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Jira-507 and 514: 1. Bug corrected in timer ISR where the clearing of… #117

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Jira-507 and 514: 1. Bug corrected in timer ISR where the clearing of… #117

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26 changes: 18 additions & 8 deletions libraries/CurieTimerOne/CurieTimer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -153,7 +153,8 @@ int CurieTimer::pwmStart(unsigned int outputPin, double dutyPercentage, unsigned
{
unsigned int pwmPeriod;

if(periodUsec == 0)
// Safe guard against periodUsec overflow when convert to hz.
if((periodUsec == 0) || (periodUsec >= MAX_PERIOD))
return -(INVALID_PERIOD);

if((dutyPercentage < 0.0) || (dutyPercentage > 100.0))
Expand All @@ -179,11 +180,20 @@ int CurieTimer::pwmStart(unsigned int outputPin, double dutyPercentage, unsigned
dutyCycle = (unsigned int)(((double)pwmPeriod / 100.0) * dutyPercentage);
nonDutyCycle = pwmPeriod - dutyCycle;

// S/w overhead is about 4-5 usec. The shortest up or down cycle is set to be 10 usec.
if(dutyCycle < (10 * HZ_USEC))
dutyCycle = (10 * HZ_USEC);
if(nonDutyCycle < (10 * HZ_USEC))
nonDutyCycle = (10 * HZ_USEC);

// Account for s/w overhead.
dutyCycle -= (4 * HZ_USEC);
nonDutyCycle -= (4 * HZ_USEC);

dutyToggle = true;
digitalWrite(pwmPin, HIGH);
init(dutyCycle, pwmCB);

return SUCCESS;
// Should return value back to caller.
return init(dutyCycle, pwmCB);
}


Expand Down Expand Up @@ -255,14 +265,14 @@ inline void CurieTimer::timerIsr(void)
{
unsigned int reg;

// Clear the interrupt pending bit.
reg = aux_reg_read(timerControlAddr) & ~ARC_TIMER_INTR_PENDING_BIT_FLAG;
aux_reg_write(timerControlAddr, reg);

tickCnt++; // Account for the interrupt

if(userCB != NULL) // Call user ISR if available
userCB();

// Clear the interrupt pending bit upon exit.
reg = aux_reg_read(timerControlAddr) & ~ARC_TIMER_INTR_PENDING_BIT_FLAG;
aux_reg_write(timerControlAddr, reg);
}


4 changes: 2 additions & 2 deletions libraries/CurieTimerOne/CurieTimer.h
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Expand Up @@ -124,8 +124,8 @@ class CurieTimer
// Start software PWM. Use a range of 0-1023 for duty cycle. 0=always Low, 1023=always high
int pwmStart(unsigned int outputPin, int dutyRange, unsigned int periodUsec);

// Stop software PWM.
inline void pwmStop(void) { return kill(); }
// Stop software PWM. Put the time back to default and de-assert the selected port.
inline void pwmStop(void) { kill(); return digitalWrite(pwmPin, LOW); }

// Generic timer ISR. It will call user call back routine if set.
void timerIsr(void);
Expand Down