add autoMidPointDC() (#36)

- add **autoMidPointDC(cycles)** see issue #35
- add rounding to **autoMidPoint()**
- update README.md

ACS712.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: ACS712.cpp
 //  AUTHOR: Rob Tillaart, Pete Thompson
-// VERSION: 0.3.5
+// VERSION: 0.3.6
 //    DATE: 2020-08-02
 // PURPOSE: ACS712 library - current measurement
 //     URL: https://github.com/RobTillaart/ACS712
@@ -242,7 +242,20 @@ uint16_t ACS712::autoMidPoint(float frequency, uint16_t cycles)
     }
     total += (subTotal / samples);
   }
-  _midPoint = total / cycles;
+  _midPoint = (total + (cycles/2))/ cycles;    //  rounding.
+  return _midPoint;
+}
+
+
+uint16_t ACS712::autoMidPointDC(uint16_t cycles)
+{
+  if (cycles == 0) cycles = 1;
+  uint32_t total = 0;
+  for (uint16_t i = 0; i < cycles; i++)
+  {
+    total += analogRead(_pin);
+  }
+  _midPoint = (total + (cycles/2))/ cycles;    //  rounding.
   return _midPoint;
 }
 

ACS712.h

@@ -2,7 +2,7 @@
 //
 //    FILE: ACS712.h
 //  AUTHOR: Rob Tillaart, Pete Thompson
-// VERSION: 0.3.5
+// VERSION: 0.3.6
 //    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("0.3.5"))
+#define ACS712_LIB_VERSION        (F("0.3.6"))
 
 
 //  ACS712_FF_SINUS == 1.0/sqrt(2) == 0.5 * sqrt(2)
@@ -68,7 +68,10 @@ class ACS712
     uint16_t incMidPoint();
     uint16_t decMidPoint();
     //  Auto midPoint, assuming zero DC current or any AC current
+    //  For DC current set the frequency to 1000 or so to reduce blocking.
     uint16_t autoMidPoint(float frequency = ACS712_DEFAULT_FREQ, uint16_t cycles = 1);
+    //  Auto midPoint, dedicated for zero DC current (much faster ==> less blocking)
+    uint16_t autoMidPointDC(uint16_t cycles = 1);
     //  resets to half maxADC
     uint16_t resetMidPoint();
 
@@ -106,8 +109,10 @@ class ACS712
 
 
     //  EXPERIMENTAL 0.3.4
+    //  function returning 16 bit max, with pin or channel as parameter
     void setADC(uint16_t (*)(uint8_t), float volts, uint16_t maxADC);
 
+
   private:
     uint8_t   _pin;
     uint16_t  _maxADC;

CHANGELOG.md

@@ -6,13 +6,18 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.3.6] - 2023-04-19
+- add **autoMidPointDC(cycles)** see issue #35
+- add rounding to **autoMidPoint()**
+- update README.md
+
+
 ## [0.3.5] - 2023-01-18
 - fix #33 failing build => issue 345 created @ arduino-ci
 - redo **setADC()**
 - allows reset to internal **analogRead()** too now.
 - update README.md
 
-
 ## [0.3.4] - 2023-01-14
 - experimental
 - add **void setADC()** to use an external ADC for measurements.

README.md

@@ -151,21 +151,27 @@ Since 0.3.0 all midpoint functions return the actual midPoint.
 
 - **uint16_t setMidPoint(uint16_t midPoint)** sets midpoint for the ADC conversion.
 Parameter must be between 0 and maxADC/2, otherwise midpoint is not changed.
-- **uint16_t autoMidPoint(float frequency = 50, uint16_t cycles = 1)** Auto midPoint,
-assuming zero DC current or any AC current.
-The function takes the average of many measurements during one or more full cycles.
-Note the function therefore blocks for at least 2 periods.
-By increasing the number of cycles the function averages even more measurements,
-possibly resulting in a better midPoint. Idea is that noise will average out.
-This function is mandatory for measuring AC.
-  - 0.2.2 frequencies other than 50 and 60 are supported.
-  - 0.2.8 the parameter cycles allow to average over a number of cycles.
 - **uint16_t getMidPoint()** read the value set / determined.
 - **uint16_t incMidPoint()** manual increase midpoint, e.g. useful in an interactive application.
 Will not increase if midpoint equals macADC.
 - **uint16_t decMidPoint()** manual decrease midpoint.
 Will not decrease if midpoint equals 0.
 - **uint16_t resetMidPoint()** resets the midpoint to the initial value of maxADC / 2 as in the constructor.
+- **uint16_t autoMidPointDC(uint16_t cycles = 1)** Auto midPoint for DC only.
+Assuming zero DC current. To reduce the noise cycles must be increased even up to 100.
+This method is typically much faster for DC than the **autoMidPoint(freq, cycles)** 
+for the same number of cycles. (See issue #35)
+- **uint16_t autoMidPoint(float frequency = 50, uint16_t cycles = 1)** Auto midPoint, for any AC current or zero DC current.  
+For DC one can use a high frequency e.g. 1000 Hz to reduce the time blocking.
+The function takes the average of many measurements during one or more full cycles.
+Note the function therefore blocks for at least 2 periods which is about 
+40 ms for 50 Hz.
+By increasing the number of cycles the function averages even more measurements,
+possibly resulting in a better midPoint. Idea is that noise will average out.
+This function is mandatory for measuring AC.
+  - 0.2.2 frequencies other than 50 and 60 are supported.
+  - 0.2.8 the parameter cycles allow to average over a number of cycles.
+
 
