Timer capture mode not triggering ISR

RyanN said:

TACCTL0 = CCIS0 + SCS + CAP + CCIE + CM_1;

You set CCIS0, which is the LSB of the CCIS bitfield and selects (if CCIS1 is clear) CCI0B.
You probably wanted to set CCIS_0, which is the first option of this bitfieald and equals 0x00 (none of the two bits set).

I have adjusted my code some and appear to have interrupts firing now but there is still 

something wrong that I cannot figure out. 

I created a overflow counter that should count the amount of times that the counter 

recycles back to 0.

I think it is working correctly because I enter the ISR for TIMER0_A0_VECTOR. however 

it doesnt appear that my counter is incrementing.

It also seems like the other ISR is firing off too fast. previously I had an array that I would 

save the counter differences to, 10 times.

Whenever the program got 10 data points a breakpoint would pause the program and I 

would observe the values. 

I am feeding in a signal of 2Hz and the program would pause after only running no more 

than a second. This is clearly wrong. 

I am unsure if the interrupt is being called for the rising edge or if there is some other cause. 

Is there a built in interrupt that will fire whenever the counter rolls over or should I 

continue doing what I am doing?

Any suggestions or comments would be appreciated. I have been working on this 

problem for a while and still no luck. 

Thanks 

#include "msp430g2353.h"

unsigned int count1, count2, ovCnt;
int diff;
	
void main(void){
 WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

 BCSCTL1 = CALBC1_1MHZ; // Set DCO to 1MHz
 DCOCTL = CALDCO_1MHZ;
	
 P1DIR = BIT6; // Set P1.0 out,1.1 input dir
 P1OUT &= BIT6; // LED on
	
 P1DIR &= ~BIT2; //Port 1.2/TACCR1 - Input
 P1SEL |= BIT2; // Select Timer Capture option
    
 TACTL = TASSEL_2 + TACLR + MC_2; // SMCLK = 1 Mhz, continuous mode
 TACCTL1 = CM_1+CCIS_0+SCS+CAP+CCIE; // CCR1 used for timer capture
   // capture on rising edge, CCI0
  // Enable timer interrupt
 TACCR0 = 0xFFFF;   //Set mode to watch for timer max
 TACCTL0 = CM_0 + CCIS_0 + CCIE;  //CCR0 enabled interrupt, compare mode 
                                        
 TACTL |= MC_2; // Start Timer, Continuous mode

 count1 = 0; count2 = 0; //initialize variables
 index = 0; ovCnt = 0;
	                                            
 _BIS_SR(LPM0_bits + GIE); // Enter LPM0 w/ interrupt
	
 while(1){};
}

/*
* used to count the amount of times the counter rolls over
*/
#pragma vector=TIMER0_A0_VECTOR
__interrupt void overflow_counter(void){
 ovCnt++; //increment overflow counter
}

/*
* used to get count of times of signal rising edge
*/
#pragma vector=TIMER0_A1_VECTOR
__interrupt void TimerCapture(void){
 _DINT();
 switch(TAIV){
 case TA0IV_TACCR1://0x02:
 TACCTL1 ^= CCIFG; //clear interrupt flag
			
 P1OUT ^= BIT6; // Toggle P1.0 using exclusive-OR
			
 if(count1 == 0 && count2 == 0){ //get time of first edge
 count1 = TACCR1;
 ovCnt = 0;
 }else if(count1 != 0 && count2 == 0){ //get time of second edge
 count2 = TACCR1;
 if(count1 > count2){ //count1 has a higher count
 diff = ((0xFFFF - count1) + count2) + ((ovCnt - 1) * 0xFFFF);
 }else if(count1 < count2){ //count2 has a higher count
 diff = (count2 - count1) + ((ovCnt) * 0xFFFF);
 }
 count1 = 0;
 count2 = 0; //<<----breakpoint here
 }
 break;
 case TA0IV_TAIFG://0x0A://COV:
// ovCnt++;
// TACCTL1 ^= COV; 
 break;
 }
 _EINT();
}

Thank you very much for your assistance. I believe that I have mostly figured it out but once

again something doesnt seem to be working correctly. 

I changed my calculation function to the following: (I believe this should work for any values received)

diff = (((0xFFFF - count1) + count2) + ((ovCnt - 1) * 0xFFFF));

and when I do the math by hand using the gathered values I get the right value I would expect for

a given input frequency.

However the microcontroller always gets the wrong value. I noticed this earlier today on another section 

of my code as well (when trying to convert a Celsius temp to a Fahreneit temp). Is there a limitation with

the MSP430 when it comes to calculations such as this?

