add setADC() (#32)

* add setADC() for external ADC

ACS712.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: ACS712.cpp
 //  AUTHOR: Rob Tillaart, Pete Thompson
-// VERSION: 0.3.3
+// VERSION: 0.3.4
 //    DATE: 2020-08-02
 // PURPOSE: ACS712 library - current measurement
 //     URL: https://github.com/RobTillaart/ACS712
@@ -14,13 +14,19 @@
 ACS712::ACS712(uint8_t analogPin, float volts, uint16_t maxADC, float mVperAmpere)
 {
   _pin         = analogPin;
+  _mVperAmpere = mVperAmpere;
+  _formFactor  = ACS712_FF_SINUS;
+  _noisemV     = ACS712_DEFAULT_NOISE;    //  21mV according to datasheet
+
+  //  set in setADC() 
+  //  keep it here until after experimental.
   _maxADC      = maxADC;
   _mVperStep   = 1000.0 * volts / maxADC;  //  1x 1000 for V -> mV
-  _mVperAmpere = mVperAmpere;
   _mAPerStep   = 1000.0 * _mVperStep / _mVperAmpere;
-  _formFactor  = ACS712_FF_SINUS;
   _midPoint    = maxADC / 2;
-  _noisemV     = ACS712_DEFAULT_NOISE;    //  21mV according to datasheet
+
+  //  default ADC is internal.
+  setADC(_internalAnalog, volts, maxADC);
 }
 
 
@@ -36,16 +42,16 @@ float ACS712::mA_peak2peak(float frequency, uint16_t cycles)
   {
     int minimum, maximum;
     //  Better than using midPoint
-    minimum = maximum = analogRead(_pin);
+    minimum = maximum = _readADC(_pin);
 
     //  find minimum and maximum
     uint32_t start = micros();
-    while (micros() - start < period)  // UNO ~180 samples...
+    while (micros() - start < period)  //  UNO ~180 samples...
     {
-      int value = analogRead(_pin);
+      int value = _readADC(_pin);
       if (_suppresNoise)               //  average 2 samples.
       {
-        value = (value + analogRead(_pin))/2;
+        value = (value + _readADC(_pin))/2;
       }
       //  determine extremes
       if (value < minimum) minimum = value;
@@ -76,17 +82,17 @@ float ACS712::mA_AC(float frequency, uint16_t cycles)
     uint16_t zeros   = 0;
 
     int _min, _max;
-    _min = _max = analogRead(_pin);
+    _min = _max = _readADC(_pin);
 
     //  find minimum and maximum and count the zero-level "percentage"
     uint32_t start = micros();
     while (micros() - start < period)  // UNO ~180 samples...
     {
       samples++;
-      int value = analogRead(_pin);
+      int value = _readADC(_pin);
       if (_suppresNoise)  //  average 2 samples.
       {
-        value = (value + analogRead(_pin))/2;
+        value = (value + _readADC(_pin))/2;
       }
       //  determine extremes
       if (value < _min) _min = value;
@@ -138,10 +144,10 @@ float ACS712::mA_AC_sampling(float frequency, uint16_t cycles)
     while (micros() - start < period)
     {
       samples++;
-      int value = analogRead(_pin);
+      int value = _readADC(_pin);
       if (_suppresNoise)  //  average 2 samples.
       {
-        value = (value + analogRead(_pin))/2;
+        value = (value + _readADC(_pin))/2;
       }
       float current = value - _midPoint;
       sumSquared += (current * current);
@@ -163,15 +169,15 @@ float ACS712::mA_AC_sampling(float frequency, uint16_t cycles)
 float ACS712::mA_DC(uint16_t cycles)
 {
   //  read at least twice to stabilize the ADC
-  analogRead(_pin);
+  _readADC(_pin);
   if (cycles == 0) cycles = 1;
   float sum = 0;
   for (uint16_t i = 0; i < cycles; i++)
   {
-    int value = analogRead(_pin);
+    int value = _readADC(_pin);
     if (_suppresNoise)  //  average 2 samples.
     {
-      value = (value + analogRead(_pin))/2;
+      value = (value + _readADC(_pin))/2;
     }
     sum += (value - _midPoint);
   }
@@ -227,7 +233,7 @@ uint16_t ACS712::autoMidPoint(float frequency, uint16_t cycles)
     uint32_t start    = micros();
     while (micros() - start < twoPeriods)
     {
-      uint16_t reading = analogRead(_pin);
+      uint16_t reading = _readADC(_pin);
       subTotal += reading;
       samples++;
       //  Delaying prevents overflow
@@ -323,14 +329,14 @@ float ACS712::detectFrequency(float minimalFrequency)
 {
   int maximum = 0;
   int minimum = 0;
-  maximum = minimum = analogRead(_pin);
+  maximum = minimum = _readADC(_pin);
 
