Merge branch 'develop' into fix/ble-battery-level-bas

Address review feedback on the Battery Level characteristic (0x2A19):

- Clamp the value to the BAS-mandated 0-100 range at the platform write
  boundary (NimBLE seed + update, NRF52 update), so a misbehaving battery
  backend can't put an out-of-range value on the characteristic.
- Skip the write/notify when the level is unchanged, so repeated callers
  (e.g. MeshService refresh paths) don't emit redundant notifications.
- Simplify Power.cpp to a direct guarded call now that clamping and
  de-duplication live at the boundary, which also removes the implicit
  int->uint8_t narrowing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/Power.cpp

@@ -14,6 +14,7 @@
  * For more information, see: https://meshtastic.org/
  */
 #include "power.h"
+#include "BluetoothCommon.h"
 #include "MessageStore.h"
 #include "NodeDB.h"
 #include "PowerFSM.h"
@@ -962,6 +963,10 @@ void Power::readPowerStatus()
         lastLogTime = millis();
     }
     newStatus.notifyObservers(&powerStatus2);
+
+    // Mirror battery level to the BLE Battery Service (0x2A19); the platform layer clamps and dedupes.
+    if (hasBattery == OptTrue)
+        updateBatteryLevel(powerStatus2.getBatteryChargePercent());
 #ifdef DEBUG_HEAP
     if (lastheap != memGet.getFreeHeap()) {
         // Use stack-allocated buffer to avoid heap allocations in monitoring code

src/nimble/NimbleBluetooth.cpp

@@ -40,6 +40,7 @@ constexpr uint16_t kPreferredBleTxTimeUs = (kPreferredBleTxOctets + 14) * 8;
 
 BLECharacteristic *fromNumCharacteristic;
 BLECharacteristic *BatteryCharacteristic;
+static int lastBatteryLevel = -1; // last value written to 0x2A19, to skip redundant writes/notifies
 BLECharacteristic *logRadioCharacteristic;
 BLEServer *bleServer;
 
@@ -718,6 +719,8 @@ void NimbleBluetooth::deinit()
 #endif
 
     BLEDevice::deinit(true);
+    BatteryCharacteristic = nullptr; // freed by deinit; clear so updateBatteryLevel() won't touch it
+    lastBatteryLevel = -1;
 #endif
 }
 
@@ -856,16 +859,31 @@ void NimbleBluetooth::setupService()
     BatteryCharacteristic = batteryService->createCharacteristic( // 0x2A19 is the Battery Level characteristic)
         (uint16_t)0x2a19, BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_NOTIFY);
     BatteryCharacteristic->addDescriptor(batteryLevelDescriptor);
+    // Seed an initial 0-100 level so an early read of 0x2A19 returns a valid value.
+    uint8_t initialLevel = (powerStatus && powerStatus->getHasBattery()) ? powerStatus->getBatteryChargePercent() : 0;
+    if (initialLevel > 100)
+        initialLevel = 100;
+    BatteryCharacteristic->setValue(&initialLevel, 1);
+    lastBatteryLevel = initialLevel;
     batteryService->start();
 }
 
 /// Given a level between 0-100, update the BLE attribute
 void updateBatteryLevel(uint8_t level)
 {
-    if ((config.bluetooth.enabled == true) && nimbleBluetooth && nimbleBluetooth->isConnected()) {
-        BatteryCharacteristic->setValue(&level, 1);
+    if (!config.bluetooth.enabled || !BatteryCharacteristic)
+        return;
+
+    if (level > 100) // 0x2A19 must stay within the BAS 0-100 range
+        level = 100;
+    if (level == lastBatteryLevel)
+        return;
+    lastBatteryLevel = level;
+
+    // Cache the value so a READ works without a subscriber; notify only when connected.
+    BatteryCharacteristic->setValue(&level, 1);
+    if (nimbleBluetooth && nimbleBluetooth->isConnected())
         BatteryCharacteristic->notify();
-    }
 }
 
 void NimbleBluetooth::clearBonds()

src/platform/nrf52/NRF52Bluetooth.cpp

@@ -15,8 +15,9 @@ static BLECharacteristic fromRadio = BLECharacteristic(BLEUuid(FROMRADIO_UUID_16
 static BLECharacteristic toRadio = BLECharacteristic(BLEUuid(TORADIO_UUID_16));
 static BLECharacteristic logRadio = BLECharacteristic(BLEUuid(LOGRADIO_UUID_16));
 
-static BLEDis bledis; // DIS (Device Information Service) helper class instance
-static BLEBas blebas; // BAS (Battery Service) helper class instance
+static BLEDis bledis;             // DIS (Device Information Service) helper class instance
+static BLEBas blebas;             // BAS (Battery Service) helper class instance
+static int lastBatteryLevel = -1; // last value written to BAS, to skip redundant writes/notifies
 #ifndef BLE_DFU_SECURE
 static BLEDfu bledfu; // DFU software update helper service
 #else
@@ -336,6 +337,7 @@ void NRF52Bluetooth::setup()
     LOG_INFO("Init the Battery Service");
     blebas.begin();
     blebas.write(0); // Unknown battery level for now
+    lastBatteryLevel = 0;
     // Setup the Heart Rate Monitor service using
     // BLEService and BLECharacteristic classes
     LOG_INFO("Init the Mesh bluetooth service");
@@ -355,6 +357,14 @@ void NRF52Bluetooth::resumeAdvertising()
 /// Given a level between 0-100, update the BLE attribute
 void updateBatteryLevel(uint8_t level)
 {
+    if (!nrf52Bluetooth) // skip until the Battery Service has been begun in setup()
+        return;
+
+    if (level > 100) // BAS battery level must stay within 0-100
+        level = 100;
+    if (level == lastBatteryLevel)
+        return;
+    lastBatteryLevel = level;
     blebas.write(level);
 }
 void NRF52Bluetooth::clearBonds()