const unsigned long sampleTime = 100000UL;  // sample over 100ms, it is an exact number of cycles for both 50Hz and 60Hz mains
const unsigned long numSamples = 250UL;     // choose the number of samples to divide sampleTime exactly, but low enough for the ADC to keep up
const unsigned long sampleInterval = sampleTime/numSamples;  // the sampling interval, must be longer than then ADC conversion time
const int adc_zero = 511;

float current = 0.0f;
const int currentPin = 0;


void setup() {
}

void loop() {
 unsigned long currentAcc = 0;
 unsigned int count = 0;
 unsigned long prevMicros = micros () - sampleInterval;

 while (count < numSamples) {
   if (micros () - prevMicros >= sampleInterval) {
     int adc_raw = analogRead (currentPin) - adc_zero;
     currentAcc += (unsigned long) (adc_raw * adc_raw);
     ++ count;
     prevMicros += sampleInterval;
   }
 }

 float rms = sqrt((float)currentAcc/(float)numSamples) * (75.7576 / 1024.0);

 current += 0.2f * (rms - current);