Level control of 485 transceiver control angle of STM32 serial port

Regarding 485 level control, if the level conversion is performed directly after the transmission interrupt processing, the transmission data will be incomplete. If a certain delay is added and then the level conversion is performed, this problem can be solved, but it is a bit cumbersome. The solution is to enable the transmission completion interrupt: USART_IT_TC (Transmission complete interrupt) can achieve precise control. It should be noted that this interrupt will be generated before a byte is sent, so it is recommended to enable it after the last byte is loaded into the transmission buffer.

void USART1_IRQHandler(void)

{

CPU_INT08U rx_data;

CPU_INT08U tx_data;

    if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET) //Serial port 1 receiving process

    {       

rx_data = (USART_ReceiveData(USART1) & 0xFF);

// Put into channel 1 receive buffer circular queue

if (!COM_CHANNEL_RXByteIn(BSP_RTU_CHANNEL_NO1, rx_data)) 

{

 // Buffer is full, reception failed

}

    }    

    if(USART_GetITStatus(USART1, USART_IT_TXE) != RESET) //Serial port 1 sending process

    {       

if (COM_CHANNEL_TXByteOut(BSP_RTU_CHANNEL_NO1, &tx_data)) 

{

USART_SendData(USART1, tx_data);

  } 

  else 

  {

USART_ITConfig(USART1, USART_IT_TXE, DISABLE); //Disable transmit interrupt

USART_ClearITPendingBit(USART1,USART_IT_TC);

USART_ITConfig(USART1, USART_IT_TC, ENABLE);

}   

    }    

    if(USART_GetITStatus(USART1, USART_IT_TC) != RESET) //Serial port 1 sends and completes processing

    {       

USART_ITConfig(USART1, USART_IT_TC, DISABLE); //Disable transmit interrupt

GPIO_WriteBit(GPIOB, GPIO_Pin_5,Bit_RESET); //RX_ENABLE

    }    

}