Fix Initial Transient State (#17)

There was an off-by-one error that was not properly loading transient state from the designated memory slot. Also fixes setting the last saved/loaded slot indicator with metadata.

Reviewed-on: https://git.pinkduck.xyz/awonak/libGravity/pulls/17

firmware/Gravity/save_state.cpp

@@ -24,7 +24,7 @@ StateManager::StateManager() : _isDirty(false), _lastChangeTime(0) {}
 bool StateManager::initialize(AppState& app) {
     if (_isDataValid()) {
         // Load data from the transient slot.
-        return loadData(app, MAX_SAVE_SLOTS);
+        return loadData(app, TRANSIENT_SLOT);
     }
     // EEPROM does not contain save data for this firmware & version.
     else {
@@ -33,17 +33,17 @@ bool StateManager::initialize(AppState& app) {
         // Initialize eeprom and save default patter to all save slots.
         _saveMetadata(app);
         reset(app);
-        // MAX_SAVE_SLOTS slot is reserved for transient state.
+        for (int i = 0; i < MAX_SAVE_SLOTS; i++) {
-        for (int i = 0; i <= MAX_SAVE_SLOTS; i++) {
-            app.selected_save_slot = i;
             _saveState(app, i);
         }
+        _saveState(app, TRANSIENT_SLOT);
         return false;
     }
 }
 
 bool StateManager::loadData(AppState& app, byte slot_index) {
-    if (slot_index >= MAX_SAVE_SLOTS) return false;
+    // Check if slot_index is within max range + 1 for transient.
+    if (slot_index >= MAX_SAVE_SLOTS + 1) return false;
 
     _loadState(app, slot_index);
     _loadMetadata(app);
@@ -53,7 +53,8 @@ bool StateManager::loadData(AppState& app, byte slot_index) {
 
 // Save app state to user specified save slot.
 void StateManager::saveData(const AppState& app) {
-    if (app.selected_save_slot >= MAX_SAVE_SLOTS) return;
+    // Check if slot_index is within max range + 1 for transient.
+    if (app.selected_save_slot >= MAX_SAVE_SLOTS + 1) return;
 
     _saveState(app, app.selected_save_slot);
     _isDirty = false;
@@ -62,8 +63,7 @@ void StateManager::saveData(const AppState& app) {
 // Save transient state if it has changed and enough time has passed since last save.
 void StateManager::update(const AppState& app) {
     if (_isDirty && (millis() - _lastChangeTime > SAVE_DELAY_MS)) {
-        // MAX_SAVE_SLOTS slot is reserved for transient state.
+        _saveState(app, TRANSIENT_SLOT);
-        _saveState(app, MAX_SAVE_SLOTS);
         _saveMetadata(app);
         _isDirty = false;
     }
@@ -110,7 +110,8 @@ bool StateManager::_isDataValid() {
 }
 
 void StateManager::_saveState(const AppState& app, byte slot_index) {
-    if (app.selected_save_slot >= MAX_SAVE_SLOTS) return;
+    // Check if slot_index is within max range + 1 for transient.
+    if (app.selected_save_slot >= MAX_SAVE_SLOTS + 1) return;
 
     noInterrupts();
     static EepromData save_data;
@@ -121,7 +122,6 @@ void StateManager::_saveState(const AppState& app, byte slot_index) {
     save_data.selected_channel = app.selected_channel;
     save_data.selected_source = static_cast<byte>(app.selected_source);
     save_data.selected_pulse = static_cast<byte>(app.selected_pulse);
-    save_data.selected_save_slot = app.selected_save_slot;
 
     // TODO: break this out into a separate function. Save State should be
     // broken out into global / per-channel save methods. When saving via
@@ -147,6 +147,9 @@ void StateManager::_saveState(const AppState& app, byte slot_index) {
 }
 
 void StateManager::_loadState(AppState& app, byte slot_index) {
+    // Check if slot_index is within max range + 1 for transient.
+    if (slot_index >= MAX_SAVE_SLOTS + 1) return;
+
     noInterrupts();
     static EepromData load_data;
     int address = EEPROM_DATA_START_ADDR + (slot_index * sizeof(EepromData));
@@ -184,6 +187,7 @@ void StateManager::_saveMetadata(const AppState& app) {
     current_meta.version = SKETCH_VERSION;
 
     // Global user settings
+    current_meta.selected_save_slot = app.selected_save_slot;
     current_meta.encoder_reversed = app.encoder_reversed;
 
     EEPROM.put(METADATA_START_ADDR, current_meta);
@@ -194,6 +198,7 @@ void StateManager::_loadMetadata(AppState& app) {
     noInterrupts();
     Metadata metadata;
     EEPROM.get(METADATA_START_ADDR, metadata);
+    app.selected_save_slot = metadata.selected_save_slot;
     app.encoder_reversed = metadata.encoder_reversed;
     interrupts();
 }

firmware/Gravity/save_state.h

@@ -23,7 +23,8 @@ const char SKETCH_NAME[] = "AltGravity";
 const byte SKETCH_VERSION = 1;
 
 // Number of available save slots.
-const byte MAX_SAVE_SLOTS = 10;
+const byte MAX_SAVE_SLOTS = 10;  // Count of save slots 0 - 9 to save/load  presets.
+const byte TRANSIENT_SLOT = 10;  // Transient slot index to persist state when powered off.
 
 // Define the minimum amount of time between EEPROM writes.
 static const unsigned long SAVE_DELAY_MS = 2000;
@@ -60,6 +61,7 @@ class StateManager {
         byte version;
         char sketch_name[16];
         // Additional global/hardware settings
+        byte selected_save_slot;
         bool encoder_reversed;
     };
     struct ChannelState {
@@ -81,7 +83,6 @@ class StateManager {
         byte selected_channel;
         byte selected_source;
         byte selected_pulse;
-        byte selected_save_slot;
         ChannelState channel_data[Gravity::OUTPUT_COUNT];
     };