Not receiving the UART RX interrupt

Kewal Deshpande35

Other Parts Discussed in Thread: MSP430G2955

I am using MSP430G2955 and I am unable to receive RX interrupt but I am able to see that RXBUF has been filled with the data sent from a host PC.

I have enabled the GIE and also the RXIE, so is there anything else which needs to be set.

#define TXLED BIT0
#define RXLED BIT1
#define TXD BIT5
#define RXD BIT4

const char SendString[] = { "Received 56 bytes of data\r\n" };
char RecString[56];
unsigned int nRecStringCount; // counter for bytes recevied
unsigned int nCount; //Counter



#pragma vector=USCIAB0RX_VECTOR
__interrupt void USCI0TX_ISR(void)
{
 //some stuffs here
}

#pragma vector=USCIAB0RX_VECTOR
__interrupt void USCI0RX_ISR(void)
{
   //Some stuffs here

}


int main(void) {
	WDTCTL = WDTPW | WDTHOLD;		// Stop watchdog timer

   DCOCTL = 0; // Select lowest DCOx and MODx settings
   BCSCTL1 = CALBC1_1MHZ; // Set DCO
   DCOCTL = CALDCO_1MHZ;

   P2DIR |= 0xFF; // All P2.x outputs
   P2OUT &= 0x00; // All P2.x reset


   P3SEL |= RXD + TXD ; // P1.1 = RXD, P1.2=TXD
   P3SEL2 |= RXD + TXD ; // P1.1 = RXD, P1.2=TXD
   P2DIR |= RXLED + TXLED;
   P2OUT &= 0x00;

   UCA0CTL0 |= UCPEN + UCPAR ; // for Even parity
   UCA0CTL1 |= UCSSEL_2 ; // 2 for SMCLKm, 1 for ACLK

   UCA0BR0 = 0x34; // 1MHz 19200
   UCA0BR1 = 0x00; // 1MHz 19200
   UCA0MCTL = UCBRS0 ;//+ UCBRS2; // Modulation UCBRSx = 5


   nRecStringCount = 0;

   UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**

   IE2 |= UCA0RXIE; // Enable USCI_A0 RX interrupt

   LPM0 + GIE; // Enter LPM0 w/ int until Byte RXed

   while (1)
   { }

}

Also to note that I have recieved that the data sent 0xAB from a remote PC to UART port of the controller.

over 10 years ago

0 Tony Philipsson over 10 years ago

Guru 12050 points

LPM0 + GIE; // Enter LPM0 w/ int until Byte RXed

what is that? unless CCS has some new macro thing I don't know, you need to use a type of __intrinsics like this

_BIS_SR(LPM0_bits + GIE); // Enter LPM0 w/ interrupt

0 Dennis Eichmann over 10 years ago

Guru 74080 points

Hi Kewal!

By the way: You have two RX ISRs defined

#pragma vector = USCIAB0RX_VECTOR
__interrupt void USCI0TX_ISR( void )
{
  // Some stuff here
}

#pragma vector = USCIAB0RX_VECTOR
__interrupt void USCI0RX_ISR( void )
{
  // Some stuff here
}

It is not your own name

__interrupt void USCI0TX_ISR( void )

that specifies the ISR, it is the #pragma

#pragma vector = USCIAB0RX_VECTOR

And if you successfully changed your code according to Tony's suggestion, you should do something in your ISR to set a breakpoint or add a NOP to see that your program is inside the ISR. Furthermore keep in mind that if you do not read the RX buffer or clear the bit manually after a received byte, the IFG stays set and the ISR is executed over and over again.

Dennis

0 Kewal Deshpande35 over 10 years ago in reply to Tony Philipsson

Intellectual 260 points

Hi Tony,

LPM0 is defined in the intrinsics as _BIS_SR(LPM0_bits );

Also,

I had another question releated to setting it to LPM0 ....I did search through few tutorials and questions but have been able to form a concrete idea on this.

So I have a while loop in main and also i need to set __BIS_SR(LPM0_bits + GIE);

Do i need to just put it to LPM0 mode and then call the while loop.

What I am trying to achieve is,... When some push button is pressed it sets a enable flag,. based on that enable flag the while loop would update some stuff and return back to LPM0 mode. so code would something like below, is it correct?




Main
{
//Initialize and configure


While(1)
 {
    if(updateflag updated)
   //Do something and toggle something


   //Go to low power mode
   __BIT_SR(LPM0 +GIE)
 }

//Never comes here end of app
}



__ISR 
Port pin ISR
{
 //Update flag

}

0 Clemens Ladisch over 10 years ago in reply to Kewal Deshpande35

Guru 318740 points

The interrupt handler has to wake up the main loop with something like __bic_SR_register_on_exit(LPM0_bits); otherwise, the CPU goes back to sleep as soon as the interrupt handler is finished.

This is explained in SLAA294.

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Not receiving the UART RX interrupt