fix typing

What to do with ARA though? Really need actual ACAS messages for
reference versus reading the spec only

.gitignore

@@ -5,9 +5,6 @@ __pycache__/
 *.py[cod]
 .pytest_cache/
 
-#cython
-*.c
-
 # C extensions
 *.so
 

pyModeS/__init__.py

@@ -10,6 +10,7 @@ except Exception:
 
 from .decoder import tell
 from .decoder import adsb
+from .decoder import acas
 from .decoder import commb
 from .decoder import allcall
 from .decoder import surv

pyModeS/decoder/acas.py

@@ -1,5 +1,158 @@
 """
 Decoding Air-Air Surveillance (ACAS) DF=0/16
-
-[To be implemented]
 """
+
+from __future__ import annotations
+
+from .. import common
+import warnings
+
+warnings.simplefilter("always", UserWarning)
+
+
+def isACAS(msg: str) -> bool:
+    """Check if the message is an ACAS coordination message.
+
+    :param msg: 28 hexdigits string
+    :return: if VDS is 3,1
+    """
+    mv = common.hex2bin(common.data(msg))
+
+    vds = mv[0:8]
+    if vds == "00110000":
+        return True
+    else:
+        return False
+
+
+def rac(msg: str) -> None | str:
+    """Resolution Advisory Complement.
+
+    :param msg: 28 hexdigits string
+    :return: RACs
+    """
+    if not isACAS(msg):
+        warnings.warn("Not an ACAS coordination message.")
+        return None
+
+    RAC = []
+
+    mv = common.hex2bin(common.data(msg))
+
+    if mv[22] == "1":
+        RAC.append("do not pass below")
+
+    if mv[23] == "1":
+        RAC.append("do not pass above")
+
+    if mv[24] == "1":
+        RAC.append("do not pass left")
+
+    if mv[25] == "1":
+        RAC.append("do not pass right")
+
+    return "; ".join(RAC)
+
+
+def rat(msg: str) -> None | int:
+    """RA terminated indicator
+
+    Mode S transponder is still required to report RA 18 seconds after
+    it is terminated by ACAS. Hence, the RAT filed is used.
+
+    :param msg: 28 hexdigits string
+    :return: if RA has been terminated
+    """
+    if not isACAS(msg):
+        warnings.warn("Not an ACAS coordination message.")
+        return None
+
+    mv = common.hex2bin(common.data(msg))
+    mte = int(mv[26])
+    return mte
+
+
+def mte(msg: str) -> None | int:
+    """Multiple threat encounter.
+
+    :param msg: 28 hexdigits string
+    :return: if there are multiple threats
+    """
+    if not isACAS(msg):
+        warnings.warn("Not an ACAS coordination message.")
+        return None
+
+    mv = common.hex2bin(common.data(msg))
+    mte = int(mv[27])
+    return mte
+
+
+def ara(msg: str) -> None | str:
+    """Decode active resolution advisory.
+
+    :param msg: 28 bytes hexadecimal message string
+    :return: RA charactristics
+    """
+    if not isACAS(msg):
+        warnings.warn("Not an ACAS coordination message.")
+        return None
+    mv = common.hex2bin(common.data(msg))
+
+    mte = int(mv[27])
+
+    ara_b1 = int(mv[8])
+    ara_b2 = int(mv[9])
+    ara_b3 = int(mv[10])
+    ara_b4 = int(mv[11])
+    ara_b5 = int(mv[12])
+    ara_b6 = int(mv[14])
+    ara_b7 = int(mv[15])
+    # ACAS III are bits 15-22
+
+    RA = []
+
+    if ara_b1 == 1:
+        if ara_b2:
+            RA.append("corrective")
+        else:
+            RA.append("preventive")
+
+        if ara_b3:
+            RA.append("downward sense")
+        else:
+            RA.append("upward sense")
+
+        if ara_b4:
+            RA.append("increased rate")
+
+        if ara_b5:
+            RA.append("sense reversal")
+
+        if ara_b6:
+            RA.append("altitude crossing")
+
+        if ara_b7:
+            RA.append("positive")
+        else:
+            RA.append("vertical speed limit")
+
+    if ara_b1 == 0 and mte == 1:
+        if ara_b2:
+            RA.append("requires a correction in the upward sense")
+
+        if ara_b3:
+            RA.append("requires a positive climb")
+
+        if ara_b4:
+            RA.append("requires a correction in downward sense")
+
+        if ara_b5:
+            RA.append("requires a positive descent")
+
+        if ara_b6:
+            RA.append("requires a crossing")
+
+        if ara_b7:
+            RA.append("requires a sense reversal")
+
+    return "; ".join(RA)

pyModeS/decoder/adsb.py

@@ -25,7 +25,7 @@ from .bds.bds06 import (
 )
 from .bds.bds08 import callsign, category
 from .bds.bds09 import airborne_velocity, altitude_diff
-from .bds.bds61 import emergency_squawk, emergency_state, is_emergency
+from .bds.bds61_st1 import emergency_squawk, emergency_state, is_emergency
 from .bds.bds62 import (
     altitude_hold_mode,
     approach_mode,
@@ -161,9 +161,7 @@ def position(
         raise RuntimeError("Incorrect or inconsistent message types")
 
 
-def position_with_ref(
-    msg: str, lat_ref: float, lon_ref: float
-) -> tuple[float, float]:
+def position_with_ref(msg: str, lat_ref: float, lon_ref: float) -> tuple[float, float]:
     """Decode position with only one message.
 
