Electrical – How to disable timer on MSP430

msp430pwmtimer

I am new to the TI MSP430G2553. I would like to send a PWM signal like in this picture:

_{(Image source: Adafruit – Understanding Infrared Signals)}

However I can't do that, because I don't know how to stop (finish) the PWM signal.
Here is my PWM signal code:

void configTimer(void)  // this function sends infinite pwm signal when button is pressed  
{
TA1CCR0 = 26-1;                          // Period 
  TA1CCR1 = 13;                            // 50% dutycycle
  TA1CCTL1 |= OUTMOD_6;                    //  Reset/Set
  TA1CTL = TASSEL_1 + MC_1 + TACLR; 
}

I tried:

TA1CTL1=0;
TA1CTL = MC_0;
set default value of TA1CCR1 = 0, when button pressed set TA1CCR1 = 13; and later __delay_cycles(any number);

However they didn't work.

Thanks in advance.

Edit: My last try
Edit2: Edit: I think can't use my timer interrupt my counter is always 0.

define TIMER0_A1_VECTOR (8u * 2u) /* 0xFFF0 Timer0)A CC1, TA0 */

define TIMER0_A0_VECTOR (9u * 2u) /* 0xFFF2 Timer0_A CC0 */

This is definiton of timer0 vector. How should i write it in my code?

#include <msp430.h>

void startTimer(void);

unsigned char counter=0;

void start2Timer(void);

int main(void)
{
WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer
BCSCTL1 = CALBC1_1MHZ; // Set range
DCOCTL = CALDCO_1MHZ; 
CCTL0 = CCIE; 

P2DIR |= BIT2;
P2SEL |= BIT2;// Select pwm  pin (transmitter)
       
P2OUT=0x00;


while(1){

if((P1IN & BIT4)!=BIT4) //button is pressed
  {
 startTimer(); 
 start2Timer();
  }
  
}

}

void startTimer(void) // pwm signal
{
TA1CCR0 = 26-1;                          // Period Register
  TA1CCR1 = 13;                            // TA1.1 25% dutycycle
  TA1CCTL1 |= OUTMOD_6;                    // TA1CCR1, Reset/Set
  TA1CTL = TASSEL_1 + MC_1 + TACLR;
}


void start2Timer(void) // trying to stop after 50 ms
{
CCR0 = 5000; // CCR0 5 ms 
TACTL = TASSEL_2 + MC_2; // 
}

#pragma vector=TIMER0_A0_VECTOR // Timer0_A0 
__interrupt void Timer_A (void)
{
if(++counter==10){ // is counter 10 (5*10=ms)
 TA1CCR1 = 0;   ; // Stop pwm 
counter = 0;
} 
}

Best Answer

You could do this to turn off the timer:

TA1CTL &= ~(MC_1) ;//or whatever mode the timer is running at

Related Solutions

Electronic – Timer overflow on MSP430

Not sure exactly which series MSP you're using so you'll have to look up the specifics. But the basic premise should apply across the board I think.

The following example is from the file msp430g2xx1_ta_03.c in the code snippets that can be downloaded from the TI Wiki:

#include <msp430.h>

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P1DIR |= 0x01;                            // P1.0 output
  TACTL = TASSEL_2 + MC_2 + TAIE;           // SMCLK, contmode, interrupt

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

// Timer_A3 Interrupt Vector (TAIV) handler
#pragma vector=TIMERA1_VECTOR
__interrupt void Timer_A(void)
{
 switch( TAIV )
 {
   case  2: break;                          // CCR1 not used
   case  4: break;                          // CCR2 not used
   case 10: P1OUT ^= 0x01;                  // overflow
            break;
 }
}

The key is checking the TAIV register to see what caused the interrupt. Take a look at page 416 of the CC430 Family User's Guide:

TAIV Register Description

Now the code example is looking for a value of 10 in the TAIV register and the User Guide indicates that 0x0E is the overflow. So, again, check your specific chip's documentation. But the TAIV register is what will tell you what the cause of the interrupt is.

Electronic – Using external oscillator for MSP430 Timer

To use an external 32.768 KHz crystal with the MSP430G2553, the crystal needs to be soldered between the Xin and Xout pins of the microcontroller. In the DIP package, those are pins 18 and 19. No additional components are required for this.

TA0CLK has nothing to do with this crystal's connection, please see the pin descriptions in the datasheet.

See this schematic of the MSP430 Launchpad Target Microcontroller section:

MSP430 Launchpad Target Board

You can see the two 0 Ohm resistors on the pins 18 and 19 - the crystal attaches between them.

Please note:

Adding a crystal prevents those pins from being used as GPIO Pin 2.6 / TimerA TA0.1 (the Xin pin's other functions) and GPIO Pin 2.7 (the Xout pin's other function.
Instead of crystal, a digital clock from an oscillator can also be supplied to Xin in bypass mode.
For crystals of frequency higher than the 32.768 KHz crystal, appropriately sized load capacitors are required in addition. See the relevant part-specific datasheet for this.

UPDATE:

Once the 32.768 KHz watch crystal is connected to the MSP430, the following notes are handy to confirm that the crystal is operational, and of course to use the crystal going forward.

The crystal on XIN / XOUT is used as ACLK. Conversely, for using ACLK, a crystal must be connected between XIN and XOUT.
If the implementation is on an MSP430 Launchpad board, note that crystal diagnostic code is provided in Justin's Tech Blog - the gold standard that pretty much everyone followed in the early days of the Launchpad.
Other such walk-throughs are in NJC's Launchpad Blog, and in the TI "Getting Started with the MSP430 Launchpad" document, in the "Optional Lab Exercise – Crystal Oscillator" section.
The internal (on-chip) matching capacitance needs to be set for the crystal to work: Set BCSCTL3 (Basic Clock System Control 3), BCSCTL3 |= XCAP_3; for the 12.5 pF watch crystal provided with the Launchpad.
Detailed information on using Low Frequency Crystals is provided in this TI document.
An excellent, step by step explanation and verification code is provided in this blog.
Most important: Code using LF crystal ACLK does not function as expected while stepping through in debug mode, you have to run the code in "Run" mode for the various diagnostic code fragments mentioned above to work. This quirk is apparently not documented anywhere, I spent a fair bit of time removing and resoldering the crystal on my first launchpad, assuming a failure, till I figured this out.