MSP430F2274 UART RX Problem

Hi Vidushi!

If you want to poll for a received character, you simply have to poll for the RX interrupt flag:

uint8_t received_symbol;
...

if( IFG2 & UCA0RXIFG )
{
  received_symbol = UCA0RXBUF; // Copy received symbol - reading RX buffer clears IFG
}

...

Dennis

Hi

Thanks for your early response..

What we have to mention in UART_init?

I have mentioned

P3SEL = RXD + TXD;

UCA0CTL1 |= UCSSEL_2; // SMCLK
UCA0BR0 =104; // 1MHz 9600
UCA0BR1 = 0; // 1MHz 9600
UCA0MCTL = UCBRS0; // Modulation UCBRSx = 1
UCA0CTL1 &= ~UCSWRST; // Initialize USCI state machine

Yes, if you also have

BCSCTL1   = CALBC1_1MHZ;    // Set range
DCOCTL    = CALDCO_1MHZ;    // Set DCO step and modulation

at the beginning of your code, then everything looks fine. And disable or feed the watchdog, of course.

Dennis

Hi Dennis,


unable to get anything in UCA0RXBUF.

Please show your complete code.

Hi Dennis,


This is demo code i made please have a look to this..


void uart_putc(unsigned char c)
{
while(!(IFG2&UCA0TXIFG)); // USCI_A0 TX buffer ready?
UCA0TXBUF = c; // TX
//while(!(UCA0STAT&UCBUSY));
}

void uart_puts(const char *str)
{
while(*str)
{
uart_putc(*str++);
}
}

unsigned char uart_getc()
{
unsigned char received_symbol;
while(IFG2&UCA0RXIFG)
{
received_symbol = UCA0RXBUF; // Copy received symbol - reading RX buffer clears IFG
}

return received_symbol;
}
int main(void)
{
WDTCTL = WDTPW + WDTHOLD;
P1DIR = 0xFF; // All P1.x outputs
P1OUT = 0; // All P1.x reset
P2DIR = 0xFF; // All P2.x outputs
P2OUT = 0; // All P2.x reset
P3SEL = 0x30; // P3.4,5 = USCI_A0 TXD/RXD
P3DIR = 0xFF; // All P3.x outputs
P3OUT = 0; // All P3.x reset
P4DIR = 0xFF; // All P4.x outputs
P4OUT = 0; // All P4.x reset

// P3SEL = RXD + TXD;
UCA0CTL1 |= UCSSEL_2; // SMCLK
UCA0BR0 =104; // 1MHz 9600
UCA0BR1 = 0; // 1MHz 9600
UCA0MCTL = UCBRS0; // Modulation UCBRSx = 1
UCA0CTL1 &= ~UCSWRST; // Initialize USCI state machine
__bis_SR_register(LPM3_bits + GIE); // Enter LPM3, interrupts enabled

while(1)
{
while(1)
{
uart_putc(0x55);
uart_getc();
}
}
}

One thing I noticed at first sight:

while( IFG2&UCA0RXIFG )
{
  received_symbol = UCA0RXBUF; // Copy received symbol - reading RX buffer clears IFG
}

If you want to wait until something is inside the buffer, you have to write:

while( !(IFG2 & UCA0RXIFG) ); // Wait until a symbol was received
received_symbol = UCA0RXBUF;  // Copy received symbol - reading RX buffer clears IFG

I don't know if this is what you wanted to do?

Dennis

yes Wait until a symbol was received tried this also..

Dennis,

In uart_getc just waiting for symbol to be received at this line while( !(IFG2 & UCA0RXIFG) );

Thanks for early response