migrate Gravity firmware into a new dedicated firmware directory.

firmware/Gravity/save_state.h

@@ -0,0 +1,83 @@
+#ifndef SAVE_STATE_H
+#define SAVE_STATE_H
+
+#include <Arduino.h>
+#include <gravity.h>
+
+// Forward-declare AppState to avoid circular dependencies.
+struct AppState;
+
+// Define the constants for the current firmware.
+const char SKETCH_NAME[] = "Gravity";
+const byte SKETCH_VERSION = 7;
+
+// Number of available save slots.
+const byte MAX_SAVE_SLOTS = 10;
+
+// Define the minimum amount of time between EEPROM writes.
+static const unsigned long SAVE_DELAY_MS = 2000;
+
+/**
+ * @brief Manages saving and loading of the application state to and from EEPROM.
+ * The number of user slots is defined by MAX_SAVE_SLOTS, and one additional slot
+ * is reseved for transient state to persist state between power cycles before
+ * state is explicitly saved to a user slot. Metadata is stored in the beginning
+ * of the memory space which stores firmware version information to validate that
+ * the data can be loaded into the current version of AppState.
+ */
+class StateManager {
+   public:
+    StateManager();
+
+    // Populate the AppState instance with values from EEPROM if they exist.
+    bool initialize(AppState& app);
+    // Load data from specified slot.
+    bool loadData(AppState& app, byte slot_index);
+    // Save data to specified slot.
+    void saveData(const AppState& app);
+    // Reset AppState instance back to default values.
+    void reset(AppState& app);
+    // Call from main loop, check if state has changed and needs to be saved.
+    void update(const AppState& app);
+    // Indicate that state has changed and we should save.
+    void markDirty();
+
+    // This struct holds the data that identifies the firmware version.
+    struct Metadata {
+        byte version;
+        char sketch_name[16];
+    };
+    struct ChannelState {
+        byte base_clock_mod_index;
+        byte base_probability;
+        byte base_duty_cycle;
+        byte base_offset;
+        byte base_swing;
+        byte base_euc_steps;
+        byte base_euc_hits;
+        byte cv1_dest;  // Cast the CvDestination enum as a byte for storage
+        byte cv2_dest;  // Cast the CvDestination enum as a byte for storage
+    };
+    // This struct holds all the parameters we want to save.
+    struct EepromData {
+        int tempo;
+        bool encoder_reversed;
+        byte selected_param;
+        byte selected_channel;
+        byte selected_source;
+        byte selected_pulse;
+        byte selected_save_slot;
+        ChannelState channel_data[Gravity::OUTPUT_COUNT];
+    };
+
+   private:
+    bool _isDataValid();
+    void _saveMetadata();
+    void _saveState(const AppState& app, byte slot_index);
+    void _loadState(AppState& app, byte slot_index);
+
+    bool _isDirty;
+    unsigned long _lastChangeTime;
+};
+
+#endif  // SAVE_STATE_H