Timer CCP ISR

KM01

Hello,I am trying to build an input capture function into my controller. I have enabled the pin/timer as specified as below. Every edge, I jump into the timer ISR and increase the edge count. After one second, of monitoring a squarewave I read the edge count. It appears the edge count is always double what it should be. I have confirmed I am only triggering an ISR jump on the one edge specified. Does anyone else have suggestions of why my edge count would be double what I expect?

ENABLE PIN/TIMER: 
IC_Properties[DIN01].ICstatus = TRUE; 
IC_Properties[DIN01].ICEdgeCount = 0; 
IC_Properties[DIN01].TimerInterrupt = INT_TIMER5A; 
ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER5); 
ROM_GPIOPinTypeTimer(GPIO_PORTM_BASE, GPIO_PIN_2); 
ROM_GPIOPinConfigure(GPIO_PM2_T5CCP0); 
ROM_IntMasterEnable(); 
ROM_TimerLoadSet(TIMER5_BASE, TIMER_A, 1); 
ROM_TimerMatchSet(TIMER5_BASE, TIMER_A, 0); 
ROM_TimerControlEvent(TIMER5_BASE, TIMER_A, TIMER_EVENT_NEG_EDGE); 

if (IC_Properties[DIN02].ICstatus == FALSE) { 
    ROM_TimerConfigure(TIMER5_BASE, (TIMER_CFG_SPLIT_PAIR | TIMER_CFG_A_CAP_COUNT)); 
    IC_Properties[DIN01].TimerConfig = TIMER_A; 
} 
else { 
    ROM_TimerConfigure(TIMER5_BASE, (TIMER_CFG_SPLIT_PAIR | TIMER_CFG_B_CAP_COUNT | TIMER_CFG_A_CAP_COUNT)); 
    IC_Properties[DIN01].TimerConfig = TIMER_BOTH; 
} 

ROM_IntEnable(INT_TIMER5A); 
ROM_TimerIntEnable(TIMER5_BASE, IC_Properties[DIN01].TimerConfig); 
ROM_TimerEnable(TIMER5_BASE, TIMER_A); 



void Timer_5_subtimer_A_ISR(void) { 
    ROM_IntDisable(IC_Properties[DIN01].TimerInterrupt); 
    ROM_TimerIntClear(TIMER5_BASE, IC_Properties[DIN01].TimerConfig); 
    IC_Properties[DIN01].ICEdgeCount += 1; 
    ROM_TimerEnable(TIMER5_BASE, IC_Properties[DIN01].TimerConfig); 
    ROM_IntEnable(IC_Properties[DIN01].TimerInterrupt); 
}

firmed I am only triggering an ISR jump on the one edge specified. Does anyone else have suggestions of why my edge count would be double what I expect?

over 9 years ago

0 Amit Ashara over 9 years ago

TI__Guru**** 244400 points

Hello KM01,

You are disabling the interrupt in the interrupt handler and then clearing the interrupt source. You do not need to do the same. Simply clear the interrupt increment the count and then exit.

Regards
Amit

0 KM01 over 9 years ago in reply to Amit Ashara

Intellectual 295 points

So I reduced my ISR down to the snippet seen below. I still experience the same results. Per your instructions, I believe you also wanted me to remove the TimerEnable command; however, commenting this out of the code prevents the timer from matching and interrupting. Have I done what you expected?

void Timer_5_subtimer_A_ISR(void) {
ROM_TimerIntClear(TIMER5_BASE, TIMER_CAPA_MATCH);
IC_Properties[DIN01].ICEdgeCount += 1;
ROM_TimerEnable(TIMER5_BASE, IC_Properties[DIN01].TimerConfig);
}

0 Amit Ashara over 9 years ago in reply to KM01

TI__Guru**** 244400 points

Hello KM01,

Can you perform a simple experiment: Put a breakpoint on the TimerEnable function in the interrupt handler. Now provide a single falling edge. Once the break-point gets triggered, step through the ISR to see if it gets triggered again. Also make a note of the registers before and after the step operation.

Regards
Amit

0 KM01 over 9 years ago in reply to Amit Ashara

Intellectual 295 points

Amit,

I place a breakpoint on the TimerEnable function. I provided a single falling edge and stepped through from the breakpoint. The ISR does not get triggered again. The only register change is the timer enable bit getting set.

0 Amit Ashara over 9 years ago in reply to KM01

TI__Guru**** 244400 points

Hello KM01,

OK. So now add a small delay look like SysCtlDelay(5) after the enable function and now run the code. Does it double increment?

Regards
Amit

0 KM01 over 9 years ago in reply to Amit Ashara

Intellectual 295 points

Amit,

It still double increments.

0 Amit Ashara over 9 years ago in reply to KM01

TI__Guru**** 244400 points

Hello KM01,

Can you please send in a simplified code base for CCS so that I can see what is going on?

Regards
Amit

0 KM01 over 9 years ago in reply to Amit Ashara

Intellectual 295 points

Amit,

I have found the source of the issue. It turned out to be a test setup problem. Thank you for your time and for helping increase the efficiency of my ISR with your earlier suggestions.

Thanks.

0 Amit Ashara over 9 years ago in reply to KM01

TI__Guru**** 244400 points

Hello KM01,

I believe that should have been my first question...

Regards
Amit

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Timer CCP ISR