MSP-EXP430FR6989: How to create Capture Interrupt for this device

Mehmet Cagri Kose

Part Number: MSP-EXP430FR6989

I am trying to develop a program to read DHT-11 sensor from the bottom up. For this reason, I need to use Timer in capture mode.

1. P1.3 is selected for capture input. I want to capture on the falling edges. But I could not create interrupt when I was trying by simply connecting 3.3 V to P1.3 then deconnecting. What might be wrong here? Maybe I misunderstand some aspect of the timers.

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

  P1SEL1 |= BIT3;     // 10 for secondary role
  P1SEL0 &= ~BIT3;
  P1DIR &= ~BIT3;

  PM5CTL0 &= ~LOCKLPM5;

  TA1CTL |= MC__STOP;
  TA1CCTL2 = CM_2 | CCIS_0 | CAP | CCIE | SCS; 
  TA1CTL = TASSEL__SMCLK | MC__CONTINUOUS;
  
  __enable_interrupt();
  
  while(1);
}

#pragma vector = TIMER1_A1_VECTOR
__interrupt void Timer_A1(void){
    __no_operation();
}

Thanks in advance.

over 4 years ago

0 David Schultz over 4 years ago

Guru 24885 points

You have to enable global interrupts. In addition, you say you apply 3.3V and then disconnect. What ensures that the voltage drops to zero after you disconnect?

0 Mehmet Cagri Kose over 4 years ago in reply to David Schultz

Intellectual 405 points

Yeah, I forgot to include global interrupt enable in my example code here. Real code is longer but I all commented out unnecessary parts. So the real code is effectively like above(with global interrupts enabled, I updated example above).

To your second question, I measure voltage on P1.3 with multimeter and shorted to ground just to be sure about voltage drop. It did not work-fire the interrupt.