Merge with a128c27963002c1d46170696e1c1045db4e1de87

MyTracks/src/com/google/android/apps/mytracks/services/sensors/SensorUtils.java

@@ -24,14 +24,16 @@ import com.google.android.maps.mytracks.R;
  * A collection of methods for message parsers.
  *
  * @author Sandor Dornbush
+ * @author Nico Laum
  */
 public class SensorUtils {
 
   private SensorUtils() {
   }
-
+  
   /**
    * Extract one unsigned short from a big endian byte array.
+   * 
    * @param buffer the buffer to extract the short from
    * @param index the first byte to be interpreted as part of the short
    * @return The unsigned short at the given index in the buffer
@@ -42,6 +44,58 @@ public class SensorUtils {
     return r;
   }
 
+  /**
+   * Extract one unsigned short from a little endian byte array.
+   * 
+   * @param buffer the buffer to extract the short from
+   * @param index the first byte to be interpreted as part of the short
+   * @return The unsigned short at the given index in the buffer
+   */
+  public static int unsignedShortToIntLittleEndian(byte[] buffer, int index) {
+    int r = buffer[index] & 0xFF;
+    r |= (buffer[index + 1] & 0xFF) << 8;
+    return r;
+  }
+
+  /**
+   * Returns CRC8 (polynomial 0x8C) from byte array buffer[start] until
+   * (including) buffer[end]
+   * 
+   * @param buffer the byte array of data (payload)
+   * @param start the position in the byte array where the payload begins
+   * @param end the position in the byte array where the payload ends
+   * @return CRC8 value
+   */
+  public static byte getCrc8(byte[] buffer, int start, int length) {
+    byte crc = 0x0;
+
+    for (int i = start; i < (start + length); i++) {
+      crc = crc8PushByte(crc, buffer[i]);
+    }
+    return crc;
+  }
+
+  /**
+   * Updates a CRC8 value by using the next byte passed to this method
+   * 
+   * @param crc int of crc value
+   * @param add the next byte to add to the CRC8 calculation
+   */
+  private static byte crc8PushByte(byte crc, byte add) {
+    crc = (byte) (crc ^ add);
+    
+    for (int i = 0; i < 8; i++) {
+      if ((crc & 0x1) != 0x0) {
+	// Using a 0xFF bit assures that 0-bits are introduced during the shift operation. 
+	// Otherwise, implicit casts to signed int could shift in 1-bits if the signed bit is 1.
+        crc = (byte) (((crc & 0xFF) >> 1) ^ 0x8C);
+      } else {
+        crc = (byte) ((crc & 0xFF) >> 1);
+      }
+    }
+    return crc;
+  }
+	
   public static String getStateAsString(Sensor.SensorState state, Context c) {
     switch (state) {
       case NONE:

MyTracks/src/com/google/android/apps/mytracks/services/sensors/ZephyrMessageParser.java

@@ -21,12 +21,16 @@ import com.google.android.apps.mytracks.Constants;
 import com.google.android.apps.mytracks.content.Sensor;
 
 /**
- * An implementation of a SensorData parser for Zephyr HRM.
+ * An implementation of a Sensor MessageParser for Zephyr.
  *
  * @author Sandor Dornbush
  */
 public class ZephyrMessageParser implements MessageParser {
 
