alternating pwm on msp430g2231

You said:"CCTL0 does not work properly". In what way?

Is that in the Errata? Or, did you find an UN-documented bug?

I meant I cannot use it to toggle the outputs of any of the ports. and with the use of CCTL1 I am able to toggle only the ports1.2 and 1.6 but not in an alternating manner. Does anyone have the code for this?.

Pritam Kalaimani said:

I meant I cannot use it to toggle the outputs of any of the ports. and with the use of CCTL1 I am able to toggle only the ports1.2 and 1.6 but not in an alternating manner. Does anyone have the code for this?.

You can also toggle port 1.1 and/or 1.5 in addition to what you did with port 1.2 and/or 1.6. You can make 1.1 and/or 1.5 to have a different phase (including but not limited to 180 degrees) as compared with that of 1.2 and/or 1.6.

Is that what you are after?

Hi 

Thank you for your reply. Yes that is pretty much what I am looking for. It would be great if u could post the method/code for getting the alternating PWM's from P1.1 and P1.5 . It would be very helpful.

Thanks.

#include <msp430.h>

void main(void)
{
  WDTCTL = WDTPW | WDTHOLD;
  P1SEL = BIT6 | BIT5 | BIT2 | BIT1;
  P1DIR = BIT6 | BIT5 | BIT2 | BIT1;

  TACCR0 = 999;            // period - 1
  TACCR1 = 999;            // same

  TACCTL0 = 0;             // initially low
  TACCTL1 = OUT;           // opposite

  TACCTL0 = OUTMOD_4;      // toggle
  TACCTL1 = OUTMOD_4;      // same

  TACTL = TASSEL_2 | MC_1; // up-mode

  while (1);
}

Hi 

Thank you so much for the code. It is working fine. I have another problem though. I need to have some control over the dead time. I find that by varying the value of TACCR1 the phase of the PWM's change. How do I control the dead time. Can u help me on this as well. Thanks in advance.

The Timer in G2231 cannot do that without CPU assists. If the toggle frequency is slow, CPU may be able to help.

What is the required toggle frequency?

well I need to initially generate the PWM's at 50KHz for a few seconds and then bring it down to 25KHz. .

@ old_cow_yellow

Thank you for all the help so far. but can you also please post on how to get control of the dead time. Please, its kinda urgent. 

#include <msp430.h>

void main(void)
{
  WDTCTL = WDTPW | WDTHOLD;

  P1SEL = BIT6 | BIT5;
  P1DIR = BIT6 | BIT5;
 
  TACCR0 = 10;
  TACCR1 = 10-1;

  TACCTL0 = OUTMOD_1 | CCIE;

  TACTL = TASSEL_2 | MC_2;

  __bis_SR_register(GIE);
    
  while (1);
}

#pragma vector = TIMERA0_VECTOR
__interrupt void Timer1_A0_ISR(void)
{
  TACCR0 += 99;
  TACCTL0 = OUTMOD_5;
  TACCR1 += 101;
  TACCTL1 = OUTMOD_1 | CCIE;
}

#pragma vector = TIMERA1_VECTOR
__interrupt void Timer1_A1_ISR(void)
{
  if(TAIV == 2)
  {
    TACCR1 += 99;
    TACCTL1 = OUTMOD_5;
    TACCR0 += 101;
    TACCTL0 = OUTMOD_1 | CCIE;
  }
}

Hi OCY

Thank you for your post. I am looking to achieve results something like the pictures that I have attached. In your program by varying what I will be able to achieve this. Also can you please give a brief explanation of your code. 

Thanks in advance.

Something like that can be done by using the time in up/down mode and use toggle/set and toggle/reset for the PWMs.

Example:
TAR=0 is at the middle line of your screenshot, TAR=CCR0= 100 is at the second one to the right.
Blue runs in toggle/reset mode, so it resets on TAR=0, gets toggled (on) on TAR = TACCR1 = 60, 80 ticks later, when counting down from 100, it is toggled again (off) on 60, and when the timer reaches 0 it is reset (stays off).

Yellow runs in toggle/set mode. It is set on TAR=0, gets toggled (off) on TAR = TACCR2 = 30, stays there for 70 ticks up and another r70 ticks down, gets toggled on again on 30 and stays set on 0. Exactly your signal (except for the absolute values)

On the first cycle, the outputs may be reversed (depending on the initial values), which is corrected on the next TAR->0. But you may as well initialize them manually (setting the OUT bit while in OUTMOD_0)

Pritam,

JMG’s method would work too. But my Apr 16 code is generating “something like the picture”. Both waveforms are 99 cycles high and 101 cycles low with a dead-band of 1 cycle between the two waveforms.

-- OCY

Hi OCY 

Thanks for your reply, this was a picture taken from that of a different microcontroller (MSP430g2553). However, the code that u have given also produces similar results but i'm not able to vary the frequency. Is it possible to post the code where varying the frequency will be possible. I would be really greatful.

Thanks in advance.

Regards

Pritam