I changed my calculations to the following just to see if I could find out what was up,

but I am unable to see the value of temp1, and temp2. 

unsigned int temp, temp1, temp2;
temp = ((0xFFFF - count1) + count2);
temp1 = (ovCnt - 1);
temp2 = (temp1 * 0xFFFF);
diff = temp + temp2;

I assume this is caused by the debugger but was wondering if there was a way to 

fix this so that I could see the values. 

I figured out that my problem was that I was using an integer to store the difference even

though the value was more than what a 16-bit integer could store. 

Now I am using doubles and everything seems to be working fine. 

I am still curious as to why some values are able to be

seen in the debugger and why some cant be seen.

RyanN said:

I figured out that my problem was that I was using an integer to store the difference even though the value was more than what a 16-bit integer could store.

x*0xffff will result in 0x10000-x, since 0xffff and x are both integers, so the result is truncated to an integer.

Using (long)0xFFFF, or, as it is faster, using "(long)(x)<<16", which is actually x*(long)0x10000, but much, much faster than a multiplication) would have resulted in the multiplication being done in long range (32 bit). However, the difference building before would still be subject to truncation since (here again (long)0xFFFF is required, so a long value of 65535L is used to do the additions and subtraction.
However, if the variable DIV wher ethe result is stored to, is only a 16 bit int, then you have the correctly calculated result still truncated.

RyanN said:

Now I am using doubles and everything seems to be working fine. 

Make the variables unsigned long (so they store 32bit up to 0xFFFFFFFF) is by magnitudes faster and more than just a bit smaller.

RyanN said:

I am still curious as to why some values are able to be seen in the debugger and why some cant be seen.

In case of local variables, they may solely exist in a processor register. In this case, mabye no reference is generated for it at all and the debugger doesn't know of its existence. It depends on how much the compiler can tell the debugger about the variables.
The variable, while being declare at funciton start, may even ot exist at all until required. Or may have been optimized away totally, since it was of no use (e.g. it had a fixed value, so in the generated binary, an immediate value was used rather than a variable). Also, if the variable is not used anymore later in the code, it may be discarded and the register is used for something else later.

The first goal of a (microcontroller) compiler is to produce fast and efficient code, not to support debugging at the expense of unnecessarily big and slow code.

Personally, I never used a debugger for the MSP. Never.

Some How you have executed your ISR successfully for capture mode.

But, I can not get in to the capture ISR by writing below code.

#include <msp430.h>

int main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT

__enable_interrupt();
P1DIR |= 0x01; //  P1.0 as o/p direction
P1DIR &= ~0x02;  // P1.1 as inpur direction
P1SEL &= ~0x01; // P1.0 for I/O operation
P1SEL |= 0x02; // P1.1 for capture input 
P1OUT &= ~0x01; // LED P1.0 output zero

CCTL0 = CAP + SCS + CM_1 + CCIE + CCIS_0; // CCR0 interrupt enabled

TACTL = TASSEL_1 + MC_2; 

__bis_SR_register(LPM3_bits + GIE); // Enter LPM3 w/ interrupt

while(1);
}

#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A (void)

{

P1OUT ^= 0x01 ; // Toggle P1.0 using exclusive-OR

}

I can not be able to toggle LED, means even i am giving rising edges to P1.1 port.

Please help. 

It would be really helpful to know on which MSP you’re working. Because port pin functions are device specific.

I am working on : MSP430F1122 Controller.

Launch Pad : MSP-TS430PW28 Texas Instrumentation Launch Pad.

I am giving giving falling edges within interval of 6 milli seconds, so if any delay by SCS bit it will be tolerable.

Regarding giving edges, i have verified that by giving similar edges 

i have successfully detect positive to negative edges by giving it to pin

configured as general purpose input (GPIO PIN). So I think edges i am giving are proper.

But there is some thing wrong when I am going for capture edges.

Please help.

I guess I found what’s happening.
In your case, ‘any’ delay will be ‘eternal’ delay. You’re running the timer from ACLK (TASSEL_1). However, on 1x family, ACLK needs an external crystal on XT1 to have any frequency at all.
No timer clock, no synchronize (SCS bit), no capture, no interrupt. Your code doesn’t select any load capacitors for an external watch crystal nor does it set XT1 for HF crystal or bypass operation.
Try using TASSEL_2 to use SMCLK (which runs from DCO, with about 600kHz by default) as timer clock. Or connect a crystal to XT1 to give ACLK a source.