+  public static final int ZEPHYR_HXM_BYTE_STX = 0;
+  public static final int ZEPHYR_HXM_BYTE_CRC = 58;
+  public static final int ZEPHYR_HXM_BYTE_ETX = 59;
+	
   @Override
   public Sensor.SensorDataSet parseBuffer(byte[] buffer) {
     StringBuilder sb = new StringBuilder();
@@ -34,20 +38,24 @@ public class ZephyrMessageParser implements MessageParser {
       sb.append(String.format("%02X", buffer[i]));
     }
     Log.w(Constants.TAG, "Got zephyr data: " + sb);
-    // The provided units are 1/16 strides per minute.
-    // TODO: Fix the cadence calculation.
-    // int cadence = SensorUtils.unsignedShortToInt(buffer, 56);
     // Heart Rate
-    Sensor.SensorData.Builder b = Sensor.SensorData.newBuilder()
-      .setValue(buffer[12] & 0xFF)
-      .setState(Sensor.SensorState.SENDING);
-      // Cadence
-      //.setCadence(cadence / 16)
-      //.build();
+    Sensor.SensorData.Builder heartrate = Sensor.SensorData.newBuilder()
+        .setValue(buffer[12])
+        .setState(Sensor.SensorState.SENDING);
+    // Changes Nico Laum (Power and Cadence)
+    Sensor.SensorData.Builder power = Sensor.SensorData.newBuilder()
+	    .setValue(buffer[11])
+	    .setState(Sensor.SensorState.SENDING);
+    Sensor.SensorData.Builder cadence = Sensor.SensorData.newBuilder()
+	    .setValue(SensorUtils.unsignedShortToIntLittleEndian(buffer, 56) / 16)
+	    .setState(Sensor.SensorState.SENDING);
+    
     Sensor.SensorDataSet sds =
       Sensor.SensorDataSet.newBuilder()
       .setCreationTime(System.currentTimeMillis())
-      .setHeartRate(b)
+      .setPower(power)
+      .setHeartRate(heartrate)
+      .setCadence(cadence)
       .build();
     
     return sds;
@@ -55,8 +63,11 @@ public class ZephyrMessageParser implements MessageParser {
 
   @Override
   public boolean isValid(byte[] buffer) {
-    // TODO crc etc.
-    return buffer[0] == 0x02 && buffer[59] == 0x03;
+    // Check STX (Start of Text), ETX (End of Text) and CRC Checksum
+    return buffer.length > ZEPHYR_HXM_BYTE_ETX
+        && buffer[ZEPHYR_HXM_BYTE_STX] == 0x02
+        && buffer[ZEPHYR_HXM_BYTE_ETX] == 0x03
+        && SensorUtils.getCrc8(buffer, 3, 55) == buffer[ZEPHYR_HXM_BYTE_CRC];
   }
 
   @Override

MyTracksTest/src/com/google/android/apps/mytracks/services/sensors/ZephyrMessageParserTest.java

@@ -9,10 +9,17 @@ public class ZephyrMessageParserTest extends TestCase {
   ZephyrMessageParser parser = new ZephyrMessageParser();
 
   public void testIsValid() {
-    byte[] buf = new byte[60];
+    byte[] smallBuf = new byte[59];
+    assertFalse(parser.isValid(smallBuf));
+    // A complete and valid Zephyr HxM packet
+    byte[] buf = { 2,38,55,26,0,49,101,80,0,49,98,100,42,113,120,-53,-24,-60,-123,-61,117,-69,42,-75,74,-78,51,-79,27,-83,28,-88,28,-93,29,-98,25,-103,26,-108,26,-113,59,-118,0,0,0,0,0,0,-22,3,125,1,48,0,96,4,30,0 };
+    // Make buffer invalid
+    buf[0] = buf[58] = buf[59] = 0;
     assertFalse(parser.isValid(buf));
     buf[0] = 0x02;
     assertFalse(parser.isValid(buf));
+    buf[58] = 0x1E;
+    assertFalse(parser.isValid(buf));
     buf[59] = 0x03;
     assertTrue(parser.isValid(buf));
   }
@@ -20,10 +27,19 @@ public class ZephyrMessageParserTest extends TestCase {
   public void testParseBuffer() {
     byte[] buf = new byte[60];
     buf[12] = 50;
+    buf[11] = 51;
+    buf[56] = 32;
+    buf[57] = 0;
     Sensor.SensorDataSet sds = parser.parseBuffer(buf);
     assertTrue(sds.hasHeartRate());
     assertTrue(sds.getHeartRate().getState() == Sensor.SensorState.SENDING);
     assertEquals(50, sds.getHeartRate().getValue());
+    assertTrue(sds.hasPower());
+    assertTrue(sds.getPower().getState() == Sensor.SensorState.SENDING);
+    assertEquals(51, sds.getPower().getValue());
+    assertTrue(sds.hasCadence());
+    assertTrue(sds.getCadence().getState() == Sensor.SensorState.SENDING);
+    assertEquals(2, sds.getCadence().getValue());
   }
 
   public void testFindNextAlignment() {