From f8e4e34a30169a76b4066c2b8752cc257335d701 Mon Sep 17 00:00:00 2001
From: "Dirk O. Kaar" <dok@dok-net.net>
Date: Sat, 28 May 2022 12:26:29 +0200
Subject: [PATCH 1/3] Add begin() method usual for Arduino driver libs and the
 supporting ctor.

---
 src/MCP23017.cpp | 11 +++++++++++
 src/MCP23017.h   | 12 +++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/MCP23017.cpp b/src/MCP23017.cpp
index b36cb8f..631186f 100644
--- a/src/MCP23017.cpp
+++ b/src/MCP23017.cpp
@@ -5,6 +5,11 @@ MCP23017::MCP23017(uint8_t address, TwoWire& bus) {
 	_bus = &bus;
 }
 
+MCP23017::MCP23017(TwoWire& bus) {
+	_deviceAddr = MCP23017_I2C_ADDRESS;
+	_bus = &bus;
+}
+
 MCP23017::~MCP23017() {}
 
 void MCP23017::init()
@@ -25,6 +30,12 @@ void MCP23017::init()
 	writeRegister(MCP23017Register::GPPU_A, 0xFF, 0xFF);
 }
 
+void MCP23017::begin(uint8_t address)
+{
+	_deviceAddr = address;
+	init();
+}
+
 void MCP23017::portMode(MCP23017Port port, uint8_t directions, uint8_t pullups, uint8_t inverted)
 {
 	writeRegister(MCP23017Register::IODIR_A + port, directions);
diff --git a/src/MCP23017.h b/src/MCP23017.h
index e665108..7ecc372 100644
--- a/src/MCP23017.h
+++ b/src/MCP23017.h
@@ -3,6 +3,7 @@
 #include <Arduino.h>
 #include <Wire.h>
 
+#define MCP23017_I2C_ADDRESS 0x20    ///< The default I2C address of MCP23017.
 #define _MCP23017_INTERRUPT_SUPPORT_ ///< Enables support for MCP23017 interrupts.
 
 enum class MCP23017Port : uint8_t
@@ -65,10 +66,19 @@ class MCP23017
 	 * Instantiates a new instance to interact with a MCP23017 at the specified address.
 	 */
 	MCP23017(uint8_t address, TwoWire& bus = Wire);
+	/**
+	 * Instantiates a new instance to interact with a MCP23017 at the
+	 * MCP23017_I2C_ADDRESS default.
+	 */
+	MCP23017(TwoWire& bus = Wire);
 	~MCP23017();
 #ifdef _DEBUG
 	void debug();
 #endif
+	/**
+	 * May override the I2C address set by the constructor. Implicitly calls init().
+	 */
+	void begin(uint8_t address = MCP23017_I2C_ADDRESS);
 	/**
 	 * Initializes the chip with the default configuration.
 	 * Enables Byte mode (IOCON.BANK = 0 and IOCON.SEQOP = 1).
@@ -221,4 +231,4 @@ class MCP23017
 	void clearInterrupts(uint8_t& portA, uint8_t& portB);
 
 #endif
-};
\ No newline at end of file
+};

From 6e15eedb183161165ac791ff4b87817bfe173073 Mon Sep 17 00:00:00 2001
From: "Dirk O. Kaar" <dok@dok-net.net>
Date: Tue, 31 May 2022 21:47:23 +0200
Subject: [PATCH 2/3] Begin without address argument shall use the ctor
 provided address, not reset it.

---
 src/MCP23017.cpp | 5 +++++
 src/MCP23017.h   | 8 ++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/MCP23017.cpp b/src/MCP23017.cpp
index 631186f..8530e05 100644
--- a/src/MCP23017.cpp
+++ b/src/MCP23017.cpp
@@ -30,6 +30,11 @@ void MCP23017::init()
 	writeRegister(MCP23017Register::GPPU_A, 0xFF, 0xFF);
 }
 
+void MCP23017::begin()
+{
+	init();
+}
+
 void MCP23017::begin(uint8_t address)
 {
 	_deviceAddr = address;
diff --git a/src/MCP23017.h b/src/MCP23017.h
index 7ecc372..a4a9067 100644
--- a/src/MCP23017.h
+++ b/src/MCP23017.h
@@ -76,9 +76,13 @@ class MCP23017
 	void debug();
 #endif
 	/**
-	 * May override the I2C address set by the constructor. Implicitly calls init().
+	 * Uses the I2C address set during construction. Implicitly calls init().
 	 */
-	void begin(uint8_t address = MCP23017_I2C_ADDRESS);
+	void begin();
+	/**
+	 * Overrides the I2C address set by the constructor. Implicitly calls init().
+	 */
+	void begin(uint8_t address);
 	/**
 	 * Initializes the chip with the default configuration.
 	 * Enables Byte mode (IOCON.BANK = 0 and IOCON.SEQOP = 1).

From d5de9ded15c7c470570c23bacb9ac86a360b5d90 Mon Sep 17 00:00:00 2001
From: "Dirk O. Kaar" <19971886+dok-net@users.noreply.github.com>
Date: Thu, 2 Jun 2022 22:47:58 +0200
Subject: [PATCH 3/3] Apply suggestions from code review

Cascade from `begin` with I2C address argument to `begin` w/o argument, it's clearer than calling `init()` from both places.

Co-authored-by: Bertrand Lemasle <blemasle@gmail.com>
---
 src/MCP23017.cpp | 2 +-
 src/MCP23017.h   | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/MCP23017.cpp b/src/MCP23017.cpp
index 8530e05..edd69cd 100644
--- a/src/MCP23017.cpp
+++ b/src/MCP23017.cpp
@@ -38,7 +38,7 @@ void MCP23017::begin()
 void MCP23017::begin(uint8_t address)
 {
 	_deviceAddr = address;
-	init();
+	begin();
 }
 
 void MCP23017::portMode(MCP23017Port port, uint8_t directions, uint8_t pullups, uint8_t inverted)
diff --git a/src/MCP23017.h b/src/MCP23017.h
index a4a9067..3427261 100644
--- a/src/MCP23017.h
+++ b/src/MCP23017.h
@@ -80,7 +80,8 @@ class MCP23017
 	 */
 	void begin();
 	/**
-	 * Overrides the I2C address set by the constructor. Implicitly calls init().
+	 * Overrides the I2C address set by the constructor. Implicitly calls begin().
+
 	 */
 	void begin(uint8_t address);
 	/**