Not Answered! Loop Back with RS422 --- I came to this point!

Also, I realized that I cannot have the following code if I want to have loop Back! Because, loopback cannot interrupt the TX and then ask for RX!

#pragma vector = USCIAB1RX_VECTOR
  __interrupt void ReceiveInterrupt(void)
  {
   
   UC1IFG &= ~UCA1RXIFG; // Clear RX flag 
   if (UCA1RXBUF == '1')
   {

     y++;
   }

Because the way I send from Hyper is totally different than from the Loopback!

However, I don't know what to use instead!

Then should I remove TXBUF from the interrupt then?

You want that the tx-uart to continuously to send '1'
once a char is transferred to the pipeline the txbuff is ready for another char it will generate a irq.

But you must see that the isr just sitting there by itself will not start this chain-reaction.

UC1IE |= UCA1TXIE; // Enable the Transmit interrupt
UC1IFG |= UCA1TXIFG; // trigger chain-reaction <<<<<<<<<

P.S this is not needed: UC1IFG &= ~UCA1RXIFG; // Clear RX flag 
Reading RXBUF clears it.

old_cow_yellow said:

I think the loop-back (line #13) was commented out and that is why it does not loop back.

No! We used the hardware loopback not the software one! That's why I commented out! We need to have the RX what we had sent through TX! But it does not!

Michael,

Thanks for your reply, I did the following changes. And like the previous time I have nothing. However, when I use my other device which has Loop back + battery power, sometimes I receive garbage!!! such as A with two dots on top and Y with two dots on top! (extended Ascii chart)

I believe that I do not have enough time to grab what I have sent through TX!

As you said my Simple loop back has only TX(+ to +) and RX(- to -) but in the battery powered the ground which is pin 5 is also considered!

That's why you talk about resistors and biasing! I guess the bias is now OK but my buffer is getting garbage!

Oh I see the baud rate, I did not check for that!  UCA1BR0!

Um..... I am getting closer I guess!

#include "msp430f47197.h"
int y;
void main(void)
{
   WDTCTL = WDTPW + WDTHOLD; // Stop the Watch dog
  
   P1SEL  |=  BIT6 + BIT7;  // P1.1 UCA1RXD/TXD input
  
   UCA1CTL1 |=  UCSSEL_2 + UCSWRST;  // USCI Clock = SMCLK,USCI_A0 disabled
   UCA1BR0   =  104;                 // 104 From datasheet table-  
   UCA1BR1   =  0;                   // -selects baudrate =9600,clk = SMCLK
   UCA1MCTL  =  UCBRS_1;             // Modulation value = 1 from datasheet
  // UCA0STAT |=  UCLISTEN;            // loop back mode enabled 
   UCA1CTL1 &= ~UCSWRST;             // Clear UCSWRST to enable USCI_A0
      
  //---------------- Enabling the interrupts ------------------//

 // UCA1TXBUF = 'B';
   
   UC1IE |= UCA1TXIE;                  // Enable the Transmit interrupt
   UC1IE |= UCA1RXIE;                  // Enable the Receive  interrupt
   _BIS_SR(GIE);                     // Enable the global interrupt
//    while (!(UC1IFG & UCA1TXIFG));       
  // UCA1TXBUF = 'A';                  // Transmit a byte 
//      __delay_cycles(1000);
   
   
   
   
   _BIS_SR(LPM0_bits + GIE);         // Going to LPM0
}

  //-----------------------------------------------------------------------//
  //                Transmit and Receive interrupts                        //
  //-----------------------------------------------------------------------//

  #pragma vector = USCIAB1TX_VECTOR
  __interrupt void TransmitInterrupt(void)
  {
    UCA1TXBUF  = '@';
   while (!(UC1IFG & UCB1TXIFG));
   UC1IE &= ~UCB1TXIE;
   UC1IFG &= ~UCB1TXIFG;
   __bic_SR_register_on_exit(LPM0_bits);
  }

  #pragma vector = USCIAB1RX_VECTOR
  __interrupt void ReceiveInterrupt(void)
  {
   
   UC1IFG &= ~UCA1RXIFG; // Clear RX flag 
   if (UCA1RXBUF == '@')
   {
//   goto TT; 
   y++;
    // __delay_cycles(1000);
   }
  }

This does not make sense to me!!!

I changed the code to the following and with playing the wire ( figure) I get those garbage!

#include "msp430f47197.h"
int y;
void main(void)
{
   WDTCTL = WDTPW + WDTHOLD; // Stop the Watch dog
  
   P1SEL  |=  BIT6 + BIT7;  // P1.1 UCA1RXD/TXD input
  
   UCA1CTL1 |=  UCSSEL_2 + UCSWRST;  // USCI Clock = SMCLK,USCI_A0 disabled
   UCA1BR0   =  104;                 // 104 From datasheet table-  
   UCA1BR1   =  0;                   // -selects baudrate =9600,clk = SMCLK
   UCA1MCTL  =  UCBRS_1;             // Modulation value = 1 from datasheet
   UCA1CTL1 &= ~UCSWRST;             // Clear UCSWRST to enable USCI_A0
      
  //---------------- Enabling the interrupts ------------------//


   
   UC1IE |= UCA1TXIE;                  // Enable the Transmit interrupt
   UC1IE |= UCA1RXIE;                  // Enable the Receive  interrupt
   _BIS_SR(GIE);                     // Enable the global interrupt

   
   while (1)
   {
     
     UCA1TXBUF  = '1'; 
 
   
   
     
  
   }
   
   
  
}

  //-----------------------------------------------------------------------//
  //                Transmit and Receive interrupts                        //
  //-----------------------------------------------------------------------//


  #pragma vector = USCIAB1RX_VECTOR
  __interrupt void ReceiveInterrupt(void)
  {
    UC1IFG &= ~UCA1RXIFG; // Clear RX flag 
   if (UCA1RXBUF == '1')
   {
     
     y++;
   } 
    
  }