Fix #44, byte order 16 bits API (#45)

- fix #44, add function to reverse the byte order of the 16 bit API.
- update readme.md

Author: RobTillaart

CHANGELOG.md

@@ -6,6 +6,12 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.9.0] - 2025-02-18
+- fix #44, add function to reverse the byte order of the 16 bit API.
+- update readme.md
+
+----
+
 ## [0.8.1] - 2025-01-20
 - Add PR #41 interrupt functions. Thanks to Klang
 - add link to keypad library

MCP23017.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: MCP23017.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.8.1
+// VERSION: 0.9.0
 // PURPOSE: Arduino library for I2C MCP23017 16 channel port expander
 //    DATE: 2019-10-12
 //     URL: https://github.com/RobTillaart/MCP23017_RT
@@ -60,6 +60,12 @@ uint8_t MCP23017::getAddress()
 }
 
 
+void MCP23017::reverse16ByteOrder(bool reverse)
+{
+  _reverse16ByteOrder = reverse;
+}
+
+
 ///////////////////////////////////////////////////////////////////
 //
 //  single pin interface
@@ -871,6 +877,11 @@ bool MCP23017::writeReg16(uint8_t reg, uint16_t value)
     return false;
   }
 
+  if (_reverse16ByteOrder)  //  swap regA and regB
+  {
+    value = (value >> 8) | (value << 8);
+  }
+
 //  start write
   _wire->beginTransmission(_address);
   _wire->write(reg);
@@ -887,8 +898,6 @@ bool MCP23017::writeReg16(uint8_t reg, uint16_t value)
 
 uint16_t MCP23017::readReg16(uint8_t reg)
 {
-  uint16_t rv = 0;
-
   _error = MCP23017_OK;
 
   if (reg > MCP23x17_OLAT_B)
@@ -912,9 +921,14 @@ uint16_t MCP23017::readReg16(uint8_t reg)
     _error = MCP23017_I2C_ERROR;
     return 0;
   }
-  rv = _wire->read() << 8;
-  rv += _wire->read();
-  return rv;
+  uint16_t regA = _wire->read();
+  uint16_t regB = _wire->read();
+
+  if (_reverse16ByteOrder)
+  {
+    return (regB << 8) | regA;
+  }
+  return (regA << 8) | regB;
 }
 
 

MCP23017.h

@@ -2,7 +2,7 @@
 //
 //    FILE: MCP23017.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.8.1
+// VERSION: 0.9.0
 // PURPOSE: Arduino library for I2C MCP23017 16 channel port expander
 //    DATE: 2019-10-12
 //     URL: https://github.com/RobTillaart/MCP23017_RT
@@ -16,7 +16,7 @@
 #include "MCP23x17_registers.h"
 
 
-#define MCP23017_LIB_VERSION              (F("0.8.1"))
+#define MCP23017_LIB_VERSION              (F("0.9.0"))
 
 #define MCP23017_OK                       0x00
 #define MCP23017_PIN_ERROR                0x81
@@ -36,6 +36,11 @@ class MCP23017
   bool     isConnected();
   uint8_t  getAddress();
 
+  //       Fix #44, reverse the byte order of the 16 bit API.
+  //       reverse == false ==> backwards compatible (default)
+  //       reverse == true ==> swaps the A and B byte to be more intuitive.
+  void     reverse16ByteOrder(bool reverse = false); 
+
 
   //       single pin interface
   //       mode = INPUT, OUTPUT, INPUT_PULLUP (= same as INPUT)
@@ -122,6 +127,8 @@ class MCP23017
   bool     writeReg16(uint8_t reg, uint16_t value);
   uint16_t readReg16(uint8_t reg);
 
+  bool     _reverse16ByteOrder = false;
+
   uint8_t   _address;
   TwoWire*  _wire;
   uint8_t   _error;

README.md

@@ -50,6 +50,11 @@ However no priority.
 Note that the MCP23S017 (SPI version) does not have this "feature" for **GPA7** and **GPB7**.
 
 
+## 0.9.0  Breaking change
+
+Fix #44, **reverse16ByteOrder(bool)** is added to reverse the byte order of the 16 bit API.
+Not using or setting the parameter to false keeps the library backwards compatible.
+
 ### 0.8.0 Breaking change
 
 Fix for #47 MCP23S17, bug in enable interrupt handling.
@@ -202,6 +207,12 @@ Returns true if successful.
 
 Please note REVD remarks at top.
 
+Note: since version 0.9.0 a function is added to reverse the byte order of the 16 bit API.
+
+- **void reverse16ByteOrder(bool reverse = false)** reverse the byte order of the 16 bit API.
+Not using this function or setting the parameter to false keeps the library backwards compatible.
+
+
 - **bool pinMode16(uint16_t mask)** mask = 0..0xFFFF, returns true if successful.
 - **bool write16(uint16_t value)** value = 0..0xFFFF, returns true if successful.
 - **uint16_t read16()** reads 16 pins into an uint16_t.

keywords.txt

@@ -9,6 +9,8 @@ begin	KEYWORD2
 isConnected	KEYWORD2
 getAddress	KEYWORD2
 
+reverse16ByteOrder	KEYWORD2
+
 pinMode1	KEYWORD2
 write1	KEYWORD2
 read1	KEYWORD2

library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/MCP23017_RT.git"
   },
-  "version": "0.8.1",
+  "version": "0.9.0",
   "license": "MIT",
   "frameworks": "*",
   "platforms": "*",

library.properties

@@ -1,5 +1,5 @@
 name=MCP23017_RT
-version=0.8.1
+version=0.9.0
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for I2C MCP23017 16 channel port expander  16 IO-lines