Fixed TCAS version in BDS1,0 (DataLinkCapabilityReport)

The method interpreted bit 39 and 40 in the wrong order. See DO-181E, Table B-3-16 Fixes #26
SeRoSystems · Dec 4, 2024 · f88f2d8 · f88f2d8
1 parent e157daa
commit f88f2d8
Show file tree

Hide file tree

Showing 2 changed files with 41 additions and 2 deletions.
diff --git a/src/main/java/de/serosystems/lib1090/msgs/bds/DataLinkCapabilityReport.java b/src/main/java/de/serosystems/lib1090/msgs/bds/DataLinkCapabilityReport.java
@@ -421,7 +421,7 @@ static boolean extractTcasRataCapability(byte[] message) {
     }
 
     static short extractTcasVersionNumber(byte[] message) {
-        return (short) (message[4] & 0x03);
+        return (short) ( ((message[4]<<1) & 0x02) | ((message[4]>>>1) & 0x01) );
     }
 
     static boolean extractBasicDataFlashCapability(byte[] message) {

diff --git a/src/test/java/de/serosystems/lib1090/msgs/bds/DataLinkCapabilityReportTest.java b/src/test/java/de/serosystems/lib1090/msgs/bds/DataLinkCapabilityReportTest.java
@@ -106,7 +106,7 @@ public void tcasRataCapability() {
 
     @Test
     public void tcasVersionNumber() {
-        assertEquals(1, DataLinkCapabilityReport.extractTcasVersionNumber(msg));
+        assertEquals(2, DataLinkCapabilityReport.extractTcasVersionNumber(msg));
     }
 
     @Test
@@ -139,4 +139,43 @@ public void extractChangeFlag() {
         assertTrue(DataLinkCapabilityReport.extractChangeFlag(msg));
     }
 
+    @Test
+    void tcacsVersion0() {
+       byte[] message =  new byte[]{
+               (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff,
+               (byte) 0b11111100,
+               (byte) 0xff, (byte) 0xff
+       };
+        assertEquals(0, DataLinkCapabilityReport.extractTcasVersionNumber(message));
+    }
+
+    @Test
+    void tcacsVersion1() {
+        byte[] message =  new byte[]{
+                (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff,
+                (byte) 0b11111110,
+                (byte) 0xff, (byte) 0xff
+        };
+        assertEquals(1, DataLinkCapabilityReport.extractTcasVersionNumber(message));
+    }
+
+    @Test
+    void tcacsVersion2() {
+        byte[] message =  new byte[]{
+                (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff,
+                (byte) 0b11111101,
+                (byte) 0xff, (byte) 0xff
+        };
+        assertEquals(2, DataLinkCapabilityReport.extractTcasVersionNumber(message));
+    }
+
+    @Test
+    void tcacsVersion3() {
+        byte[] message =  new byte[]{
+                (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff,
+                (byte) 0b11111111,
+                (byte) 0xff, (byte) 0xff
+        };
+        assertEquals(3, DataLinkCapabilityReport.extractTcasVersionNumber(message));
+    }
 }