From 59e0897b725c30b3e24046620683a1c857d42d63 Mon Sep 17 00:00:00 2001
From: John Jones <john@johnjonesfour.com>
Date: Tue, 16 Dec 2025 18:59:38 -0500
Subject: [PATCH] Added support for other GPIO providers such as
 Adafruit_MCP23XXX

---
 .gitignore            |  1 +
 platformio.ini        | 10 ++++++++++
 src/RotaryEncoder.cpp | 45 ++++++++++++++++++++++++++++++++++++-------
 src/RotaryEncoder.h   | 28 +++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 7 deletions(-)
 create mode 100644 platformio.ini

diff --git a/.gitignore b/.gitignore
index 7461aa1..88761ee 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 .vscode/*
 _*
+.pio
\ No newline at end of file
diff --git a/platformio.ini b/platformio.ini
new file mode 100644
index 0000000..d394733
--- /dev/null
+++ b/platformio.ini
@@ -0,0 +1,10 @@
+[platformio]
+default_envs = uno
+
+[env:uno]
+platform = atmelavr
+board = uno
+framework = arduino
+
+lib_deps =
+	adafruit/Adafruit MCP23017 Arduino Library@^2.3.2
\ No newline at end of file
diff --git a/src/RotaryEncoder.cpp b/src/RotaryEncoder.cpp
index 6a3dd9c..6463f4f 100644
--- a/src/RotaryEncoder.cpp
+++ b/src/RotaryEncoder.cpp
@@ -15,6 +15,31 @@
 #include "RotaryEncoder.h"
 #include "Arduino.h"
 
+void BuiltInInputProvider::pinMode(uint8_t pin, uint8_t mode)
+{
+  pinMode(pin, mode);
+}
+
+int BuiltInInputProvider::digitalRead(uint8_t pin)
+{
+  return digitalRead(pin);
+}
+
+MCP23XXXInputProvider::MCP23XXXInputProvider(Adafruit_MCP23XXX *mcp)
+{
+  this->mcp = mcp;
+}
+
+void MCP23XXXInputProvider::pinMode(uint8_t pin, uint8_t mode)
+{
+  this->mcp->pinMode(pin, mode);
+}
+
+int MCP23XXXInputProvider::digitalRead(uint8_t pin)
+{
+  return this->mcp->digitalRead(pin);
+}
+
 #define LATCH0 0 // input state at position 0
 #define LATCH3 3 // input state at position 3
 
@@ -38,8 +63,10 @@ const int8_t KNOBDIR[] = {
 
 // ----- Initialization and Default Values -----
 
-RotaryEncoder::RotaryEncoder(int pin1, int pin2, LatchMode mode)
+RotaryEncoder::RotaryEncoder(InputProvider *provider, int pin1, int pin2, LatchMode mode = LatchMode::FOUR0)
 {
+  this->provider = provider;
+
   int sig1 = 0;
   int sig2 = 0;
 
@@ -50,11 +77,11 @@ RotaryEncoder::RotaryEncoder(int pin1, int pin2, LatchMode mode)
 
   // Setup the input pins and turn on pullup resistor
   if ((pin1 >= 0) && (pin2 >= 0)) {
-    pinMode(pin1, INPUT_PULLUP);
-    pinMode(pin2, INPUT_PULLUP);
+    this->provider->pinMode(pin1, INPUT_PULLUP);
+    this->provider->pinMode(pin2, INPUT_PULLUP);
     // when not started in motion, the current state of the encoder should be 3
-    sig1 = digitalRead(_pin1);
-    sig2 = digitalRead(_pin2);
+    sig1 = this->provider->digitalRead(_pin1);
+    sig2 = this->provider->digitalRead(_pin2);
   }
   
   _oldState = sig1 | (sig2 << 1);
@@ -66,6 +93,10 @@ RotaryEncoder::RotaryEncoder(int pin1, int pin2, LatchMode mode)
 } // RotaryEncoder()
 
 
+RotaryEncoder::RotaryEncoder(int pin1, int pin2, LatchMode mode = LatchMode::FOUR0) : RotaryEncoder(new BuiltInInputProvider(), pin1, pin2, mode) {}
+
+RotaryEncoder::RotaryEncoder(Adafruit_MCP23XXX *mcp, int pin1, int pin2, LatchMode mode = LatchMode::FOUR0) : RotaryEncoder(new MCP23XXXInputProvider(mcp), pin1, pin2, mode) {}
+
 long RotaryEncoder::getPosition()
 {
   return _positionExt;
@@ -116,8 +147,8 @@ void RotaryEncoder::setPosition(long newPosition)
 // Slow, but Simple Variant by directly Read-Out of the Digital State within loop-call
 void RotaryEncoder::tick(void)
 {
-  int sig1 = digitalRead(_pin1);
-  int sig2 = digitalRead(_pin2);
+  int sig1 = this->provider->digitalRead(_pin1);
+  int sig2 = this->provider->digitalRead(_pin2);
   tick(sig1, sig2);
 } // tick()
 
diff --git a/src/RotaryEncoder.h b/src/RotaryEncoder.h
index 324bf4d..e198f45 100644
--- a/src/RotaryEncoder.h
+++ b/src/RotaryEncoder.h
@@ -20,6 +20,30 @@
 #define RotaryEncoder_h
 
 #include "Arduino.h"
+#include <Adafruit_MCP23XXX.h>
+
+class InputProvider
+{
+public:
+  virtual void pinMode(uint8_t pin, uint8_t mode) = 0;
+  virtual int digitalRead(uint8_t pin) = 0;
+};
+
+class BuiltInInputProvider : public InputProvider
+{
+public:
+  void pinMode(uint8_t pin, uint8_t mode);
+  int digitalRead(uint8_t pin);
+};
+
+class MCP23XXXInputProvider : public InputProvider
+{
+public:
+  MCP23XXXInputProvider(Adafruit_MCP23XXX *mcp);
+  Adafruit_MCP23XXX *mcp;
+  void pinMode(uint8_t pin, uint8_t mode);
+  int digitalRead(uint8_t pin);
+};
 
 class RotaryEncoder
 {
@@ -37,6 +61,8 @@ class RotaryEncoder
   };
 
   // ----- Constructor -----
+  RotaryEncoder(InputProvider *provider, int pin1, int pin2, LatchMode mode = LatchMode::FOUR0);
+  RotaryEncoder(Adafruit_MCP23XXX *mcp, int pin1, int pin2, LatchMode mode = LatchMode::FOUR0);
   RotaryEncoder(int pin1, int pin2, LatchMode mode = LatchMode::FOUR0);
 
   // retrieve the current position
@@ -75,6 +101,8 @@ class RotaryEncoder
 
   unsigned long _positionExtTime;     // The time the last position change was detected.
   unsigned long _positionExtTimePrev; // The time the previous position change was detected.
+
+  InputProvider *provider;
 };
 
 #endif