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460 lines
10 KiB
C++
460 lines
10 KiB
C++
//
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// FILE: ACS712.cpp
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// AUTHOR: Rob Tillaart, Pete Thompson
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// VERSION: 0.3.9
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// DATE: 2020-08-02
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// PURPOSE: ACS712 library - current measurement
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// URL: https://github.com/RobTillaart/ACS712
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#include "ACS712.h"
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// CONSTRUCTOR
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ACS712::ACS712(uint8_t analogPin, float volts, uint16_t maxADC, float mVperAmpere)
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{
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_pin = analogPin;
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_mVperAmpere = mVperAmpere;
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_formFactor = ACS712_FF_SINUS;
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_noisemV = ACS712_DEFAULT_NOISE; // 21mV according to datasheet
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// set in setADC()
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// keep it here until after experimental.
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_maxADC = maxADC;
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_mVperStep = 1000.0 * volts / maxADC; // 1x 1000 for V -> mV
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_mAPerStep = 1000.0 * _mVperStep / _mVperAmpere;
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_midPoint = maxADC / 2;
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// default ADC is internal.
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setADC(NULL, volts, maxADC);
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}
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// MEASUREMENTS
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float ACS712::mA_peak2peak(float frequency, uint16_t cycles)
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{
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uint16_t period = round(1000000UL / frequency);
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if (cycles == 0) cycles = 1;
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float sum = 0;
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for (uint16_t i = 0; i < cycles; i++)
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{
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int minimum, maximum;
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// Better than using midPoint
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minimum = maximum = _analogRead(_pin);
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// find minimum and maximum
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uint32_t start = micros();
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while (micros() - start < period) // UNO ~180 samples...
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{
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int value = _analogRead(_pin);
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if (_suppresNoise) // average 2 samples.
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{
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value = (value + _analogRead(_pin))/2;
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}
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// determine extremes
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if (value < minimum) minimum = value;
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else if (value > maximum) maximum = value;
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}
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sum += (maximum - minimum);
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}
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float peak2peak = sum * _mAPerStep;
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if (cycles > 1) peak2peak /= cycles;
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return peak2peak;
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}
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float ACS712::mA_AC(float frequency, uint16_t cycles)
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{
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uint16_t period = round(1000000UL / frequency);
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if (cycles == 0) cycles = 1;
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float sum = 0;
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// remove float operation from loop.
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uint16_t zeroLevel = round(_noisemV/_mVperStep);
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for (uint16_t i = 0; i < cycles; i++)
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{
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uint16_t samples = 0;
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uint16_t zeros = 0;
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int minimum, maximum;
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minimum = maximum = _analogRead(_pin);
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// find minimum and maximum and count the zero-level "percentage"
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uint32_t start = micros();
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while (micros() - start < period) // UNO ~180 samples...
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{
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samples++;
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int value = _analogRead(_pin);
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if (_suppresNoise) // average 2 samples.
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{
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value = (value + _analogRead(_pin))/2;
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}
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// determine extremes
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if (value < minimum) minimum = value;
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else if (value > maximum) maximum = value;
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// count zeros
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if (abs(value - _midPoint) <= zeroLevel ) zeros++;
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}
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int peak2peak = maximum - minimum;
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// automatic determine _formFactor / crest factor
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float D = 0;
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float FF = 0;
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if (zeros > samples * 0.025) // more than 2% zero's
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{
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D = 1.0 - (1.0 * zeros) / samples; // % SAMPLES NONE ZERO
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FF = sqrt(D) * _formFactor; // ASSUME NON ZERO PART ~ SINUS
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}
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else // # zeros is small => D --> 1 --> sqrt(D) --> 1
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{
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FF = _formFactor;
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}
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// value could be partially pre-calculated: C = 1000.0 * 0.5 * _mVperStep / _mVperAmpere;
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// return 1000.0 * 0.5 * peak2peak * _mVperStep * _formFactor / _mVperAmpere);
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sum += peak2peak * FF;
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}
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float mA = 0.5 * sum * _mAPerStep;
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if (cycles > 1) mA /= cycles;
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return mA;
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}
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float ACS712::mA_AC_sampling(float frequency, uint16_t cycles)
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{
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uint32_t period = round(1000000UL / frequency);
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if (cycles == 0) cycles = 1;
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float sum = 0;
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// float noiseLevel = _noisemV/_mVperStep;
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for (uint16_t i = 0; i < cycles; i++)
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{
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uint16_t samples = 0;
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float sumSquared = 0;
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uint32_t start = micros();
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while (micros() - start < period)
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{
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samples++;
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int value = _analogRead(_pin);
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if (_suppresNoise) // average 2 samples.
