• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 79 subscribers
  • Views 1246 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MSP430 PWM 1HZ

Mark Huang
Prodigy 60 points


Please help me with the code QQ

i am now suffering from the draining of my brain @@

How can i generate exactly a PWM signal with exactly "1 HZ"

here' s the already finished code:

WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
DCOCTL = 0; // Select lowest DCOx and MODx
BCSCTL1 = CALBC1_8MHZ; // Set range
DCOCTL = CALDCO_8MHZ; // Set DCO step + modulation

/*** GPIO Set-Up ***/
P1DIR |= BIT2; // P1.2 set as output
P1SEL |= BIT2; // P1.2 selected Timer0_A Out1

/*** Timer0_A Set-Up ***/

TA0CCR0 |= 1000-1; // PWM Period
TA0CCTL1 |= OUTMOD_7; // TA1CCR1 output mode = set/Reset
TA0CCR1 |= 250-1;
TA0CTL |= TASSEL_2 + MC_1; // SMCLK, Up Mode (Counts to TA1CCR0)




but i don't how to generate the signal in "1HZ"
i am now using MSP430 G2553

  • 0
    Guru 74080 points

    Do you want 1Hz of frequency with 50% duty cycle? Or do you need a variable duty-cycle inside the 1Hz? If variable, what is the desired resolution of the PWM?

    Dennis

  • 0
    Guru 46710 points

    Mark Huang said:
    How can i generate exactly a PWM signal with exactly "1 HZ"

    Easy. Using formula: PWM_frequency = timer_clock_frequency/(PWM_period_count-1).

    In your case it would be timer running from watch crystal (fork) oscillator, 32768Hz and TA0CCR0 = (32768 -1);

    Mark Huang said:
    TA0CCR0 |= 1000-1; // PWM Period

    This is totally wrong assignment that could lead to register contents which is not desired 999.

    You shall be using "="  operand, not "|=". Actually all your timer setup lines have same error.

  • 0 in reply to Ilmars
    Guru 74080 points

    Ilmars said:
    In your case it would be timer running from watch crystal (fork) oscillator, 32768Hz and TA0CCR0 = (32768 -1);

    This will be the best choice.

    If you do not have a watch crystal available in your application, you can also use an ISR driven software method for this low frequency.

**Attention** This is a public forum