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0.3.5 ACS712
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rob tillaart
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@ -1,7 +1,7 @@
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//
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// FILE: ACS712.cpp
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// AUTHOR: Rob Tillaart, Pete Thompson
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// VERSION: 0.3.4
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// VERSION: 0.3.5
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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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@ -26,7 +26,7 @@ ACS712::ACS712(uint8_t analogPin, float volts, uint16_t maxADC, float mVperAmper
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_midPoint = maxADC / 2;
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// default ADC is internal.
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setADC(_internalAnalog, volts, maxADC);
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setADC(NULL, volts, maxADC);
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}
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@ -42,16 +42,16 @@ float ACS712::mA_peak2peak(float frequency, uint16_t cycles)
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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 = _readADC(_pin);
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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 = _readADC(_pin);
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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 + _readADC(_pin))/2;
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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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@ -82,17 +82,17 @@ float ACS712::mA_AC(float frequency, uint16_t cycles)
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uint16_t zeros = 0;
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int _min, _max;
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_min = _max = _readADC(_pin);
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_min = _max = _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 = _readADC(_pin);
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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 + _readADC(_pin))/2;
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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 < _min) _min = value;
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@ -144,10 +144,10 @@ float ACS712::mA_AC_sampling(float frequency, uint16_t cycles)
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while (micros() - start < period)
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{
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samples++;
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int value = _readADC(_pin);
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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 + _readADC(_pin))/2;
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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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@ -169,15 +169,15 @@ float ACS712::mA_AC_sampling(float frequency, uint16_t cycles)
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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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_readADC(_pin);
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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 = _readADC(_pin);
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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 + _readADC(_pin))/2;
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value = (value + _analogRead(_pin))/2;
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}
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sum += (value - _midPoint);
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}
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@ -233,7 +233,7 @@ uint16_t ACS712::autoMidPoint(float frequency, uint16_t cycles)
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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 = _readADC(_pin);
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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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@ -329,14 +329,14 @@ 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 = _readADC(_pin);
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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 = _readADC(_pin);
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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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@ -352,13 +352,13 @@ float ACS712::detectFrequency(float minimalFrequency)
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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(_readADC(_pin)) > Q1) && ((micros() - start) < timeOut));
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while ((int(_readADC(_pin)) <= Q3) && ((micros() - start) < timeOut));
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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(_readADC(_pin)) > Q1) && ((micros() - start) < timeOut));
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while ((int(_readADC(_pin)) <= Q3) && ((micros() - start) < timeOut));
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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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@ -386,13 +386,13 @@ float ACS712::getMicrosAdjust()
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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 = _readADC(_pin);
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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 = _readADC(_pin);
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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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@ -401,13 +401,13 @@ uint16_t ACS712::getMinimum(uint16_t milliSeconds)
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uint16_t ACS712::getMaximum(uint16_t milliSeconds)
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{
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uint16_t maximum = _readADC(_pin);
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uint16_t maximum = _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 = _readADC(_pin);
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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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@ -425,5 +425,17 @@ void ACS712::setADC(uint16_t (* f)(uint8_t), float volts, uint16_t maxADC)
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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 extern 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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@ -2,7 +2,7 @@
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//
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// FILE: ACS712.h
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// AUTHOR: Rob Tillaart, Pete Thompson
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// VERSION: 0.3.4
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// VERSION: 0.3.5
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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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@ -13,7 +13,7 @@
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#include "Arduino.h"
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#define ACS712_LIB_VERSION (F("0.3.4"))
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#define ACS712_LIB_VERSION (F("0.3.5"))
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// ACS712_FF_SINUS == 1.0/sqrt(2) == 0.5 * sqrt(2)
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@ -123,16 +123,10 @@ class ACS712
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// EXPERIMENTAL 0.3.4
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// supports up to 16 bits ADC.
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uint16_t (* _readADC)(uint8_t);
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uint16_t _analogRead(uint8_t pin);
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};
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// wrapper for internal analogRead()
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// solves platform specific casting.
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static uint16_t _internalAnalog(uint8_t pin)
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{
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return analogRead(pin);
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}
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// -- END OF FILE --
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@ -6,13 +6,19 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
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and this project adheres to [Semantic Versioning](http://semver.org/).
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## [0.3.5] - 2023-01-18
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- fix #33 failing build => issue 345 created @ arduino-ci
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- redo **setADC()**
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- allows reset to internal **analogRead()** too now.
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- update README.md
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## [0.3.4] - 2023-01-14
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- experimental
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- add **void setADC()** to use an external ADC for measurements.
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- add **static uint16_t internalAnalog(uint8_t p)** wrapping analogRead() - solves casting.
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- add example ACS712_20_DC_external_ADC.ino
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## [0.3.3] - 2023-01-03
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- update GitHub actions
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- update license
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@ -21,7 +21,7 @@
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"type": "git",
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"url": "https://github.com/RobTillaart/ACS712.git"
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},
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"version": "0.3.4",
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"version": "0.3.5",
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"license": "MIT",
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"frameworks": "arduino",
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"platforms": "*",
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@ -1,5 +1,5 @@
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name=ACS712
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version=0.3.4
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version=0.3.5
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author=Rob Tillaart <rob.tillaart@gmail.com>, Pete Thompson <pete.thompson@yahoo.com>
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maintainer=Rob Tillaart <rob.tillaart@gmail.com>
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sentence=ACS712 library for Arduino.
