Add missing buttons.h

src/modules/buttons.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <stdint.h>
 #include "../hal/adc.h"
 
 /// Buttons are built on top of the raw ADC API
@@ -8,16 +9,38 @@
 namespace modules {
 
 struct Button {
+    inline constexpr Button()
+        : state(State::Waiting)
+        , tmp(false)
+        , pressed(false)
+        , timeLastChange(0) {}
+
     /// @returns true if button is currently considered as pressed
-    bool Pressed() const;
+    inline bool Pressed() const { return pressed; }
+
+    /// State machine stepping routine
+    void Step(uint16_t time, bool press);
 
 private:
-    uint8_t lastState;
-    uint16_t timeElapsedLastChange;
+    constexpr static const uint16_t debounce = 100; ///< time interval for debouncing @@TODO specify units
+    enum class State : uint_fast8_t { Waiting = 0,
+        Detected,
+        WaitForRelease,
+        Update };
+    State state;
+    bool tmp; ///< temporary state of button before the debouncing state machine finishes
+    bool pressed; ///< real state of button after debouncing
+    uint16_t timeLastChange;
 };
 
 class Buttons {
+    constexpr static const uint8_t N = 3; ///< number of buttons currently supported
+    constexpr static const uint8_t adc = 1; ///< ADC index - will be some define or other constant later on
+    static uint16_t tmpTiming;
+
 public:
+    inline constexpr Buttons() = default;
+
     /// State machine step - reads the ADC, processes debouncing, updates states of individual buttons
     void Step();
 
@@ -26,7 +49,8 @@ public:
     inline bool ButtonPressed(uint8_t index) const { return buttons[index].Pressed(); }
 
 private:
-    Button buttons[3]; ///< @@TODO parametrize/generalize?
+    Button buttons[N];
+    static int8_t Sample();
 };
 
 } // namespace modules