STM32F4 Discovery, cannot clear parity error intterrupt

[takeda]

Posted on June 02, 2014 at 04:16

Hello,

I'm using STM32F4 discovery to develop usart communication function. The usart parameter is below.

 /// Set serial port

 USART_StructInit(&USART_InitStructure);  USART_InitStructure.USART_BaudRate = 9600;          ///< 9600bps  USART_InitStructure.USART_WordLength = USART_WordLength_9b;      ///< data 8bit + parity 1bit  USART_InitStructure.USART_StopBits = USART_StopBits_1;       ///< stop 1bit  USART_InitStructure.USART_Parity = USART_Parity_Even;       ///< parity even  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;     ///< enable Rx, Tx  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; ///< no hardware flow control  USART_Init(USART3, &USART_InitStructure); And enable PE interrupt, and then, send parity error data to this discovery board. So, parity error interrupt is occurred successfully, but after this parity error intterupt is occured continuously (I cannot clear the PE error bit). The USART intterrupt is below.

void USART3_IRQHandler (void) __irq

{      char tmpRcv;         /// PE Interrupt  (PE flag is cleared when the flag is read)       if (USART_GetFlagStatus(USART3, USART_FLAG_PE) == SET)          {      }

     /// RXNE interrupt

     else if (USART_GetFlagStatus(USART3, USART_FLAG_RXNE) == SET)      {           ///receive data (and the RXNE flag is cleared)           tmpRcv = USART_ReceiveData(USART3);         ....

     }

It seems that the PE flag is not cleared when the flag is read. Please help to solve this problem. best regards. #uart #stm32 #discovery #usart

[takeda]

Posted on June 02, 2014 at 06:03

Hello,

I modified the usart intterupt handler as below and it seems to work correct.

void USART3_IRQHandler (void) __irq

{      char tmpRcv;

     /// RXNE interrupt

     if (USART_GetFlagStatus(USART3, USART_FLAG_RXNE) == SET)     {           if (USART_GetFlagStatus(USART3, USART_FLAG_PE) != SET)          {                       ///receive data and clear RXNE interrupt flag                tmpRcv = USART_ReceiveData(USART3);          }          else         {                 tmpRcv = USART_ReceiveData(USART3);                USART_GetFlagStatus(USART3, USART_FLAG_PE);         }     } }

Is this sequence is correct ?

And, I think this code is not simple, if there are other better code, please let me know.

best regards.

[Tesla DeLorean]

Posted on June 02, 2014 at 06:06

The PE is NOT cleared by reading the status, but rather reading the data register.

[Tesla DeLorean]

Posted on June 02, 2014 at 06:22

#define USART_FLAG_ERRORS (USART_FLAG_ORE | USART_FLAG_NE | USART_FLAG_FE | USART_FLAG_PE)
void USART3_IRQHandler(void)
{
if (USART_GetFlagStatus(USART3, USART_FLAG_ERRORS) == SET) 
{
USART_ReceiveData(USART3); // Discarded read to clear
}
/// RXNE interrupt
if (USART_GetFlagStatus(USART3, USART_FLAG_RXNE) == SET)
{
char tmpRcv; 
///receive data (and the RXNE flag is cleared)
tmpRcv = USART_ReceiveData(USART3);
....
}
}