Phantom external interrupt issue with STM32F469AI (custom board)

Antypas.Peter · ‎2019-09-24

I am witnessing interrupts on EXTI9_5 line which have absolutely no electrical stimulus. I'm seeing this behavior consistently on multiple chips so this isn't a one-off.

The GPIO in question (ONE_WIRE_PIN) is PA8.

GPIO initialization here:

mIRQConfig.Pin   = ONE_WIRE_PIN;
  mIRQConfig.Mode  = GPIO_MODE_IT_FALLING;
  mIRQConfig.Pull  = GPIO_NOPULL;
  mIRQConfig.Speed = GPIO_SPEED_FREQ_HIGH;
  HAL_GPIO_Init(ONE_WIRE_PORT, &mIRQConfig);

Here is the interrupt routine:

void EXTI9_5_IRQHandler(void)
  {
    if ( EXTI->PR & ONE_WIRE_PIN )
      {
        HAL_GPIO_EXTI_IRQHandler(ONE_WIRE_PIN);
      }
    else if ( EXTI->PR & POWER_INT_PIN )
      {
        HAL_GPIO_EXTI_IRQHandler(POWER_INT_PIN);
      }
    else if ( EXTI->PR & TOUCH_INT_PIN )
      {
        HAL_GPIO_EXTI_IRQHandler(TOUCH_INT_PIN);
      }
  }

The HAL_GPIO_EXTI_IRQHandler is the vanilla implementation in the HAL:

void HAL_GPIO_EXTI_IRQHandler(uint16_t GPIO_Pin)
{
  /* EXTI line interrupt detected */
  if(__HAL_GPIO_EXTI_GET_IT(GPIO_Pin) != RESET)
  {
    __HAL_GPIO_EXTI_CLEAR_IT(GPIO_Pin);
    HAL_GPIO_EXTI_Callback(GPIO_Pin);
  }
}

And my callback is:

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
  {
    switch(GPIO_Pin)
    {
      case TOUCH_INT_PIN:
        {
          ewd1020_touch_int();
        }
        break;
      case POWER_INT_PIN:
        {
          max17043_clear_alert();
        }
        break;
      case ONE_WIRE_PIN:
        {
          singleWireSerialFallingEdge();
        }
        break;
    }
  }

The oscilloscope shows a constant voltage of 1.8V on that pin (VCC), with no falling edge triggering. Pullup resistor is external. Clearly, there is no electrical cause for this interrupt.

The interrupts occur as soon as USART2 becomes active. This is 100% repeatable and reproducible.

What could possibly be causing this? I've been working on this processor for 3 years now and I've seen my share of weirdness, but this takes the cake. Is there any HAL bug or misconfiguration that is even capable of exhibiting this behavior?

UPDATE:

One possible explanation for this problem might be a corruption of the interrupt vector. This is defined below. What would be a good way to validate the integrity of the vector at run time?

The OS is FreeRTOS 9.