   //  determine maxima
   uint32_t timeOut = round(1000000.0 / minimalFrequency);
   uint32_t start = micros();
   while (micros() - start < timeOut)
   {
-    int value = analogRead(_pin);
+    int value = _readADC(_pin);
     if (value > maximum) maximum = value;
     if (value < minimum) minimum = value;
   }
@@ -346,13 +352,13 @@ float ACS712::detectFrequency(float minimalFrequency)
   timeOut *= 10;
   start = micros();
   //  casting to int to keep compiler happy.
-  while ((int(analogRead(_pin)) >  Q1) && ((micros() - start) < timeOut));
-  while ((int(analogRead(_pin)) <= Q3) && ((micros() - start) < timeOut));
+  while ((int(_readADC(_pin)) >  Q1) && ((micros() - start) < timeOut));
+  while ((int(_readADC(_pin)) <= Q3) && ((micros() - start) < timeOut));
   start = micros();
   for (int i = 0; i < 10; i++)
   {
-    while ((int(analogRead(_pin)) >  Q1) && ((micros() - start) < timeOut));
-    while ((int(analogRead(_pin)) <= Q3) && ((micros() - start) < timeOut));
+    while ((int(_readADC(_pin)) >  Q1) && ((micros() - start) < timeOut));
+    while ((int(_readADC(_pin)) <= Q3) && ((micros() - start) < timeOut));
   }
   uint32_t stop = micros();
 
@@ -380,13 +386,13 @@ float ACS712::getMicrosAdjust()
 //  DEBUG
 uint16_t ACS712::getMinimum(uint16_t milliSeconds)
 {
-  uint16_t minimum = analogRead(_pin);
+  uint16_t minimum = _readADC(_pin);
 
   //  find minimum
   uint32_t start = millis();
   while (millis() - start < milliSeconds)
   {
-    uint16_t value = analogRead(_pin);
+    uint16_t value = _readADC(_pin);
     if (value < minimum) minimum = value;
   }
   return minimum;
@@ -395,18 +401,29 @@ uint16_t ACS712::getMinimum(uint16_t milliSeconds)
 
 uint16_t ACS712::getMaximum(uint16_t milliSeconds)
 {
-  uint16_t maximum = analogRead(_pin);
+  uint16_t maximum = _readADC(_pin);
 
   //  find minimum
   uint32_t start = millis();
   while (millis() - start < milliSeconds)
   {
-    uint16_t value = analogRead(_pin);
+    uint16_t value = _readADC(_pin);
     if (value > maximum) maximum = value;
   }
   return maximum;
 }
 
 
+void ACS712::setADC(uint16_t (* f)(uint8_t), float volts, uint16_t maxADC)
+{
+  _readADC = f;
+
+  _maxADC      = maxADC;
+  _mVperStep   = 1000.0 * volts / maxADC;  //  1x 1000 for V -> mV
+  _mAPerStep   = 1000.0 * _mVperStep / _mVperAmpere;
+  _midPoint    = maxADC / 2;
+}
+
+
 // -- END OF FILE --
 

ACS712.h

@@ -2,7 +2,7 @@
 //
 //    FILE: ACS712.h
 //  AUTHOR: Rob Tillaart, Pete Thompson
-// VERSION: 0.3.3
+// VERSION: 0.3.4
 //    DATE: 2020-08-02
 // PURPOSE: ACS712 library - current measurement
 //     URL: https://github.com/RobTillaart/ACS712
@@ -13,7 +13,7 @@
 
 #include "Arduino.h"
 
-#define ACS712_LIB_VERSION        (F("0.3.3"))
+#define ACS712_LIB_VERSION        (F("0.3.4"))
 
 
 //  ACS712_FF_SINUS == 1.0/sqrt(2) == 0.5 * sqrt(2)
@@ -105,6 +105,9 @@ class ACS712
     uint16_t getMaximum(uint16_t milliSeconds = 20);
 
 
+    //  EXPERIMENTAL 0.3.4
+    void setADC(uint16_t (*)(uint8_t), float volts, uint16_t maxADC);
+
   private:
     uint8_t   _pin;
     uint16_t  _maxADC;
@@ -116,16 +119,20 @@ class ACS712
     uint8_t   _noisemV;
     float     _microsAdjust   = 1.0;  //  0.9986
     bool      _suppresNoise = false;
+
+    //  EXPERIMENTAL 0.3.4
+    //  supports up to 16 bits ADC.
+    uint16_t (* _readADC)(uint8_t);
 };
 
