Stm32L151RCxxx USART Hang issue, Interrupt Based TX/RX simultaneously - c

Question

I am running USART3, on 921600 BaudRate, using RTS CTS, I am always facing system hang when I try to do RX and TX simultaneously. I have pasted the main and IRQ code. IRQ is designed to Transmit a char 'A' while dropping all received data. Hangs happens when we disable USART_ITConfig(USART3, USART_IT_TXE, DISABLE);
Uart_Configuration()...
USART_ClockInitStructure.USART_Clock = USART_Clock_Disable;
USART_ClockInitStructure.USART_CPOL = USART_CPOL_Low;
USART_ClockInitStructure.USART_CPHA = USART_CPHA_2Edge;
USART_ClockInitStructure.USART_LastBit = USART_LastBit_Disable;
USART_ClockInit(USART3, &USART_ClockInitStructure);
USART_InitStructure.USART_Mode = (USART_Mode_Tx|USART_Mode_Rx);
USART_InitStructure.USART_BaudRate = u32BaudRate;
USART_OverSampling8Cmd(USART3, DISABLE);
USART_InitStructure.USART_Parity = USART_Parity_No ;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_RTS_CTS;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_Init(USART3, &USART_InitStructure);
USART_ITConfig(USART3,USART_IT_TXE, DISABLE);
USART_ITConfig(USART3, USART_IT_RXNE, ENABLE);
USART_Cmd(USART3, ENABLE);
Main.c ...
uint8_t UART_TransmitData(void)
{
if(u8IntTxFlag==1)
{
u8IntTxFlag=0;
USART_ITConfig(USART3, USART_IT_TXE, ENABLE);
return TRUE;
}
return FALSE;
}
void USART3_IRQHandler(void)
{
/* Implemented full duplex serial communication */
/* UART RX */
if(USART_GetITStatus(USART3, USART_IT_RXNE) != RESET)
{
USART_ReceiveData(USART3);
}
/* UART TX */
if(USART_GetITStatus(USART3, USART_IT_TXE) != RESET)
{
if(USART_GetFlagStatus(USART3, USART_FLAG_CTS) == RESET)
{
while(USART_GetFlagStatus(USART3, USART_FLAG_TXE) == RESET);
USART_SendData(USART3, 'A');
while(USART_GetFlagStatus(USART3, USART_FLAG_TC) == RESET);
USART_ClearFlag(USART3, USART_FLAG_TC);
USART_ITConfig(USART3, USART_IT_TXE, DISABLE);
u8IntTxFlag=1;
}
else
{
USART_ClearFlag(USART3, USART_FLAG_CTS);
}
}
}
int main(void)
{
RCC_ClocksTypeDef RCC_Clocks;
RCC_Configuration();
RCC_GetClocksFreq(&RCC_Clocks);
SysTick_Config(RCC_Clocks.HCLK_Frequency / 2000);
NVIC_Configuration();
Init_GPIOs();
SerialUARTConfig(921600, 0, 1, 8, 1);
while(1)
{
UART_TransmitData();
f_SleepMs(5);
}
return 0;
}

Answer 1

Maybe the USART_IT_TXE interrupt happens before you disable it? So the "Tx empty" interrupt pending flag is already set and there is no procedure inside your IRQHandler to clear that flag.