TSL235R inconsistent output

system · May 6, 2014, 8:18pm

I've updated my code to the following as per the suggestions:

unsigned long period = 100000;
float area = 0.0092; // Sensing area of TSL25R device, in cm2

volatile unsigned long pulses = 0;
unsigned long lastPulseCount = 0;
unsigned long lastPulseOutputTime = 0;

void irq1()
{
  pulses++;
}

///////////////////////////////////////////////////////////////////
//
// SETUP
//
void setup() 
{
  Serial.begin(115200);
  Serial.println("START");
  pinMode(2, INPUT);
  digitalWrite(2, HIGH);
  attachInterrupt(0, irq1, RISING);
}

///////////////////////////////////////////////////////////////////
//
// MAIN LOOP
//
void loop() 
{
  unsigned long elapsedTimeSincePulseCheck = micros() - lastPulseOutputTime;

  if (elapsedTimeSincePulseCheck >= period)
  {
    lastPulseOutputTime = micros();
    
    noInterrupts();
    unsigned long pulsesCopy = pulses;
    interrupts();
    unsigned long pulsesSince = pulsesCopy- lastPulseCount;
    
    unsigned long frequency = getFrequency(elapsedTimeSincePulseCheck, pulsesSince); 
    long radiance = getRadiance(frequency);
    
    Serial.println(frequency);
  
    lastPulseCount = pulsesCopy;
  }
}

unsigned long getFrequency(unsigned long timePeriod, unsigned long pulseCount) {
  unsigned long hz = (pulseCount) * (1000000 / timePeriod);
  return hz;
}

long getRadiance(unsigned long frequency) {
  long irradiance = frequency / area;  // Calculate Irradiance (uW/cm2)
  return (irradiance);
}

However the output is still showing the same issues if oddly worse now, the graph of frequency looks as follows:

With the raw data being:

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TSL235R inconsistent output

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