Use Converter methods to convert bytes Medisana

android_app/app/src/main/java/com/health/openscale/core/bluetooth/BluetoothMedisanaBS444.java

@@ -20,6 +20,7 @@ import android.bluetooth.BluetoothGattCharacteristic;
 import android.content.Context;
 
 import com.health.openscale.core.datatypes.ScaleMeasurement;
+import com.health.openscale.core.utils.Converters;
 
 import java.util.Date;
 import java.util.UUID;
@@ -35,6 +36,9 @@ public class BluetoothMedisanaBS444 extends BluetoothCommunication {
 
     private ScaleMeasurement btScaleMeasurement;
 
+    // Scale time is in seconds since 2010-01-01
+    private static final long SCALE_UNIX_TIMESTAMP_OFFSET = 1262304000;
+
     public BluetoothMedisanaBS444(Context context) {
         super(context);
         btScaleMeasurement = new ScaleMeasurement();
@@ -67,17 +71,11 @@ public class BluetoothMedisanaBS444 extends BluetoothCommunication {
                 break;
             case 3:
                 // send magic number to receive weight data
-                Date date = new Date();
+                long timestamp = new Date().getTime() / 1000;
-                int unix_timestamp = (int) ((date.getTime() / 1000) - 1262304000); // -40 years because unix time starts in year 1970
+                timestamp -= SCALE_UNIX_TIMESTAMP_OFFSET;
+                byte[] date = Converters.toUnsignedInt32Le(timestamp);
 
-                byte[] magicBytes = new byte[] {
+                byte[] magicBytes = new byte[] {(byte)0x02, date[0], date[1], date[2], date[3]};
-                        (byte)0x02,
-                        (byte)(unix_timestamp),
-                        (byte)(unix_timestamp >>> 8),
-                        (byte)(unix_timestamp >>> 16),
-                        (byte)(unix_timestamp >>> 24)
-                };
-                //byte[] magicBytes = new byte[]{(byte)0x02, (byte)0x7B, (byte)0x7B, (byte)0xF6, (byte)0x0D}; // 02:7b:7b:f6:0d
 
                 writeBytes(WEIGHT_MEASUREMENT_SERVICE, CMD_MEASUREMENT_CHARACTERISTIC, magicBytes);
                 break;
@@ -110,26 +108,23 @@ public class BluetoothMedisanaBS444 extends BluetoothCommunication {
     }
 
     private void parseWeightData(byte[] weightData) {
-        float weight = (float)(((weightData[2] & 0xFF) << 8) | (weightData[1] & 0xFF)) / 100.0f;
+        float weight = Converters.fromUnsignedInt16Le(weightData, 1) / 100.0f;
-        long unix_timestamp = ((weightData[8] & 0xFF) << 24) | ((weightData[7] & 0xFF) << 16) | ((weightData[6] & 0xFF) << 8) | (weightData[5] & 0xFF); // elapsed time in seconds since 2010
+        long timestamp = Converters.fromUnsignedInt32Le(weightData, 5);
+        timestamp += SCALE_UNIX_TIMESTAMP_OFFSET;
 
-        Date btDate = new Date();
+        btScaleMeasurement.setDateTime(new Date(timestamp * 1000));
-        unix_timestamp += 1262304000; // +40 years because unix time starts in year 1970
-        btDate.setTime(unix_timestamp*1000); // multiply with 1000 to get milliseconds
-
-        btScaleMeasurement.setDateTime(btDate);
         btScaleMeasurement.setWeight(weight);
     }
 
     private void parseFeatureData(byte[] featureData) {
-        //btScaleData.setKCal(((featureData[7] & 0xFF) << 8) | (featureData[6] & 0xFF));
+        //btScaleData.setKCal(Converters.fromUnsignedInt16Le(featureData, 6));
-        btScaleMeasurement.setFat(decodeFeature(featureData[8], featureData[9]));
+        btScaleMeasurement.setFat(decodeFeature(featureData, 8));
-        btScaleMeasurement.setWater(decodeFeature(featureData[10], featureData[11]));
+        btScaleMeasurement.setWater(decodeFeature(featureData, 10));
-        btScaleMeasurement.setMuscle(decodeFeature(featureData[12], featureData[13]));
+        btScaleMeasurement.setMuscle(decodeFeature(featureData, 12));
-        btScaleMeasurement.setBone(decodeFeature(featureData[14], featureData[15]));
+        btScaleMeasurement.setBone(decodeFeature(featureData, 14));
     }
 