 Since version 0.3.0 there is another way to determine the midPoint.
 One can use the two debug functions.
@@ -393,23 +399,34 @@ The examples show the basic working of the functions.
 
 #### Must
 
+- test more
+  - other than the 20A module
+  - 5, 10, 30, 50 ...
+  - need to buy extra hardware
+
 
 #### Should - 0.3.x
 
+- investigate **estimateMidPoint(confidence)** See issue #35
+  - is less blocking by spreading the sampling over many calls.
+    returning a confidence level.
 - investigate noise suppression  #21 (0.3.1 and later)
 - investigate blocking calls:
   - **mA_AC()** blocks for about 20 ms at 50 Hz.
   This might affect task scheduling on a ESP32. Needs to be investigated.
   Probably need a separate thread that wakes up when new analogRead is available?
   - RTOS specific class?
-  - **detectFrequency(float)** blocks pretty long.
+- investigate **detectFrequency(float)** blocks pretty long.
 
 
 #### Could
 
 - merge **mA_AC()** and **mA_AC_sampling()** into one. (0.4.0)
   - or remove - depreciate - the worst one
 - add range check to (all) set functions?
+- add unit test for **autoMidPointDC()** (needed?)
+- **setMidPoint()**
+  - Q: could midpoint be set beyond maxADC? is there any use case?
 
 
 #### Won't (unless requested)

examples/ACS712_autoMidPointDC/ACS712_autoMidPointDC.ino

@@ -0,0 +1,54 @@
+//
+//    FILE: ACS712_autoMidPointDC.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo detect DC midpoint.
+//     URL: https://github.com/RobTillaart/ACS712
+
+
+#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);
+
+
+uint32_t start, stop;
+
+uint16_t midPoint = 0;
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial);
+  Serial.println(__FILE__);
+  Serial.print("ACS712_LIB_VERSION: ");
+  Serial.println(ACS712_LIB_VERSION);
+  delay(10);
+
+  //  might be different 1 cycle or 100.
+  start = micros();
+  midPoint = ACS.autoMidPointDC(1);
+  stop = micros();
+  Serial.println("ACS.autoMidPointDC()");
+  Serial.print("us:\t");
+  Serial.println(stop - start);
+  Serial.print("MP 1:\t");
+  Serial.println(midPoint);
+
+  midPoint = ACS.autoMidPointDC(100);
+  Serial.print("MP 100:\t");
+  Serial.println(midPoint);
+}
+
+
+void loop()
+{
+}
+
+
+//  -- END OF FILE --

keywords.txt

@@ -15,6 +15,7 @@ incMidPoint	KEYWORD2
 decMidPoint	KEYWORD2
 resetMidPoint	KEYWORD2
 autoMidPoint	KEYWORD2
+autoMidPointDC	KEYWORD2
 
 setFormFactor	KEYWORD2
 getFormFactor	KEYWORD2

library.json

@@ -21,7 +21,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/ACS712.git"
   },
-  "version": "0.3.5",
+  "version": "0.3.6",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",

library.properties

@@ -1,5 +1,5 @@
 name=ACS712
-version=0.3.5
+version=0.3.6
 author=Rob Tillaart <[email protected]>, Pete Thompson <[email protected]>
 maintainer=Rob Tillaart <[email protected]>
 sentence=ACS712 library for Arduino.

test/unit_test_001.cpp

@@ -212,4 +212,4 @@ unittest(test_AmperePerStep)
 unittest_main()
 
 
-// -- END OF FILE --
+//  -- END OF FILE --