MSP430 TIMERA1 Interrupt [duplicate] - c

Question

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MSP430G2553 Timer Intervals [closed]
(3 answers)
Closed 6 years ago.
Quick question. How do I set an interrupt for 10 seconds and a minute with this specific interrupt? I have tried using the counter below but it does not work. As this program stands, it interrupts 1 second. I would usually go to the professor in times like these, however, he is in Japan.... .... ....
#include <msp430.h>
#define RedLED BIT0
#define GreenLED BIT6
#define RedLEDToggle (P1OUT ^= RedLED)
#define GreenLEDToggle (P1OUT ^= GreenLED)
unsigned int i = 0;
void main(void)
{
WDTCTL = WDTPW|WDTHOLD;
P1DIR = RedLED|GreenLED;
P1OUT = RedLED|GreenLED;
TACTL = TASSEL_2|ID_3|MC_3|TAIE;
TACCR0 = 62500;
_enable_interrupts();
LPM1;
}
#pragma vector=TIMER0_A1_VECTOR
__interrupt void Timer_A(void){
if (int i == 10)
{
switch(TAIV)
{
case 0x02: break;
case 0x04: break;
case 0x0A: RedLEDToggle|GreenLEDToggle;;
break;
}
}
else
{
i++;
}
}

Answer 1

To achieve 10 second interrupt interval, you need to apply input divider to the timer. It is not possible to achieve 1 minute without peripheral support (but you can implement that with a software counter).
The problem is that msp430 microcontrollers have 16-bit registers, not capable of holding numerical values larger than 65535. Using low-frequency oscillator running at 32768 Hz (as is typical - you don't provide any details about the hardware clock sources of your system, if they have a different frequency, please mention that) the register overflows once every 2 seconds unless an input divider is applied. The maximum value of input divider on MSP430x2xxx family MCUs is 8, so it's not possible to set a hardware timer more than 8 * 2 = 16 seconds in the future. Refer to MSP430x2xxx family user's guide for further details.
This code calls the interrupt once 10 seconds:
#include <msp430.h>
#define RedLED BIT0
#define GreenLED BIT6
#define RedLEDToggle (P1OUT ^= RedLED)
#define GreenLEDToggle (P1OUT ^= GreenLED)
// 10 seconds, assuming 32768 Hz ACLK source and divider 8
#define TIMER_PERIOD (10u * (32768 / 8))
void main(void)
{
WDTCTL = WDTPW | WDTHOLD;
P1DIR = RedLED | GreenLED;
P1OUT = RedLED | GreenLED;
// reset timer A config (not strictly needed)
TACTL = TACLR;
// ACLK as clock source, divider 8, continuous mode, interrupt enabled
TACTL = TASSEL_1 | ID_3 | MC_2 | TAIE;
// set the period
TACCR1 = TIMER_PERIOD;
// enable capture/compare interrupts for CCR1
TACCTL1 = CCIE;
_enable_interrupts();
LPM1;
}
#pragma vector=TIMER0_A1_VECTOR
__interrupt void Timer_A(void)
{
switch (TAIV) {
case TA0IV_TACCR1:
// CCR1 interrupt
RedLEDToggle;
GreenLEDToggle;
// set the time of the next interrupt
TACCR1 += TIMER_PERIOD;
break;
}
}