Merge branch 'tuftedocelot-bds-61'

pyModeS/decoder/adsb.py

@@ -28,6 +28,7 @@ from pyModeS.decoder.bds.bds06 import (
 )
 from pyModeS.decoder.bds.bds08 import category, callsign
 from pyModeS.decoder.bds.bds09 import airborne_velocity, altitude_diff
+from pyModeS.decoder.bds.bds61 import is_emergency, emergency_state, emergency_squawk
 
 
 def df(msg):

pyModeS/decoder/bds/bds61.py

@@ -0,0 +1,83 @@
+# ------------------------------------------
+#   BDS 6,1
+#   ADS-B TC=28
+#   Aircraft Airborne status
+# ------------------------------------------
+
+from pyModeS import common
+
+
+def is_emergency(msg: str) -> bool:
+    """Check if the aircraft is reporting an emergency.
+
+    Non-emergencies are either a subtype of zero (no information) or
+    subtype of one and a value of zero (no emergency).
+    Subtype = 2 indicates an ACAS RA broadcast, look in BDS 3,0
+
+    :param msg: 28 bytes hexadecimal message string
+    :return: if the aircraft has declared an emergency
+    """
+    if common.typecode(msg) != 28:
+        raise RuntimeError("%s: Not an airborne status message, expecting TC=28" % msg)
+
+    mb = common.hex2bin(msg)[32:]
+    subtype = common.bin2int(mb[5:8])
+
+    if subtype == 2:
+        raise RuntimeError("%s: Emergency message is ACAS-RA, not implemented")
+
+    emergency_state = common.bin2int(mb[8:11])
+
+    if subtype == 1 and emergency_state == 1:
+        return True
+    else:
+        return False
+
+
+def emergency_state(msg: str) -> int:
+    """Decode aircraft emergency state.
+
+    Value   Meaning
+    -----   -----------------------
+    0       No emergency
+    1       General emergency
+    2       Lifeguard/Medical
+    3       Minimum fuel
+    4       No communications
+    5       Unlawful communications
+    6-7     Reserved
+
+    :param msg: 28 bytes hexadecimal message string
+    :return: emergency state
+    """
+
+    mb = common.hex2bin(msg)[32:]
+    subtype = common.bin2int(mb[5:8])
+
+    if subtype == 2:
+        raise RuntimeError("%s: Emergency message is ACAS-RA, not implemented")
+
+    emergency_state = common.bin2int(mb[8:11])
+    return emergency_state
+
+
+def emergency_squawk(msg: str) -> str:
+    """Decode squawk code.
+
+    Emergency value 1: squawk 7700.
+    Emergency value 4: squawk 7600.
+    Emergency value 5: squawk 7500.
+
+    :param msg: 28 bytes hexadecimal message string
+    :return: aircraft squawk code
+    """
+    if common.typecode(msg) != 28:
+        raise RuntimeError("%s: Not an airborne status message, expecting TC=28" % msg)
+
+    msgbin = common.hex2bin(msg)
+
+    # construct the 13 bits Mode A ID code
+    idcode = msgbin[43:49] + "0" + msgbin[49:55]
+
+    squawk = common.squawk(idcode)
+    return squawk

tests/test_adsb.py

@@ -80,6 +80,12 @@ def test_adsb_velocity():
     assert adsb.altitude_diff("8D485020994409940838175B284F") == 550
 
 
+def test_adsb_emergency():
+    assert not adsb.is_emergency("8DA2C1B6E112B600000000760759")
+    assert adsb.emergency_state("8DA2C1B6E112B600000000760759") == 0
+    assert adsb.emergency_squawk("8DA2C1B6E112B600000000760759") == "6615"
+
+
 # def test_nic():
 #     assert adsb.nic('8D3C70A390AB11F55B8C57F65FE6') == 0
 #     assert adsb.nic('8DE1C9738A4A430B427D219C8225') == 1