Fade Green LED on EZ430-RF2500 (MSP430F2274)

 Hi Tobias, the code has some itrinsic issues, the first chunk cannot set P1.1, TA0 just set port if timer overflow or compare act, if you select up count to a vale T0 is the final value and interrupt is fired when count reach the limit. Again interrupt fire at regular interval TAclock/TACCR0.

 You can obtain a pwm modulation but on TA1 and the other but not from TA0 so no chance to use hardware PWM

Tobias Vitzethum said:

    WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
 
    P1DIR |= BIT1                          // green LED P1.1 as output
    P1SEL |= BIT1;                                                    // P1.1 as TA0 Option
 

 Second chunk is more complex than needed, you are using two timer and TA1 is in some way trying to set PWM, this can be wrong, a single timer with a simple software counter can suffice:

Tobias Vitzethum said:

// Timer A0 interrupt service routine
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A0(void)
{
  //TACCR0 += 200;                            // Dieser Vektor nur für TACCR0 // Add Offset to TACCR0
}

#define MAX_PWM 100

volatile int pwm=0;

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                     // Stop WDT
  P1SEL = ~BIT1;                            // P1.1 (Green LED) as I/O Port
  P1DIR = BIT1;                                    // P1.1 as output
  TACCTL0 = OUTMOD_3 + CCIE /* CCIE == CCIFG*/;    // OUTMOD_3 = Set/Reset, OUTMOD_4 = Toggle; interrupt enabled
  TACTL = TASSEL_2 +  MC_1 + TAIE + ID_3;              // SMCLK, MC_1 = Upmode, MC_2 = Contmode, int enabled // ID_3 = Teiler 8

  __bis_SR_register(/*LPM0_bits + */GIE);       // Enter LPM0 w/ interrupt

  for(int i=MAX_PWM;i>0;i--)

  {

    pwm=i;

    __delaycycles(1000);

  }

  // your code here...
}

// Timer A0 interrupt service routine
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A0(void)
{

   static int pwmctr=0;
   TACCR0 += 200;                     // Dieser Vektor nur für TACCR0 // Add Offset to TACCR0

  if(pwmctr>pwm)

   P1OUT&=~BIT1;   // led off

 else

   P1OUT|=BIT1;   // led on

  if(++pwmctr>MAX_PWM)

     pwmctr=0;

}

 Tell me if this can be of help

Hello Roberto. Thank you for your answer!

Sorry for my late reply, I had exams.

Your source code unfortunately does not work, but I
think is goes in another way.

What I want to do is, to config a timer, by which I get
the first interrupt if the first value reches, and a second
interrupt if the timer has expired. And this, the whole time.
(Later, the LED should fade on and off the whole time.)

For a first test, there is a fix pwm set.

I've spend a couple of hours, tries so much and I can't
understand where the mistake is. I think it's just a
trifle, but i can't find it! Possibly I need additionally
the TACCTL1 register or the TIMERA0_VECTOR interrupt???

If everbody can tell me where the mistake is, I would be
very happy!!

Here is my code (at the moment, the LED is doing nothing):


#include "msp430x22x4.h"

void main(void)
{

    WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT

    P1SEL = ~BIT1;                            // green LED P1.1 as I/O
    P1DIR = BIT1;                            // green LED P1.1 as output
    
     // Up-Mode: The timer repeatedly counts from zero to the value of TACCR0.
    TACTL = TASSEL_2 +  MC_1 + TAIE + ID_3;          // SMCLK, Up-Mode, int enabled, divider 8

    // Output is set by TACCR0 and reset by TACCR1
    TACCTL0 = OUTMOD_7 + CCIE;                // TACCR0 Reset/Set, interrupt enabled


    TACCR0 = 10000;    // Period
    TACCR1 = 5000;    // Off-Time

    __bis_SR_register(/*LPM0_bits + */GIE);       // Enter LPM0 w/ interrupt
    
    while(1)
    {
        // The rest of the source
    }

}

// Timer_A3 Interrupt Vector (TAIV) handler
#pragma vector=TIMERA1_VECTOR
__interrupt void Timer_A1(void)
{

    switch (TAIV)        // Efficient switch-implementation
    {
        case 2:     P1OUT = ~BIT1;                // EQU1=TACCR1 is reached -> LED off
                    break;
        case 10:     P1OUT = BIT1;               // EQU0=TAIFG: Timer reaches TACCR0 -> LED on
                    break;
    }
}

Best regards

Tobias

Tobias Vitzethum said:

    P1SEL = ~BIT1;                            // green LED P1.1 as I/O

Tobias Vitzethum said:

    TACTL = TASSEL_2 +  MC_1 + TAIE + ID_3;          // SMCLK, Up-Mode, int enabled, divider 8

Tobias Vitzethum said:

    TACCTL0 = OUTMOD_7 + CCIE;                // TACCR0 Reset/Set, interrupt enabled

Tobias Vitzethum said:

    TACCR1 = 5000;    // Off-Time

I guess, you wanted to program OUTMOD_7 and CCIE for TACCTL1 isntead of TACCTL0.

However, why do you use an ISR (which has latency and also may be blocked if another ISR is running or GIE is clear) to toggle the pin? OUTMOD_7 will do so for you, if you set P1SEL.4

Jens-Michael Gross said:

I guess, you wanted to program OUTMOD_7 and CCIE for TACCTL1 isntead of TACCTL0.

However, why do you use an ISR (which has latency and also may be blocked if another ISR is running or GIE is clear) to toggle the pin? OUTMOD_7 will do so for you, if you set P1SEL.4

Hi Jens, from original question P1.1 has no timer set/reset on compare capability, fading led has no issue on latence of interrupt and I use frequently to dim Led and generate some low frequency PWM.

 Why not use P1.4? Led on Launchpad  are connected to P1.1 and P1.6.

 I cannot understand why my code wasn't working, but for now I avoid add more burden to.

 Edit.. sorry I realized now this is a code to be used on RF-2500, I come back after easter and I retry with code to see what is wrong.

Roberto Romano said:

original question P1.1 has no timer set/reset on compare capability,

Hallo Roberto, hallo Jens,

my program is still not working.
As you both noticed, the source Code is for the EZ430-RF2500.
I need the software pwm, because the green LED is unfortunally
connected to Pin 1.1.
For begin, I want only a software pwm by which I can change
the Duty Cycle by a register.
I still dont's know, why my code from my third post doesn't
work.

Have everybody an idea?

I would be very happy!

Tobias