Initial physical button mapping implementation #4

source/config.h

@@ -10,6 +10,7 @@
 #define FEATURE_AUTO_RECAL
 #define FEATURE_BATTERY_MONITOR
 #define FEATURE_BOOT_LOOP_DETECT
+#define FEATURE_PHYSICAL_BUTTONS
 
 // ─── Debug ────────────────────────────────────────────────────────────────────
 // #define DEBUG
@@ -53,7 +54,10 @@
 
 // ─── Persistence ──────────────────────────────────────────────────────────────
 #define CONFIG_FILENAME  "/imu_mouse_cfg.bin"
-#define CONFIG_MAGIC     0xDEAD123CUL
+#define CONFIG_MAGIC     0xDEAD123DUL
+
+// ─── Physical button sentinel ─────────────────────────────────────────────────
+#define BTN_PIN_NONE  0xFF   // Stored in btn*Pin when that button is disabled
 
 // ─── Runtime feature-override flags (cfg.featureFlags bitmask) ───────────────
 // These mirror the compile-time FEATURE_* defines but can be toggled at runtime
@@ -94,6 +98,9 @@ struct Config {
   float      jerkThreshold;    // jerk² threshold for tap-freeze detection
   uint8_t    tapFreezeEnabled; // 1 = enable jerk-based cursor freeze during taps
   uint8_t    featureFlags;     // bitmask of FLAG_* — runtime feature overrides
+  uint8_t    btnLeftPin;       // BTN_PIN_NONE or Arduino pin number (0-10 = D0-D10)
+  uint8_t    btnRightPin;
+  uint8_t    btnMiddlePin;
 };
 extern Config cfg;
 extern const Config CFG_DEFAULTS;
@@ -113,8 +120,11 @@ struct __attribute__((packed)) ConfigBlob {
   uint8_t tapFreezeEnabled;  // [19]  1 = enable jerk-based cursor freeze during taps
   float   jerkThreshold;     // [20]  jerk² tap-freeze threshold
   uint8_t featureFlags;      // [24]  FLAG_* bitmask — runtime feature overrides
+  uint8_t btnLeftPin;        // [25]  BTN_PIN_NONE or Arduino pin (0-10 = D0-D10)
+  uint8_t btnRightPin;       // [26]
+  uint8_t btnMiddlePin;      // [27]
 };
-static_assert(sizeof(ConfigBlob) == 25, "ConfigBlob must be 25 bytes");
+static_assert(sizeof(ConfigBlob) == 28, "ConfigBlob must be 28 bytes");
 
 // ─── TelemetryPacket (24 bytes) ───────────────────────────────────────────────
 #ifdef FEATURE_TELEMETRY