add INA226_MINIMAL_SHUNT (#27)

- add constant INA226_MINIMAL_SHUNT
RobTillaart · May 24, 2023 · 1f97226 · 1f97226
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -6,8 +6,11 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
-## [0.4.2] - 2023-04-03
+## [0.4.3] - 2023-05-07
+- add constant INA226_MINIMAL_SHUNT
+
 
+## [0.4.2] - 2023-04-03
 - added **getBusVoltage_uV()** for completeness
 - INA226_test_I2C.ino to prep performance tests
 - fix changelog.md
@@ -17,7 +20,6 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - update license 2023
 - minor edits
 
-
 ## [0.4.1] - 2022-11-12
 - Add RP2040 support to build-CI.
 - Add CHANGELOG.md, replaces release_notes to be consistent over my libraries.

diff --git a/INA226.cpp b/INA226.cpp
@@ -1,6 +1,6 @@
 //    FILE: INA226.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.4.2
+// VERSION: 0.4.3
 //    DATE: 2021-05-18
 // PURPOSE: Arduino library for INA226 power sensor
 //     URL: https://github.com/RobTillaart/INA226
@@ -195,9 +195,9 @@ int INA226::setMaxCurrentShunt(float maxCurrent, float shunt, bool normalize)
   //  fix #16 - datasheet 6.5 Electrical Characteristics
   //            rounded value to 80 mV
   float shuntVoltage = abs(maxCurrent * shunt);
-  if (shuntVoltage > 0.080) return INA226_ERR_SHUNTVOLTAGE_HIGH;
-  if (maxCurrent < 0.001)   return INA226_ERR_MAXCURRENT_LOW;
-  if (shunt < 0.001)        return INA226_ERR_SHUNT_LOW;
+  if (shuntVoltage > 0.080)         return INA226_ERR_SHUNTVOLTAGE_HIGH;
+  if (maxCurrent < 0.001)           return INA226_ERR_MAXCURRENT_LOW;
+  if (shunt < INA226_MINIMAL_SHUNT) return INA226_ERR_SHUNT_LOW;
 
   _current_LSB = maxCurrent * 3.0517578125e-5;      // maxCurrent / 32768;
 

diff --git a/INA226.h b/INA226.h
@@ -1,7 +1,7 @@
 #pragma once
 //    FILE: INA226.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.4.2
+// VERSION: 0.4.3
 //    DATE: 2021-05-18
 // PURPOSE: Arduino library for INA226 power sensor
 //     URL: https://github.com/RobTillaart/INA226
@@ -14,7 +14,7 @@
 #include "Wire.h"
 
 
-#define INA226_LIB_VERSION              (F("0.4.2"))
+#define INA226_LIB_VERSION              (F("0.4.3"))
 
 
 //  set by setAlertRegister
@@ -39,6 +39,9 @@
 #define INA226_ERR_SHUNT_LOW             0x8002
 
 
+//  See issue #26
+#define INA226_MINIMAL_SHUNT             (0.001)
+
 
 class INA226
 {

diff --git a/README.md b/README.md
@@ -287,6 +287,26 @@ The alert line falls when alert is reached.
 - **uint16_t getRegister(uint8_t reg)** fetch registers directly, for debugging only.
 
 
+## Adjusting the range of the INA226
+
+**use at own risk**
+In issue #26 a hack is made to scale the INA226 to 300A by using a very small shunt.
+The library has a minimal limit for the shunt of 0.001 ohm.
+This limit can be overruled to support other ranges like the one discussed in #26.
+Overruling can be done by patching the following value in the INA226.h file.
+
+```cpp
+#define INA226_MINIMAL_SHUNT             (0.001)
+```
+
+Be aware that
+- **you should NOT do this unless you understand the implications**.
+- you do this at your own risk.
+- the resistance of wires used affect measurements with very small shunts.
+- solder might change the resistance too.
+- you do this at your own risk.
+
+
 ## Operational
 
 See examples.. 

diff --git a/keywords.txt b/keywords.txt
@@ -82,3 +82,6 @@ INA226_ERR_SHUNTVOLTAGE_HIGH	LITERAL1
 INA226_ERR_MAXCURRENT_LOW	LITERAL1
 INA226_ERR_SHUNT_LOW	LITERAL1
 
+INA226_MINIMAL_SHUNT	LITERAL1
+
+
diff --git a/library.json b/library.json
@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/INA226.git"
   },
-  "version": "0.4.2",
+  "version": "0.4.3",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",

diff --git a/library.properties b/library.properties
@@ -1,5 +1,5 @@
 name=INA226
-version=0.4.2
+version=0.4.3
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for INA226 power sensor

diff --git a/test/unit_test_001.cpp b/test/unit_test_001.cpp
@@ -78,6 +78,8 @@ unittest(test_constants)
   assertEqual(0x8000, INA226_ERR_SHUNTVOLTAGE_HIGH);
   assertEqual(0x8001, INA226_ERR_MAXCURRENT_LOW);
   assertEqual(0x8002, INA226_ERR_SHUNT_LOW);
+
+  assertEqualFloat(0.001, INA226_MINIMAL_SHUNT, 0.0001);
 }
Original file line number	Diff line number	Diff line change
Expand Up		@@ -82,3 +82,6 @@ INA226_ERR_SHUNTVOLTAGE_HIGH LITERAL1
		INA226_ERR_MAXCURRENT_LOW LITERAL1
		INA226_ERR_SHUNT_LOW LITERAL1

		INA226_MINIMAL_SHUNT LITERAL1