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@ -275,21 +275,55 @@ Current version is experimental and not performance optimized.
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#### setADC (experimental 0.3.4)
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- **void setADC(uint16_t (\*)(uint8_t), float volts, uint16_t maxADC)** sets the ADC function and its parameters.
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Defaults the internal **analogRead()** by this wrapper in ACS712.h:
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- **void setADC(uint16_t (\*)(uint8_t), float volts, uint16_t maxADC)** sets the ADC function and the parameters of the used ADC.
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The library uses the internal **analogRead()** as default.
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Be sure to set the parameters of the ADC correctly.
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The easiest way to implement an external ADC is to make a wrapper function as casting for
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function pointer is a no go area.
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```cpp
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static uint16_t _internalAnalog(uint8_t pin)
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// set to external ADC - 5 volts 12 bits
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ACS.setADC(myAnalogRead, 5.0, 4096);
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...
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uint16_t myAnalogRead(uint8_t pin)
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{
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return analogRead(pin);
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return MCP.read(pin); // assuming MCP is ADC object.
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}
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```
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Be sure to set the parameters of the constructor correctly.
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To reset to the internal ADC use **NULL** as function pointer.
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Be sure to set the parameters of the ADC correctly.
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```cpp
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// reset to internal ADC - 5 volts 10 bits
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ACS.setADC(NULL, 5.0, 1023);
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```
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- example ACS712_20_DC_external_ADC.ino
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- https://github.com/RobTillaart/ACS712/issues/31
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Note that the use of an external ADC should meet certain performance requirements,
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especially for measuring **ma-AC()**.
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To 'catch' the peaks well enough one needs at least 2 samples per millisecond
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for a 60 Hz signal.
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The 16 bit I2C **ADS1115** in continuous mode gives max 0.8 samples per millisecond.
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This will work perfect for high resolution **mA-DC()** but is not fast enough for
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doing **mA-AC()**.
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The SPI based **MCP3202** ao can do up to 100 samples per millisecond at 12 bit.
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These ADC's are perfect both **mA-DC()** and **mA-AC()**.
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- https://github.com/RobTillaart/ADS1X15
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- https://github.com/RobTillaart/MCP_ADC
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## Voltage divider
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As per issue #15 in which an ACS712 was connected via a voltage divider to the ADC of an ESP32.
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@ -332,7 +366,8 @@ To detect that the ACS712 is disconnected from the ADC one could connect the
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analog pin via a pull-down to GND. A pull-up to VCC is also possible.
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Choose the solution that fits your project best. (Think safety).
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**mA_DC()** and **mA_AC_sampling()** will report HIGH values (Out of range) when the ACS712 is disconnected.
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**mA_DC()** and **mA_AC_sampling()** will report HIGH values (Out of range) when
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the ACS712 is disconnected.
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The other - peak2peak based functions - will see this as zero current (min == max).
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Schema with PULL-UP.
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@ -362,32 +397,23 @@ The examples show the basic working of the functions.
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#### Should - 0.3.x
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- investigate noise suppression #21 (0.3.1 and later)
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#### Could
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- merge **mA_AC()** and **mA_AC_sampling()** into one. (0.4.0)
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- or remove - depreciate - the worst one
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- investigate blocking calls:
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- **mA_AC()** blocks for about 20 ms at 50 Hz.
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This might affect task scheduling on a ESP32. Needs to be investigated.
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Probably need a separate thread that wakes up when new analogRead is available?
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- RTOS specific class?
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- **detectFrequency(float)** blocks pretty long.
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- other set functions also a range check?
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- split the readme.md in multiple documents?
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- which?
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#### Won't
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#### Could
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- merge **mA_AC()** and **mA_AC_sampling()** into one. (0.4.0)
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- or remove - depreciate - the worst one
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- add range check to (all) set functions?
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#### Won't (unless requested)
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- external analogue read support? separate class!
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- after this one stabilized.
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- ACS712X class with external ADC ( 16 or even 24 bit)
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- keep interface alike?
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- are these fast enough for e.g. 60 Hz (100 samples in 16 millis?)
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- **ADS1115** in continuous mode ==> 0.8 samples per millisecond at 16 bit Ideal for **mA-DC()**
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- **MCP3202** SPI interface ==> up to 100 samples per millisecond !! at 12 bit. Perfect.
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- investigate support for micro-Amperes. **ACS.uA_DC()**
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- need a very stable voltage
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- needs a 24 bit ADC
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@ -400,4 +426,8 @@ The examples show the basic working of the functions.
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- midPoint can be a float so it can be set more exact.
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- extra precision is max half bit = smaller than noise?
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- math will be slower during sampling (UNO)
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- split the readme.md in multiple documents?
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- which?
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- setADC() to support > 16 bit?
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- uint32_t performance penalty?
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