Use period characteristic to set accelerometer period (#36)

Author: microbit-robert

lib/accelerometer-service.ts

@@ -100,7 +100,9 @@ export class AccelerometerService implements Service {
     const dataView = new DataView(new ArrayBuffer(2));
     dataView.setUint16(0, value, true);
     return this.queueGattOperation(() =>
-      this.accelerometerDataCharacteristic.writeValueWithoutResponse(dataView),
+      this.accelerometerPeriodCharacteristic.writeValueWithoutResponse(
+        dataView,
+      ),
     );
   }