER CODE END MspInit 1 */
}
 
/**
* @brief I2C MSP Initialization
* This function configures the hardware resources used in this example
* @param hi2c: I2C handle pointer
* @retval None
*/
void HAL_I2C_MspInit(I2C_HandleTypeDef* hi2c)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  if(hi2c->Instance==I2C1)
  {
  /* USER CODE BEGIN I2C1_MspInit 0 */
 
  /* USER CODE END I2C1_MspInit 0 */
  
    __HAL_RCC_GPIOB_CLK_ENABLE();
    /**I2C1 GPIO Configuration    
    PB6     ------> I2C1_SCL
    PB7     ------> I2C1_SDA 
    */
    GPIO_InitStruct.Pin = GPIO_PIN_6|GPIO_PIN_7;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF4_I2C1;
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
 
    /* Peripheral clock enable */
    __HAL_RCC_I2C1_CLK_ENABLE();
  /* USER CODE BEGIN I2C1_MspInit 1 */
 
  /* USER CODE END I2C1_MspInit 1 */
  }
  else if(hi2c->Instance==I2C3)
  {
  /* USER CODE BEGIN I2C3_MspInit 0 */
 
  /* USER CODE END I2C3_MspInit 0 */
  
    __HAL_RCC_GPIOC_CLK_ENABLE();
    /**I2C3 GPIO Configuration    
    PC0     ------> I2C3_SCL
    PC1     ------> I2C3_SDA 
    */
    GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_1;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF4_I2C3;
    HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
 
    /* Peripheral clock enable */
    __HAL_RCC_I2C3_CLK_ENABLE();
  /* USER CODE BEGIN I2C3_MspInit 1 */
 
  /* USER CODE END I2C3_MspInit 1 */
  }
 
}
 
/**
* @brief I2C MSP De-Initialization
* This function freeze the hardware resources used in this example
* @param hi2c: I2C handle pointer
* @retval None
*/
void HAL_I2C_MspDeInit(I2C_HandleTypeDef* hi2c)
{
  if(hi2c->Instance==I2C1)
  {
  /* USER CODE BEGIN I2C1_MspDeInit 0 */
 
  /* USER CODE END I2C1_MspDeInit 0 */
    /* Peripheral clock disable */
    __HAL_RCC_I2C1_CLK_DISABLE();
  
    /**I2C1 GPIO Configuration    
    PB6     ------> I2C1_SCL
    PB7     ------> I2C1_SDA 
    */
    HAL_GPIO_DeInit(GPIOB, GPIO_PIN_6|GPIO_PIN_7);
 
  /* USER CODE BEGIN I2C1_MspDeInit 1 */
 
  /* USER CODE END I2C1_MspDeInit 1 */
  }
  else if(hi2c->Instance==I2C3)
  {
  /* USER CODE BEGIN I2C3_MspDeInit 0 */
 
  /* USER CODE END I2C3_MspDeInit 0 */
    /* Peripheral clock disable */
    __HAL_RCC_I2C3_CLK_DISABLE();
  
    /**I2C3 GPIO Configuration    
    PC0     ------> I2C3_SCL
    PC1     ------> I2C3_SDA 
    */
    HAL_GPIO_DeInit(GPIOC, GPIO_PIN_0|GPIO_PIN_1);
 
  /* USER CODE BEGIN I2C3_MspDeInit 1 */
 
  /* USER CODE END I2C3_MspDeInit 1 */
  }
 
}
 
/**
* @brief TIM_Base MSP Initialization
* This function configures the hardware resources used in this example
* @param htim_base: TIM_Base handle pointer
* @retval None
*/
void HAL_TIM_Base_MspInit(TIM_HandleTypeDef* htim_base)
{
  if(htim_base->Instance==TIM1)
  {
  /* USER CODE BEGIN TIM1_MspInit 0 */
 
  /* USER CODE END TIM1_MspInit 0 */
    /* Peripheral clock enable */
    __HAL_RCC_TIM1_CLK_ENABLE();
  /* USER CODE BEGIN TIM1_MspInit 1 */
 
  /* USER CODE END TIM1_MspInit 1 */
  }
 
}
 
/**
* @brief TIM_Base MSP De-Initialization
* This function freeze the hardware resources used in this example
* @param htim_base: TIM_Base handle pointer
* @retval None
*/
void HAL_TIM_Base_MspDeInit(TIM_HandleTypeDef* htim_base)
{
  if(htim_base->Instance==TIM1)
  {
  /* USER CODE BEGIN TIM1_MspDeInit 0 */
 
  /* USER CODE END TIM1_MspDeInit 0 */
    /* Peripheral clock disable */
    __HAL_RCC_TIM1_CLK_DISABLE();
  /* USER CODE BEGIN TIM1_MspDeInit 1 */
 
  /* USER CODE END TIM1_MspDeInit 1 */
  }
 
}
 
/**
* @brief UART MSP Initialization
* This function configures the hardware resources used in this example
* @param huart: UART handle pointer
* @retval None
*/
void HAL_UART_MspInit(UART_HandleTypeDef* huart)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  if(huart->Instance==USART1)
  {
  /* USER CODE BEGIN USART1_MspInit 0 */
 
  /* USER CODE END USART1_MspInit 0 */
    /* Peripheral clock enable */
    __HAL_RCC_USART1_CLK_ENABLE();
  
    __HAL_RCC_GPIOA_CLK_ENABLE();
    /**USART1 GPIO Configuration    
    PA9     ------> USART1_TX
    PA10     ------> USART1_RX 
    */
    GPIO_InitStruct.Pin = GPIO_PIN_9|GPIO_PIN_10;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
  /* USER CODE BEGIN USART1_MspInit 1 */
 
  /* USER CODE END USART1_MspInit 1 */
  }
 
}
 
/**
* @brief UART MSP De-Initialization
* This function freeze the hardware resources used in this example
* @param huart: UART handle pointer
* @retval None
*/
void HAL_UART_MspDeInit(UART_HandleTypeDef* huart)
{
  if(huart->Instance==USART1)
  {
  /* USER CODE BEGIN USART1_MspDeInit 0 */
 
  /* USER CODE END USART1_MspDeInit 0 */
    /* Peripheral clock disable */
    __HAL_RCC_USART1_CLK_DISABLE();
  
    /**USART1 GPIO Configuration    
    PA9     ------> USART1_TX
    PA10     ------> USART1_RX 
    */
    HAL_GPIO_DeInit(GPIOA, GPIO_PIN_9|GPIO_PIN_10);
 
  /* USER CODE BEGIN USART1_MspDeInit 1 */
 
  /* USER CODE END USART1_MspDeInit 1 */
  }
 
}
 
/* USER CODE BEGIN 1 */
 
/* USER CODE END 1 */

waclawek.jan · ‎2020-08-04

I don't understand. Do you see identical waveforms where exactly? Did you try a minimal program, with only one I2C? Did you try wiggling the pins manually? What board is this?

JW

CGrov.1 · ‎2020-08-05

The waveform on SCL-1 is identical to the waveform on SDA-1, and the waveform on SCL-3 is identical to the waveform of SDA-3. I have tried with only one I2C, with no change. The chip i am using is the STM32L476, it is mounted on a custom PCB for my project, I have ensured it is properly mounted with good contacts. I am going to try setting some of the I2C pins as GPIO outputs and run a quick script to see if it will toggle, just to double check the pin itself is still working.