Add support for input shift registers (e.g. 74HC165)

_Boards/Atmel/Board_Mega/MFBoards.h

@@ -19,6 +19,9 @@
 #ifndef MF_SHIFTER_SUPPORT
 #define MF_SHIFTER_SUPPORT 1
 #endif
+#ifndef MF_INPUT_SHIFTER_SUPPORT
+#define MF_INPUT_SHIFTER_SUPPORT 1
+#endif
 
 #define MODULE_MAX_PINS 69
 #define MAX_OUTPUTS 40
@@ -30,6 +33,7 @@
 #define MAX_MFLCD_I2C 2
 #define MAX_ANALOG_INPUTS 5
 #define MAX_SHIFTERS 10
+#define MAX_INPUT_SHIFTERS 10
 
 #define STEPS 64
 #define STEPPER_SPEED 400 // 300 already worked, 467, too?

_Boards/Atmel/Board_ProMicro/MFBoards.h

@@ -19,6 +19,9 @@
 #ifndef MF_SHIFTER_SUPPORT
 #define MF_SHIFTER_SUPPORT 1
 #endif
+#ifndef MF_INPUT_SHIFTER_SUPPORT
+#define MF_INPUT_SHIFTER_SUPPORT 1
+#endif
 
 #define MODULE_MAX_PINS 21
 #define MAX_OUTPUTS 10
@@ -30,6 +33,7 @@
 #define MAX_MFLCD_I2C 2
 #define MAX_ANALOG_INPUTS 2
 #define MAX_SHIFTERS 4
+#define MAX_INPUT_SHIFTERS 4
 
 #define STEPS 64
 #define STEPPER_SPEED 400 // 300 already worked, 467, too?

_Boards/Atmel/Board_Uno/MFBoards.h

@@ -19,6 +19,9 @@
 #ifndef MF_SHIFTER_SUPPORT
 #define MF_SHIFTER_SUPPORT 1
 #endif
+#ifndef MF_INPUT_SHIFTER_SUPPORT
+#define MF_INPUT_SHIFTER_SUPPORT 1
+#endif
 
 #define MODULE_MAX_PINS 13
 #define MAX_OUTPUTS 8
@@ -30,6 +33,7 @@
 #define MAX_MFLCD_I2C 2
 #define MAX_ANALOG_INPUTS 0
 #define MAX_SHIFTERS 0
+#define MAX_INPUT_SHIFTERS 4
 
 #define STEPS 64
 #define STEPPER_SPEED 400 // 300 already worked, 467, too?

include/MFInputShifter.h

@@ -0,0 +1,56 @@
+// MFInputShifter.h
+
+#ifndef MFInputShifter_h
+#define MFInputShifter_h
+
+#if ARDUINO >= 100
+#include <Arduino.h>
+#else
+#include <WProgram.h>
+#include <wiring.h>
+#endif
+
+// Maximum number of shifters allowed on an individual chain. While this is currently set to 4
+// there is no technical limit in the code for how many can be chained. It is constrained only
+// by available memory (one byte required per chip) and the time it takes to read all the bits in.
+#define MAX_CHAINED_INPUT_SHIFTERS 4
+
+extern "C"
+{
+  typedef void (*inputShifterEvent)(byte, uint8_t, const char *);
+};
+
+enum
+{
+  inputShifterOnPress,
+  inputShifterOnRelease,
+};
+
+/////////////////////////////////////////////////////////////////////
+/// \class MFInputShifter MFInputShifter.h <MFInputShifter.h>
+class MFInputShifter
+{
+public:
+  MFInputShifter(const char *name = "InputShifter");
+  void attach(uint8_t latchPin, uint8_t clockPin, uint8_t dataPin, uint8_t moduleCount);
+  void detach();
+  void clear();
+  void update();
+  void attachHandler(byte eventId, inputShifterEvent newHandler);
+
+private:
+  const char *_name;
+  uint8_t _latchPin;    // SH/~LD (latch) pin
+  uint8_t _clockPin;    // CLK (clock) pin
+  uint8_t _dataPin;     // SDO (data) pin
+  uint8_t _moduleCount; // Number of 8 bit modules in series.
+  bool _initialized = false;
+  uint32_t _last;
+  uint8_t _lastState[MAX_CHAINED_INPUT_SHIFTERS];
+
+  void detectChanges(uint8_t lastState, uint8_t currentState, uint8_t module);
+  void trigger(uint8_t pin, bool state);
+  void clearLastState();
+  inputShifterEvent _handlerList[2];
+};
+#endif

include/mobiflight.h

@@ -4,7 +4,7 @@
 #include <MFEncoder.h>
 #include <MFAnalog.h>
 
-#define MF_BUTTON_DEBOUNCE_MS   10      // time between updating the buttons
+#define MF_BUTTON_DEBOUNCE_MS 10 // time between updating the buttons
 
 enum
 {
@@ -19,7 +19,8 @@ enum
   kTypeEncoder,             // 8
   kTypeStepper,             // 9 (new stepper type with auto zero support if btnPin is > 0)
   kShiftRegister,           // 10 Shift register support (example: 74HC595, TLC592X)
-  kTypeAnalogInput          // 11 Analog Device with 1 pin
+  kTypeAnalogInput,         // 11 Analog Device with 1 pin
+  kTypeInputShifter         // 12 Input shift register support (example: 74HC165)
 };
 