__attribute__ ((section(".isr_vectors"), used))
void (* const g_pfnVectors[])(void) = {
    (void (*)(void))((unsigned long)&__stack_end__),
    ResetISR,
    NMI_Handler,
    HardFault_Handler,
    MemManage_Handler,
    BusFault_Handler,
    UsageFault_Handler,
    (void (*)(void))((unsigned long)&__valid_user_code_checksum),
    Unexpected_Handler,
    Unexpected_Handler,
    Unexpected_Handler,
    SVC_Handler,
    DebugMon_Handler,
    Unexpected_Handler,
    PendSV_Handler,
    SysTick_Handler,
    WWDG_IRQHandler,  // Window WatchDog                                        
    PVD_IRQHandler,  // PVD through EXTI Line detection                        
    TAMP_STAMP_IRQHandler,  // Tamper and TimeStamps through the EXTI line            
    RTC_WKUP_IRQHandler,  // RTC Wakeup through the EXTI line                       
    FLASH_IRQHandler,  // FLASH                                           
    RCC_IRQHandler,  // RCC                                             
    EXTI0_IRQHandler,  // EXTI Line0                                             
    EXTI1_IRQHandler,  // EXTI Line1                                             
    EXTI2_IRQHandler,  // EXTI Line2                                             
    EXTI3_IRQHandler,  // EXTI Line3                                             
    EXTI4_IRQHandler,  // EXTI Line4                                             
    DMA1_Stream0_IRQHandler,  // DMA1 Stream 0                                   
    DMA1_Stream1_IRQHandler,  // DMA1 Stream 1                                   
    DMA1_Stream2_IRQHandler,  // DMA1 Stream 2                                   
    DMA1_Stream3_IRQHandler,  // DMA1 Stream 3                                   
    DMA1_Stream4_IRQHandler,  // DMA1 Stream 4                                   
    DMA1_Stream5_IRQHandler,  // DMA1 Stream 5                                   
    DMA1_Stream6_IRQHandler,  // DMA1 Stream 6                                   
    ADC_IRQHandler,  // ADC1, ADC2 and ADC3s                            
    CAN1_TX_IRQHandler,  // CAN1 TX                                                
    CAN1_RX0_IRQHandler,  // CAN1 RX0                                               
    CAN1_RX1_IRQHandler,  // CAN1 RX1                                               
    CAN1_SCE_IRQHandler,  // CAN1 SCE                                               
    EXTI9_5_IRQHandler,  // External Line[9:5]s                                    
    TIM1_BRK_TIM9_IRQHandler,  // TIM1 Break and TIM9                   
    TIM1_UP_TIM10_IRQHandler,  // TIM1 Update and TIM10                 
    TIM1_TRG_COM_TIM11_IRQHandler,  // TIM1 Trigger and Commutation and TIM11
    TIM1_CC_IRQHandler,  // TIM1 Capture Compare                                   
    TIM2_IRQHandler,  // TIM2                                            
    TIM3_IRQHandler,  // TIM3                                            
    TIM4_IRQHandler,  // TIM4                                            
    I2C1_EV_IRQHandler,  // I2C1 Event                                             
    I2C1_ER_IRQHandler,  // I2C1 Error                                             
    I2C2_EV_IRQHandler,  // I2C2 Event                                             
    I2C2_ER_IRQHandler,  // I2C2 Error                                               
    SPI1_IRQHandler,  // SPI1                                            
    SPI2_IRQHandler,  // SPI2                                            
    USART1_IRQHandler,  // USART1                                          
    USART2_IRQHandler,  // USART2                                          
    USART3_IRQHandler,  // USART3                                          
    EXTI15_10_IRQHandler,  // External Line[15:10]s                                  
    RTC_Alarm_IRQHandler,  // RTC Alarm (A and B) through EXTI Line                  
    OTG_FS_WKUP_IRQHandler,  // USB OTG FS Wakeup through EXTI line                        
    TIM8_BRK_TIM12_IRQHandler,  // TIM8 Break and TIM12                  
    TIM8_UP_TIM13_IRQHandler,  // TIM8 Update and TIM13                 
    TIM8_TRG_COM_TIM14_IRQHandler,  // TIM8 Trigger and Commutation and TIM14
    TIM8_CC_IRQHandler,  // TIM8 Capture Compare                                   
    DMA1_Stream7_IRQHandler,  // DMA1 Stream7                                           
    FMC_IRQHandler,  // FMC                                            
    SDIO_IRQHandler,  // SDIO                                            
    TIM5_IRQHandler,  // TIM5                                            
    SPI3_IRQHandler,  // SPI3                                            
    UART4_IRQHandler,  // UART4                                           
    UART5_IRQHandler,  // UART5                                           
    TIM6_DAC_IRQHandler,  // TIM6 and DAC1&2 underrun errors                   
    TIM7_IRQHandler,  // TIM7                   
    DMA2_Stream0_IRQHandler,  // DMA2 Stream 0                                   
    DMA2_Stream1_IRQHandler,  // DMA2 Stream 1                                   
    DMA2_Stream2_IRQHandler,  // DMA2 Stream 2                                   
    DMA2_Stream3_IRQHandler,  // DMA2 Stream 3                                   
    DMA2_Stream4_IRQHandler,  // DMA2 Stream 4                                   
    ETH_IRQHandler,  // Ethernet                                        
    ETH_WKUP_IRQHandler,  // Ethernet Wakeup through EXTI line                      
    CAN2_TX_IRQHandler,  // CAN2 TX                                                
    CAN2_RX0_IRQHandler,  // CAN2 RX0                                               
    CAN2_RX1_IRQHandler,  // CAN2 RX1                                               
    CAN2_SCE_IRQHandler,  // CAN2 SCE                                               
    OTG_FS_IRQHandler,  // USB OTG FS                                      
    DMA2_Stream5_IRQHandler,  // DMA2 Stream 5                                   
    DMA2_Stream6_IRQHandler,  // DMA2 Stream 6                                   
    DMA2_Stream7_IRQHandler,  // DMA2 Stream 7                                   
    USART6_IRQHandler,  // USART6                                           
    I2C3_EV_IRQHandler,  // I2C3 event                                             
    I2C3_ER_IRQHandler,  // I2C3 error                                             
    OTG_HS_EP1_OUT_IRQHandler,  // USB OTG HS End Point 1 Out                      
    OTG_HS_EP1_IN_IRQHandler,  // USB OTG HS End Point 1 In                       
    OTG_HS_WKUP_IRQHandler,  // USB OTG HS Wakeup through EXTI                         
    OTG_HS_IRQHandler,  // USB OTG HS                                      
    DCMI_IRQHandler,  // DCMI                                            
    CRYP_IRQHandler,  // CRYP crypto                                     
    HASH_RNG_IRQHandler,  // Hash and Rng
    FPU_IRQHandler,  // FPU
    UART7_IRQHandler,  // UART7
    UART8_IRQHandler,  // UART8
    SPI4_IRQHandler,  // SPI4
    SPI5_IRQHandler,  // SPI5
    SPI6_IRQHandler,  // SPI6
    SAI1_IRQHandler,  // SAI1
    LTDC_IRQHandler,  // LTDC
    LTDC_ER_IRQHandler,  // LTDC error
    DMA2D_IRQHandler,  // DMA2D
    QUADSPI_IRQHandler,  // QUADSPI
    DSI_IRQHandler,  // DSI
};

waclawek.jan · ‎2019-09-24

> absolutely no electrical stimulus

Connect it directly to GND to be sure.

JW

Antypas.Peter · ‎2019-09-25

Grounding defeats it. But it's supposed to be a falling edge and the scope doesn't detect anything. I've set the threshold to 1.72V with a VCC of 1.8V and it's not triggering on the scope, so why would it trigger inside the GPIO?

waclawek.jan · ‎2019-09-27

Maybe because your scope+probe+grounding arrangement is not fast enough to capture short spikes the EXTI pin sees.

JW

Antypas.Peter · ‎2019-09-27

Switching from PA8 to PB14 resolved the issue. This will remain a mystery for now.