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{
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value = (value + _analogRead(_pin))/2;
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}
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float current = value - _midPoint;
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sumSquared += (current * current);
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// not adding noise squared might be more correct for small currents.
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// if (abs(current) > noiseLevel)
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// {
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// sumSquared += (current * current);
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// }
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}
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sum += sqrt(sumSquared / samples);
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}
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float mA = sum * _mAPerStep;
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if (cycles > 1) mA /= cycles;
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return mA;
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}
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float ACS712::mA_DC(uint16_t cycles)
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{
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// read at least twice to stabilize the ADC
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_analogRead(_pin);
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if (cycles == 0) cycles = 1;
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float sum = 0;
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for (uint16_t i = 0; i < cycles; i++)
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{
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int value = _analogRead(_pin);
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if (_suppresNoise) // average 2 samples.
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{
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value = (value + _analogRead(_pin))/2;
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}
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// for RTOS
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if ((i & 0x0001) == 0x0001) // every 2nd iteration
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{
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yield();
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}
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sum += (value - _midPoint);
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}
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float mA = sum * _mAPerStep;
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if (cycles > 1) mA /= cycles;
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return mA;
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}
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// CALIBRATION MIDPOINT
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uint16_t ACS712::setMidPoint(uint16_t midPoint)
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{
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if (midPoint <= _maxADC) _midPoint = (int) midPoint;
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return _midPoint;
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};
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uint16_t ACS712::getMidPoint()
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{
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return _midPoint;
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};
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uint16_t ACS712::incMidPoint()
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{
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if (_midPoint < (int)(_maxADC)) _midPoint += 1;
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return _midPoint;
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};
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uint16_t ACS712::decMidPoint()
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{
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if (_midPoint > 0) _midPoint -= 1;
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return _midPoint;
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};
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// configure by sampling for 2 cycles of AC
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// Also works for DC as long as no current flowing
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// note this is blocking!
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uint16_t ACS712::autoMidPoint(float frequency, uint16_t cycles)
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{
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uint16_t twoPeriods = round(2000000UL / frequency);
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if (cycles == 0) cycles = 1;
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uint32_t total = 0;
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for (uint16_t i = 0; i < cycles; i++)
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{
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uint32_t subTotal = 0;
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uint32_t samples = 0;
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uint32_t start = micros();
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while (micros() - start < twoPeriods)
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{
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uint16_t reading = _analogRead(_pin);
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subTotal += reading;
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samples++;
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// Delaying prevents overflow
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// since we'll perform a maximum of 40,000 reads @ 50 Hz.
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delayMicroseconds(1);
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}
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total += (subTotal / samples);
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}
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_midPoint = (total + (cycles/2))/ cycles; // rounding.
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return _midPoint;
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}
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uint16_t ACS712::autoMidPointDC(uint16_t cycles)
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{
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if (cycles == 0) cycles = 1;
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uint32_t total = 0;
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for (uint16_t i = 0; i < cycles; i++)
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{
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total += analogRead(_pin);
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}
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_midPoint = (total + (cycles/2))/ cycles; // rounding.