 // This is the list of recognized commands. These can be commands that can either be sent or received.
@@ -57,7 +58,8 @@ enum
   kSetLcdDisplayI2C,     // 25
   kSetModuleBrightness,  // 26
   kSetShiftRegisterPins, // 27
-  kAnalogChange          // 28
+  kAnalogChange,         // 28
+  kInputShifterChange    // 29
 };
 
 void attachCommandCallbacks();
@@ -124,6 +126,8 @@ void handlerOnAnalogChange(int value, uint8_t pin, const char *name);
 void OnInitShiftRegister();
 void OnSetShiftRegisterPins();
 void AddShifter(uint8_t latchPin, uint8_t clockPin, uint8_t dataPin, uint8_t modules, char const *name);
-
-
+void AddInputShifter(uint8_t latchPin, uint8_t clockPin, uint8_t dataPin, uint8_t modules, char const *name);
+void ClearInputShifters();
+void readInputShifters();
+void handlerInputShifterOnChange(uint8_t eventId, uint8_t pin, const char *name);
 #endif

src/MF_Modules/MFInputShifter.cpp

@@ -0,0 +1,129 @@
+// MFSegments.cpp
+//
+// Copyright (C) 2021
+#include "MFInputShifter.h"
+
+MFInputShifter::MFInputShifter(const char *name)
+{
+  _initialized = false;
+  clearLastState();
+  _last = millis();
+  _name = name;
+}
+
+// Registers a new input shifter and configures the clock, data and latch pins as well
+// as the number of modules to read from.
+void MFInputShifter::attach(uint8_t latchPin, uint8_t clockPin, uint8_t dataPin, uint8_t moduleCount)
+{
+  _latchPin = latchPin;
+  _clockPin = clockPin;
+  _dataPin = dataPin;
+  _moduleCount = moduleCount;
+
+  pinMode(_latchPin, OUTPUT);
+  pinMode(_clockPin, OUTPUT);
+  pinMode(_dataPin, INPUT);
+  _initialized = true;
+}
+
+// Reads the values from the attached modules, compares them to the previously
+// read values, and calls the registered event handler for any inputs that
+// changed from the previously read state.
+void MFInputShifter::update()
+{
+  // Don't take any changes within the last 10 milliseconds to cover basic switch debouncing.
+  // This technically could miss two different switches changing within 10 milliseconds
+  // but that seems extremely unlikely to happen.
+  uint32_t now = millis();
+  if (now - _last <= 10)
+    return;
+
+  digitalWrite(_clockPin, HIGH); // Preset clock to retrieve first bit
+  digitalWrite(_latchPin, HIGH); // Disable input latching and enable shifting
+
+  // Multiple chained modules are handled one at a time. As shiftIn() keeps getting
+  // called it will pull in the data from each chained module.
+  for (int i = 0; i < _moduleCount; i++)
+  {
+    uint8_t currentState;
+
+    currentState = shiftIn(_dataPin, _clockPin, MSBFIRST);
+
+    // If an input changed on the current module from the last time it was read
+    // then hand it off to figure out which bits specifically changed.
+    if (currentState != _lastState[i])
+    {
+      detectChanges(_lastState[i], currentState, i);
+      _lastState[i] = currentState;
+    }
+  }
+
+  digitalWrite(_latchPin, LOW); // disable shifting and enable input latching
+
+  _last = now;
+}
+
+// Detects changes between the current state and the previously saved state
+// of a byte's worth of input.
+void MFInputShifter::detectChanges(uint8_t lastState, uint8_t currentState, uint8_t module)
+{
+  for (uint8_t i = 0; i < 8; i++)
+  {
+    // If last and current input state for the bit are different
+    // then the input changed and the handler for the bit needs to fire
+    if ((lastState & 1) ^ (currentState & 1))
+    {
+      // When triggering event the pin is the actual pin on the chip offset by 8 bits for each
+      // module beyond the first that it's on. The state of the trigger is the bit currently
+      // in position 0 of currentState.
+      trigger(i + (module * 8), currentState & 1);
+    }
+
+    lastState = lastState >> 1;
+    currentState = currentState >> 1;
+  }
+}
+
+// Triggers the event handler for the associated input shift register pin,
+// if a handler is registered.
+void MFInputShifter::trigger(uint8_t pin, bool state)
+{
+  if (state == LOW && _handlerList[inputShifterOnPress] != NULL)
+  {
+    (*_handlerList[inputShifterOnPress])(inputShifterOnPress, pin, _name);
+  }
+  else if (_handlerList[inputShifterOnRelease] != NULL)
+  {
+    (*_handlerList[inputShifterOnRelease])(inputShifterOnRelease, pin, _name);
+  }
+}
+
+// Attaches a new event handler for the specified event.
+void MFInputShifter::attachHandler(byte eventId, inputShifterEvent newHandler)
+{
+  _handlerList[eventId] = newHandler;
+}
+
+void MFInputShifter::detach()
+{
+  if (!_initialized)
+    return;
+  _initialized = false;
+}
+
+// Clears the internal state of the shifter, including all received bits
+// and the timestamp for the last time the data was read.
+void MFInputShifter::clear()
+{
+  _last = 0;
+  clearLastState();
+}
+
+// Sets the last recorded state of every bit on every shifter to 0.
+void MFInputShifter::clearLastState()
+{
+  for (int i = 0; i < MAX_CHAINED_INPUT_SHIFTERS; i++)
+  {
+    _lastState[i] = 0;
+  }
+}