UART in MSP430 comunication doesn't work properly

[scorrpeio]

UART in MSP430

Hello,

I am writing a UART code to communicate with PC.

#include  "msp430x23x0.h"

void main(void)
{

  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  if (CALBC1_1MHZ ==0xFF || CALDCO_1MHZ == 0xFF)                                     
  {  
    while(1);                               // If calibration constants erased
                                            // do not load, trap CPU!!
  }   
 // BCSCTL1   = CALBC1_1MHZ;                  // Set DCO
 // DCOCTL    = CALDCO_1MHZ;
  
  P3SEL     = 0x30;                         // P3.4,5 = USCI_A0 TXD/RXD
  UCA0CTL1 |= UCSSEL_2;                     // SMCLK
  UCA0BR0   = 0x84;                         // 3.39 MHz 2400
  UCA0BR1   = 0x05;                         // 3.39 MHz 2400
  UCA0MCTL  = UCBRS2 + UCBRS0;              // Modulation UCBRSx = 5
  //UCA0CTL0   = 0x00;
  UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**
  IE2 |= UCA0RXIE;                          // Enable USCI_A0 RX interrupt
 // IE2 |= UCA0TXIE;                        // Enable USCI_A0 TX interrupt

  __bis_SR_register(LPM0_bits + GIE);       // Enter LPM0, interrupts enabled
  while(1)
  {
      
  }
}

// Echo back RXed character, confirm TX buffer is ready first
#pragma vector=USCIAB0RX_VECTOR
__interrupt void USCI0RX_ISR(void)
{
  while (!(IFG2&UCA0TXIFG));                // USCI_A0 TX buffer ready?
  UCA0TXBUF = UCA0RXBUF;                    // TX -> RXed character
 
}

This code is working but not properly.

When I press any key on keyboard...........I get random chars like α, √ etc........

I have used 2400 8-N-1 setting for UART communication.

Kindly let me know whats the problem.

 

[doraemon]

Re: UART in MSP430

Hello!

So it means you have an MSP430 with a serial port chip,
for instance MAX3232, and you try to send data with the PC, right?

Just in case: can you check that:
- The bitrate you set (apparently 2400) is also the same on the PC.
- Check the SMClock with a scope to check that it's really the value you
intended to use. There is something unclear: why do you check the
DCO calibration values if you use a 3.39 MHz crystal?
Basically in your code, you don't set any frequency, you just check
the calibration values. So the frequency should be the default DCO.
This means around 1 MHz. So the fastest way to get a start: output
SMCLOCK on one pin (check the data sheet for your device). Then
adapt the UCBRs accordingly.

Another thing: did you check TI's sample codes? I am sure there are
programs pretty close to what you want to do.

Dora.

 

[bobcat1]

Re: UART in MSP430

HI

Set the DCO to 1.8430 Mhz Or 3.6864MHz Insted of 3.9Mhz

See TI C code for doing so

All the best

Bobi

The microcontroller specialist

 

[scorrpeio]

Re: UART in MSP430

Hello!

So it means you have an MSP430 with a serial port chip,
for instance MAX3232, and you try to send data with the PC, right?

Just in case: can you check that:
- The bitrate you set (apparently 2400) is also the same on the PC.
- Check the SMClock with a scope to check that it's really the value you
intended to use. There is something unclear: why do you check the
DCO calibration values if you use a 3.39 MHz crystal?
Basically in your code, you don't set any frequency, you just check
the calibration values. So the frequency should be the default DCO.
This means around 1 MHz. So the fastest way to get a start: output
SMCLOCK on one pin (check the data sheet for your device). Then
adapt the UCBRs accordingly.

Another thing: did you check TI's sample codes? I am sure there are
programs pretty close to what you want to do.

Dora.

Thank you..........
Yes the freq is 1MHz as u said........
its working fine now