fix BLE control characteristic UUID regression (#1208)

The BLE write characteristic UUID was mistakenly changed from the
correct value (…2b11) to the service UUID (…1910) during the
refactoring in 14f3bd8, causing "Control characteristic not found"
errors on BLE-only devices like the H617A.

Also adds debug logging of discovered characteristic UUIDs when
the control characteristic is not found, to aid future diagnosis.

Author: duggan

lib/connection/ble.js

@@ -33,7 +33,7 @@ process.on('unhandledRejection', (reason) => {
 
 const H5075_UUID = 'ec88'
 const H5101_UUID = '0001'
-const CONTROL_CHARACTERISTIC_UUID = '000102030405060708090a0b0c0d1910'
+const CONTROL_CHARACTERISTIC_UUID = '000102030405060708090a0b0c0d2b11'
 const CONNECTION_TIMEOUT = 10000 // 10 seconds
 const WRITE_TIMEOUT = 5000 // 5 seconds
 
@@ -237,6 +237,8 @@ export default class BLEConnection {
       )
 
       if (!characteristic) {
+        const discoveredUuids = Object.values(characteristics).map(c => c.uuid)
+        accessory.logDebug(`discovered characteristics: ${JSON.stringify(discoveredUuids)}`)
         throw new Error('Control characteristic not found')
       }
       accessory.logDebug('found control characteristic')