Add skeleton app to examples

examples/skeleton/skeleton.ino

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+/**
+ * @file skeleton.ino
+ * @author YOUR_NAME (<url>)
+ * @brief Skeleton app for Sitka Instruments Gravity.
+ * @version v1.0.0 - August 2025
+ * @date 2025-08-12
+ *
+ * @copyright MIT - (c) 2025 - Adam Wonak - adam.wonak@gmail.com
+ * 
+ * Skeleton app for basic structure of a new firmware for Sitka Instruments
+ * Gravity using the libGravity library.
+ *
+ * ENCODER:
+ *      Press: change between selecting a parameter and editing the parameter.
+ *      Hold & Rotate: change current selected output channel.
+ *
+ * BTN1:
+ *      Play/pause - start or stop the internal clock.
+ *
+ * BTN2:
+ *      Shift - hold and rotate encoder to change current selected output channel.
+ *
+ * EXT:
+ *      External clock input. When Gravity is set to INTERNAL or MIDI clock
+ *      source, this input is used to reset clocks.
+ *
+ * CV1:
+ *      External analog input used to provide modulation to any channel parameter.
+ *
+ * CV2:
+ *      External analog input used to provide modulation to any channel parameter.
+ *
+ */
+
+#include <libGravity.h>
+
+
+
+// Global state for settings and app behavior.
+struct AppState {
+    int tempo = Clock::DEFAULT_TEMPO;
+    Clock::Source selected_source = Clock::SOURCE_INTERNAL;
+    // Add app specific state variables here.
+};
+
+AppState app;
+
+//
+// Arduino setup and loop.
+//
+
+void setup() {
+    // Start Gravity.
+    gravity.Init();
+
+    // Clock handlers.
+    gravity.clock.AttachIntHandler(HandleIntClockTick);
+    gravity.clock.AttachExtHandler(HandleExtClockTick);
+
+    // Encoder rotate and press handlers.
+    gravity.encoder.AttachPressHandler(HandleEncoderPressed);
+    gravity.encoder.AttachRotateHandler(HandleRotate);
+    gravity.encoder.AttachPressRotateHandler(HandlePressedRotate);
+
+    // Button press handlers.
+    gravity.play_button.AttachPressHandler(HandlePlayPressed);
+}
+
+void loop() {
+    // Process change in state of inputs and outputs.
+    gravity.Process();
+
+    // Non-ISR loop behavior.
+}
+
+//
+// Firmware handlers for clocks.
+//
+
+void HandleIntClockTick(uint32_t tick) {
+    bool refresh = false;
+    for (int i = 0; i < Gravity::OUTPUT_COUNT; i++) {
+        // Process each output tick handlers.
+    }
+}
+
+void HandleExtClockTick() {
+    switch (app.selected_source) {
+        case Clock::SOURCE_INTERNAL:
+        case Clock::SOURCE_EXTERNAL_MIDI:
+            // Use EXT as Reset when not used for clock source.
+            gravity.clock.Reset();
+            break;
+        default:
+            // Register EXT cv clock tick.
+            gravity.clock.Tick();
+    }
+}
+
+//
+// UI handlers for encoder and buttons.
+//
+
+void HandlePlayPressed() {
+}
+
+void HandleEncoderPressed() {
+}
+
+void HandleRotate(int val) {
+}
+
+void HandlePressedRotate(int val) {
+}
+
+//
+// Application logic goes here.
+//