-    private float decodeFeature(byte highByte, byte lowByte) {
+    private float decodeFeature(byte[] featureData, int offset) {
-        return (float)(((lowByte& 0x0F) << 8) | (highByte & 0xFF)) / 10.0f;
+        return (Converters.fromUnsignedInt16Le(featureData, offset) & 0x0FFF) / 10.0f;
     }
 }

android_app/app/src/main/java/com/health/openscale/core/utils/Converters.java

@@ -150,6 +150,14 @@ public class Converters {
         return value;
     }
 
+    public static long fromUnsignedInt32Le(byte[] data, int offset) {
+        long value = (long) (data[offset + 3] & 0xFF) << 24;
+        value += (data[offset + 2] & 0xFF) << 16;
+        value += (data[offset + 1] & 0xFF) << 8;
+        value += data[offset] & 0xFF;
+        return value;
+    }
+
     public static long fromUnsignedInt32Be(byte[] data, int offset) {
         long value = (long) (data[offset] & 0xFF) << 24;
         value += (data[offset + 1] & 0xFF) << 16;
@@ -158,6 +166,15 @@ public class Converters {
         return value;
     }
 
+    public static byte[] toUnsignedInt32Le(long value) {
+        byte[] data = new byte[4];
+        data[3] = (byte) ((value >> 24) & 0xFF);
+        data[2] = (byte) ((value >> 16) & 0xFF);
+        data[1] = (byte) ((value >> 8) & 0xFF);
+        data[0] = (byte) (value & 0xFF);
+        return data;
+    }
+
     public static byte[] toUnsignedInt32Be(long value) {
         byte[] data = new byte[4];
         data[0] = (byte) ((value >> 24) & 0xFF);

android_app/app/src/test/java/com/health/openscale/ConvertersTest.java

@@ -114,15 +114,27 @@ public class ConvertersTest {
     @Test
     public void unsignedInt32Converters() throws Exception {
         byte[] data = new byte[]{(byte) 0xf1, (byte) 0xf2, (byte) 0xf3, (byte) 0x7f, (byte) 0x7e};
+
+        assertEquals(0x7ff3f2f1, Converters.fromUnsignedInt32Le(data, 0));
+        assertEquals(0x7e7ff3f2, Converters.fromUnsignedInt32Le(data, 1));
+
         assertEquals(0xf1f2f37fL, Converters.fromUnsignedInt32Be(data, 0));
         assertEquals(0xf2f37f7eL, Converters.fromUnsignedInt32Be(data, 1));
 
         data = new byte[]{(byte) 0x80, (byte) 0x00, (byte) 0x01, (byte) 0xff, (byte) 0x00};
+
+        assertEquals(0xff010080L, Converters.fromUnsignedInt32Le(data, 0));
+        assertEquals(0xff0100, Converters.fromUnsignedInt32Le(data, 1));
+
         assertEquals(0x800001ffL, Converters.fromUnsignedInt32Be(data, 0));
         assertEquals(0x1ff00L, Converters.fromUnsignedInt32Be(data, 1));
 
         data = new byte[]{(byte) 0xff, (byte) 0xfe, (byte) 0xfd, (byte) 0xfc};
+        assertArrayEquals(data, Converters.toUnsignedInt32Le(0xfcfdfeffL));
         assertArrayEquals(data, Converters.toUnsignedInt32Be(0xfffefdfcL));
+        assertEquals(0xffffffffL,
+                Converters.fromUnsignedInt32Le(
+                        Converters.toUnsignedInt32Le(0xffffffffL), 0));
         assertEquals(0xffffffffL,
                 Converters.fromUnsignedInt32Be(
                         Converters.toUnsignedInt32Be(0xffffffffL), 0));