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return _midPoint;
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}
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uint16_t ACS712::resetMidPoint()
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{
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_midPoint = _maxADC / 2;
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return _midPoint;
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};
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// CALIBRATION FORM FACTOR
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void ACS712::setFormFactor(float formFactor)
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{
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_formFactor = formFactor;
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};
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float ACS712::getFormFactor()
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{
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return _formFactor;
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};
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// CALIBRATION NOISE
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// noise defaults 21 datasheet
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void ACS712::setNoisemV(uint8_t noisemV)
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{
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_noisemV = noisemV;
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};
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uint8_t ACS712::getNoisemV()
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{
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return _noisemV;
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};
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float ACS712::mVNoiseLevel(float frequency, uint16_t cycles)
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{
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float mA = mA_peak2peak(frequency, cycles);
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// divide by 2 as the level is half of the peak to peak range
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return mA * _mVperAmpere * 0.001 / 2;
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}
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void ACS712::suppressNoise(bool flag)
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{
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_suppresNoise = flag;
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}
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// CALIBRATION mV PER AMP
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// Adjusting resolution AC and DC
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void ACS712::setmVperAmp(float mVperAmpere)
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{
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_mVperAmpere = mVperAmpere;
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_mAPerStep = 1000.0 * _mVperStep / _mVperAmpere;
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};
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float ACS712::getmVperAmp()
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{
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return _mVperAmpere;
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};
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float ACS712::getmAPerStep()
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{
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return _mAPerStep;
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};
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float ACS712::getAmperePerStep()
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{
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return _mAPerStep * 0.001;
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};
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// FREQUENCY DETECTION
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// uses oversampling and averaging to minimize variation
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// blocks for substantial amount of time, depending on minimalFrequency
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float ACS712::detectFrequency(float minimalFrequency)
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{
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int maximum = 0;
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int minimum = 0;
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maximum = minimum = _analogRead(_pin);
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// determine maxima
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uint32_t timeOut = round(1000000.0 / minimalFrequency);
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uint32_t start = micros();
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while (micros() - start < timeOut)
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{
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int value = _analogRead(_pin);
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if (value > maximum) maximum = value;
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if (value < minimum) minimum = value;
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}
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// calculate quarter points
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// using quarter points is less noise prone than using one single midpoint
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int Q1 = (3 * minimum + maximum ) / 4;
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int Q3 = (minimum + 3 * maximum ) / 4;
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// 10x passing Quantile points
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// wait for the right moment to start
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// to prevent endless loop a timeout is checked.
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timeOut *= 10;
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start = micros();
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// casting to int to keep compiler happy.
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while ((int(_analogRead(_pin)) > Q1) && ((micros() - start) < timeOut));
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while ((int(_analogRead(_pin)) <= Q3) && ((micros() - start) < timeOut));
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start = micros();
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for (int i = 0; i < 10; i++)
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{
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while ((int(_analogRead(_pin)) > Q1) && ((micros() - start) < timeOut));
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while ((int(_analogRead(_pin)) <= Q3) && ((micros() - start) < timeOut));
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}
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uint32_t stop = micros();
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// calculate frequency
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float wavelength = stop - start;
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float frequency = 1e7 / wavelength;
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if (_microsAdjust != 1.0) frequency *= _microsAdjust;
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return frequency;
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}
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// timing for FREQUENCY DETECTION
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void ACS712::setMicrosAdjust(float factor)
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{
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_microsAdjust = factor;
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};
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float ACS712::getMicrosAdjust()
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{
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return _microsAdjust;
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};
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// DEBUG
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uint16_t ACS712::getMinimum(uint16_t milliSeconds)
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{
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uint16_t minimum = _analogRead(_pin);
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// find minimum
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uint32_t start = millis();
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while (millis() - start < milliSeconds)
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{
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uint16_t value = _analogRead(_pin);
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if (value < minimum) minimum = value;
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}
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return minimum;
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}
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uint16_t ACS712::getMaximum(uint16_t milliSeconds)
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{
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uint16_t maximum = _analogRead(_pin);
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// find maximum
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uint32_t start = millis();
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while (millis() - start < milliSeconds)
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{
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uint16_t value = _analogRead(_pin);
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if (value > maximum) maximum = value;
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}
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return maximum;
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}
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void ACS712::setADC(uint16_t (* f)(uint8_t), float volts, uint16_t maxADC)
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{
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_readADC = f;
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_maxADC = maxADC;
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_mVperStep = 1000.0 * volts / maxADC; // 1x 1000 for V -> mV
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_mAPerStep = 1000.0 * _mVperStep / _mVperAmpere;
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_midPoint = maxADC / 2;
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}
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//////////////////////////////////////////////////////////////////////
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//
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// PRIVATE
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//
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uint16_t ACS712::_analogRead(uint8_t pin)
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{
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// if external ADC is defined use it.
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if (_readADC != NULL) return _readADC(pin);
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return analogRead(pin);
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}
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// -- END OF FILE --
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