 
-// simulate analogRead() - develop only -
-// static int aRead(uint8_t pin)
-// {
-  // float t = micros();
-  // float value = 515 + 50 * sin(t * PI / 180.0);
-  // return value;
-// }
+//  wrapper for internal analogRead()
+//  solves platform specific casting.
+static uint16_t _internalAnalog(uint8_t pin)
+{
+  return analogRead(pin);
+}
+
 
 // -- END OF FILE --
 

CHANGELOG.md

@@ -6,13 +6,19 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
-## [0.3.3] - 2023-03-01
+## [0.3.4] - 2023-01-14
+- experimental
+- add **void setADC()** to use an external ADC for measurements.
+- add **static uint16_t internalAnalog(uint8_t p)** wrapping analogRead() - solves casting.
+- add example ACS712_20_DC_external_ADC.ino
+
+
+## [0.3.3] - 2023-01-03
 - update GitHub actions
 - update license
 - add example
 - add URL in .h .cpp
 
-
 ## [0.3.2] - 2022-11-18
 - fix #26 revert data type \_midPoint to int
 - Add CHANGELOG.md

README.md

@@ -218,7 +218,6 @@ float formFactor = 2.0 * mA_AC_sampling() / ACS.mA_peak2peak();
 See - ACS712_20_determine_form_factor.ino
 
 
-
 #### Noise
 
 Default = 21 mV (datasheet)
@@ -274,6 +273,23 @@ Testing with my UNO I got a factor 0.9986.
 Current version is experimental and not performance optimized. 
 
 
+#### setADC (experimental 0.3.4)
+
+- **void setADC(uint16_t (\*)(uint8_t), float volts, uint16_t maxADC)** sets the ADC function and its parameters.
+Defaults the internal **analogRead()** by this wrapper in ACS712.h:
+```cpp
+static uint16_t _internalAnalog(uint8_t pin)
+{
+  return analogRead(pin);
+}
+```
+
+Be sure to set the parameters of the constructor correctly.
+
+- example ACS712_20_DC_external_ADC.ino
+- https://github.com/RobTillaart/ACS712/issues/31
+
+
 ## Voltage divider
 
 As per issue #15 in which an ACS712 was connected via a voltage divider to the ADC of an ESP32.

examples/ACS712_20_DC_external_ADC/ACS712_20_DC_external_ADC.ino

@@ -0,0 +1,57 @@
+//
+//    FILE: ACS712_20_DC_external_ADC.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo to measure mA DC with external ADC
+//     URL: https://github.com/RobTillaart/ACS712
+
+//  use with Arduino Serial Plotter
+
+#include "ACS712.h"
+
+
+//  Arduino UNO has 5.0 volt with a max ADC value of 1023 steps
+//  ACS712 5A  uses 185 mV per A
+//  ACS712 20A uses 100 mV per A
+//  ACS712 30A uses  66 mV per A
+
+
+ACS712  ACS(A0, 5.0, 1023, 100);
+//  ESP 32 example (might requires resistors to step down the logic voltage)
+//  ACS712  ACS(25, 3.3, 4095, 185);
+
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial);
+  Serial.println(__FILE__);
+  Serial.print("ACS712_LIB_VERSION: ");
+  Serial.println(ACS712_LIB_VERSION);
+
+  ACS.setADC(testADC, 10, 1023);
+
+  //  ACS.autoMidPoint();
+  //  Serial.println(ACS.getMidPoint());
+}
+
+
+void loop()
+{
+  int mA = ACS.mA_DC();
+  Serial.println(mA);
+  delay(1000);
+}
+
+//  wrapper needed for external analogRead()
+//  as casting behavior is undefined between different function signatures.
+uint16_t testADC(uint8_t p)
+{
+  //  simulation
+  return 600 + p;
+  //  replace with an external ADC call.
+  //  return ADS.readADC(p);
+  //  return analogRead(p + 1);  // use another internal ADC
+}
+
+
+// -- END OF FILE --

keywords.txt

@@ -36,9 +36,12 @@ getMicrosAdjust	KEYWORD2
 getMinimum	KEYWORD2
 getMaximum	KEYWORD2
 
+setADC	KEYWORD2
+
 
 # Constants (LITERAL1)
 ACS712_LIB_VERSION	LITERAL1
+
 ACS712_FF_SINUS	LITERAL1
 ACS712_FF_SQUARE	LITERAL1
 ACS712_FF_TRIANGLE	LITERAL1

library.json

@@ -21,7 +21,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/ACS712.git"
   },
-  "version": "0.3.3",
+  "version": "0.3.4",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",

library.properties

@@ -1,5 +1,5 @@
 name=ACS712
-version=0.3.3
+version=0.3.4
 author=Rob Tillaart <[email protected]>, Pete Thompson <[email protected]>
 maintainer=Rob Tillaart <[email protected]>
 sentence=ACS712 library for Arduino.