     A reference position is required, which can be previously

pyModeS/decoder/bds/__init__.py

@@ -34,14 +34,12 @@ from . import (  # noqa: F401
     bds45,
     bds50,
     bds60,
-    bds61,
+    bds61_st1,
     bds62,
 )
 
 
-def is50or60(
-    msg: str, spd_ref: float, trk_ref: float, alt_ref: float
-) -> Optional[str]:
+def is50or60(msg: str, spd_ref: float, trk_ref: float, alt_ref: float) -> Optional[str]:
     """Use reference ground speed and trk to determine BDS50 and DBS60.
 
     Args:

pyModeS/decoder/bds/bds61_st1.py

@@ -2,6 +2,7 @@
 #   BDS 6,1
 #   ADS-B TC=28
 #   Aircraft Airborne status
+#   (Subtype 1)
 # ------------------------------------------
 
 from ... import common

pyModeS/decoder/bds/bds61_st2.py

@@ -0,0 +1,102 @@
+# ------------------------------------------
+#   BDS 6,1
+#   ADS-B TC=28
+#   Aircraft Airborne status
+#   (Subtype 1)
+# ------------------------------------------
+
+from __future__ import annotations
+
+from ... import common
+from .. import acas
+
+
+def threat_type(msg: str) -> int:
+    """Determine the threat type indicator.
+
+    Value    Meaning
+    -----    ---------------------------------------
+    0        No identity data in TID
+    1        TID has Mode S address (ICAO)
+    2        TID has altitude, range, and bearing
+    3        Not assigned
+
+    :param msg: 28 hexdigits string
+    :return: indicator of threat type
+    """
+    mb = common.hex2bin(common.data(msg))
+    tti = common.bin2int(mb[28:30])
+    return tti
+
+
+def threat_identity(msg: str) -> str:
+    mb = common.hex2bin(common.data(msg))
+    tti = threat_type(msg)
+
+    # The ICAO of the threat is announced
+    if tti == 1:
+        return common.icao(mb[30:55])
+    else:
+        raise RuntimeError("%s: Missing threat identity (ICAO)")
+
+
+def threat_location(msg: str) -> None | tuple[int, int, int]:
+    """Get the altitude, range, and bearing of the threat.
+
+    Altitude is the Mode C altitude
+
+    :param msg: 28 hexdigits string
+    :return: tuple of the Mode C altitude, range, and bearing
+    """
+    mb = common.hex2bin(common.data(msg))
+    tti = threat_type(msg)
+
+    # Altitude, range, and bearing of threat
+    if tti == 2:
+        altitude = common.altitude(mb[31:44])
+        distance = common.bin2int(mb[44:51])
+        bearing = common.bin2int(mb[51:57])
+        return altitude, distance, bearing
+
+    return None
+
+
+def has_multiple_threats(msg: str) -> bool:
+    """Indicate if the ACAS is processing multiple threats simultaneously.
+
+    :param msg: 28 hexdigits string
+    :return: if there are multiple threats
+    """
+    return acas.mte(msg) == 1
+
+
+def active_resolution_advisories(msg: str) -> None | str:
+    """Decode active resolution advisory.
+
+    Uses ARA decoding function from ACAS module.
+
+    :param msg: 28 bytes hexadecimal message string
+    :return: RA charactristics
+    """
+    return acas.ara(msg)
+
+
+def is_ra_terminated(msg: str) -> bool:
+    """Indicate if the threat is still being generated.
+
+    Mode S transponder is still required to report RA 18 seconds after
+    it is terminated by ACAS. Hence, the RAT filed is used.
+
+    :param msg: 28 hexdigits string
+    :return: if the threat is terminated
+    """
+    return acas.rat(msg) == 1
+
+
+def ra_complement(msg: str) -> None | str:
+    """Resolution Advisory Complement.
+
+    :param msg: 28 hexdigits string
+    :return: RACs
+    """
+    return acas.rac(msg)

tests/test_acas.py

@@ -0,0 +1,40 @@
+import pyModeS as pms
+
+msgs = [
+    "80E1983958C392E8710C642D0BAD",
+    "8609F8E19E90653083FDE096BE26",
+    "80011B41F40017D0000012E06B45",
+    "808182365813667446EB715E253D",
+    "80E1953058AB029BE8F4E60D989E",
+    "8667ECFA8FE06B30E59A124D5AEF",
+    "80030AA000042C0AD05D6205DB2C",
+    "8631A80000373C463B6E7A00008B",
+    "80E19131588B146108DE703F3C47",
+    "825CC4A0001595C4600030A40000",
+    "808182365813667438EB710EB6D8",
+    "80A18393581D3655E90354A664B2",
+    "8081823658136309B4F22BCB5F8D",
+    "80E1953058AB06516E8602756DD8",
+    "80E1991058C9063AB6A3E4744DC3",
+    "8073EC91840AFCED8F300BE765C5",
+    "8571F54AA814BF8130066A19A31D",
+    "864070E1990D3B1E78048BAE6987",
+    "80E1991058C9063AB6A3E4744DC3",
+    "80818298581581F7CAF8C3C1EEA4",
+    "80004E98BC90000FF01010951298",
+    "8526D57E4D963C92CDEE1B6C7C49",
+    "802A613C93F65A7FF803A51B5ADB",
+    "85B6C54279B67BE2A0001998FFDA",
+    "851944F15881648338D1AF4B7A27",
+    "8321014858208000787905B0E800",
+    "866DD078EDEBD330404FFFAE9BA5",
+    "80E196905AB503260E835D849E35",
+]
+
+for msg in msgs:
+    print("-" * 80)
+    print(msg)
+    print("ARA", pms.acas.ara(msg))
+    print("RAC", pms.acas.rac(msg))
+    print("MTE", pms.acas.mte(msg))
+    print("RAT", pms.acas.rat(msg))