USART TX interrupt

[cgengineer]

Hello everyone,

can someone help me using the USART TX interrupt?
I can't understand how to initiate a TX streaming without using TXSTA.TRMT polling

Thank you
CG

[cgengineer]

Hi,

no one is using the usart tx interrupt?

I did a simple routine (a state machine) that avoids continuous polling of TXSTA.TRMT, for my modbus implementation, but is going to be heavier than a simple while waiting for trasmission to complete:
(I have a rs485 driver with tx and rx enables, I put the rx into standby when unused to save power)

Code: Select all

  typedef enum __TXStatus {
      TX_INIT,
      TX_WAIT,
      TX_ENABLED,
      TX_STOP


  } _TXStatus;
  unsigned char g_ucTXStatus = TX_INIT;
  
  void ModbusSerialTXBufferUnloadTask (void) {
      //scarica completamente il buffer di uscita
      //controlla se il buffer non è vuoto e fa il ritardo
      unsigned char ucONBitCounter = 0;
      unsigned char ucTemp;

      switch (g_ucTXStatus) {
      
          case TX_INIT:     if (FifoEmpty(&g_SerialTX))                                       break;
                            if (g_b_TMR3clock1mSSerialReplyCounter < MODBUS_RX_TO_TX_DELAY)   break;
                            //inizia la comunicazione
                            DOenRXua = 1;
                            Delay_us(1);
                            DOenTXua = 1;
                            Delay_us(1);
                            g_ucTXStatus = TX_ENABLED;
                            break;
          case TX_ENABLED:  if (FifoEmpty(&g_SerialTX)) {
                                g_ucTXStatus = TX_STOP;
                                break;
                            }
                            ucTemp = FifoPop(&g_SerialTX);
                            if (g_ucUARTParityType) {

                                if (ucTemp.F0) ucONBitCounter++;
                                if (ucTemp.F1) ucONBitCounter++;
                                if (ucTemp.F2) ucONBitCounter++;
                                if (ucTemp.F3) ucONBitCounter++;
                                if (ucTemp.F4) ucONBitCounter++;
                                if (ucTemp.F5) ucONBitCounter++;
                                if (ucTemp.F6) ucONBitCounter++;
                                if (ucTemp.F7) ucONBitCounter++;

                                switch (g_ucUARTParityType) {
                                    case ODD   : if (ucONBitCounter.F0)  TXSTA.TX9D = 1;               break;
                                    case EVEN  : if (!ucONBitCounter.F0) TXSTA.TX9D = 1;               break;
                                    case MARK  : TXSTA.TX9D = 1;                                       break;
                                    case SPACE : TXSTA.TX9D = 0;                                       break;
                                }
                            }
//                            UART1_Write(ucTemp);
                            TXREG1 = ucTemp;
                            
                            g_ucTXStatus = TX_WAIT;
                            break;
          case TX_WAIT:     if(!TXSTA.TRMT) break;
                            g_ucTXStatus = TX_ENABLED;
                            break;
          case TX_STOP:     DOenTXua = 0;
                            Delay_us(1);
                            DOenRXua = 0;
                            g_ucTXStatus = TX_INIT;
                            break;
          default:          g_ucTXStatus = TX_INIT;
                            break;
      }

  }

Really nobody can help me?

Thank you
CG

[filip.grujcic]

Hello,

What MCU are you using?
I advise you to consult the datasheet for your MCU, in order to learn how to use the TX interrupt.

Kind regards,

[cgengineer]

Hello,

What MCU are you using?
I advise you to consult the datasheet for your MCU, in order to learn how to use the TX interrupt.

Kind regards,

PIC18F67K22

thank you
Best
CG

[filip.grujcic]

Hello,

Could you please explain why and where exactly you are trying to implement a TX interrupt?
From the code you posted, I'm not sure I understand the problem fully.

Best regards,