update BDS 4,4 decoder, default to revised version

pyModeS/ehs.py

@@ -209,36 +209,38 @@ def pbaro(msg):
 # DF 20/21, BDS 4,4
 # ------------------------------------------
 
-def isBDS44(msg):
+def isBDS44(msg, rev=True):
     """Check if a message is likely to be BDS code 4,4
     Meteorological routine air report
 
-    WARNING: there is two different definition for BDS4,4. This part of the
-    decoder is likely to be wrong...
-
     Args:
         msg (String): 28 bytes hexadecimal message string
+        rev (bool): using revised version
 
     Returns:
         bool: True or False
     """
 
-    # status bit 5, 15, 24, 36, 49
     d = util.hex2bin(data(msg))
 
     result = True
 
-    # --- current version ---
+    if not rev:
-    result = result & checkbits(d, 5, 6, 23) \
+        # status bit 5, 35, 47, 50
-        & checkbits(d, 35, 36, 46) & checkbits(d, 47, 48, 49) \
+        result = result & checkbits(d, 5, 6, 23) \
-        & checkbits(d, 50, 51, 56)
+            & checkbits(d, 35, 36, 46) & checkbits(d, 47, 48, 49) \
+            & checkbits(d, 50, 51, 56)
 
-    # # --- revised future version ---
-    # result = result & checkbits(d, 5, 6, 14) \
-    #     & checkbits(d, 15, 16, 23) & checkbits(d, 24, 25, 35) \
-    #     & checkbits(d, 36, 37, 47) & checkbits(d, 49, 50, 56)
 
-    if wind(msg) and wind(msg)[0] > 250:
+    else:
+        # status bit 5, 15, 24, 36, 49
+
+        result = result & checkbits(d, 5, 6, 14) \
+            & checkbits(d, 15, 16, 23) & checkbits(d, 24, 25, 35) \
+            & checkbits(d, 36, 37, 47) & checkbits(d, 49, 50, 56)
+
+    vw = wind(msg, rev=rev)
+    if vw and vw[0] > 250:
         result &= False
 
     # if temperature(msg):
@@ -248,78 +250,123 @@ def isBDS44(msg):
     return result
 
 
-def wind(msg):
+def wind(msg, rev=True):
     """reported wind speed and direction
 
     Args:
         msg (String): 28 bytes hexadecimal message (BDS44) string
+        rev (bool): using revised version
 
     Returns:
         (int, float): speed (kt), direction (degree)
     """
     d = util.hex2bin(data(msg))
 
-    status = int(d[4])
+    if not rev:
-    if not status:
+        status = int(d[4])
-        return None
+        if not status:
+            return None
+
+        speed = util.bin2int(d[5:14])   # knots
+        direction = util.bin2int(d[14:23]) * 180.0 / 256.0  # degree
+
+    else:
+        spd_status = int(d[4])
+        dir_status = int(d[14])
+
+        if (not spd_status) or (not dir_status):
+            return None
+
+        speed = util.bin2int(d[5:14])   # knots
+        direction = util.bin2int(d[15:23]) * 180.0 / 128.0  # degree
 
-    speed = util.bin2int(d[5:14])   # knots
-    direction = util.bin2int(d[14:23]) * 180.0 / 256.0  # degree
     return round(speed, 0), round(direction, 1)
 
 
-def temperature(msg):
+def temperature(msg, rev=True):
     """reported air temperature
 
     Args:
         msg (String): 28 bytes hexadecimal message (BDS44) string
+        rev (bool): using revised version
 
     Returns:
         float: tmeperature in Celsius degree
     """
     d = util.hex2bin(data(msg))
 
-    sign = int(d[23])    # 1 -> minus
+    if not rev:
-    temp = util.bin2int(d[24:34]) * 0.25   # celsius
+        sign = int(d[23])
-    temp = round(temp, 1)
+        temp = util.bin2int(d[24:34]) * 0.125   # celsius
-    return -1 * temp if sign else temp
+        temp = round(temp, 1)
+
+    else:
+        status = int(d[23])
+        if not status:
+            return None
+
+        sign = int(d[24])
+        temp = util.bin2int(d[25:35]) * 0.125   # celsius
+        temp = round(temp, 1)
+
+    return temp if sign else -1*temp
 
 
-def pressure(msg):
+def pressure(msg, rev=True):
     """reported average static pressure
 
     Args:
         msg (String): 28 bytes hexadecimal message (BDS44) string
+        rev (bool): using revised version
 
     Returns:
         int: static pressure in hPa
     """
     d = util.hex2bin(data(msg))
 
-    status = int(d[34])
+    if not rev:
-    if not status:
+        status = int(d[34])
-        return None
+        if not status:
+            return None
+
+        p = util.bin2int(d[35:46])    # hPa
+
+    else:
+        status = int(d[35])
+        if not status:
+            return None
+
+        p = util.bin2int(d[36:47])    # hPa
 
-    p = util.bin2int(d[35:46])    # hPa
     return p
 
 
-def humidity(msg):
+def humidity(msg, rev=True):
     """reported humidity
 
     Args:
         msg (String): 28 bytes hexadecimal message (BDS44) string
+        rev (bool): using revised version
 
     Returns:
         float: percentage of humidity, [0 - 100] %
     """
     d = util.hex2bin(data(msg))
 
-    status = int(d[49])
+    if not rev:
-    if not status:
+        status = int(d[49])
-        return None
+        if not status:
+            return None
+
+        hm = util.bin2int(d[50:56]) * 100.0 / 64    # %
+
+    else:
+        status = int(d[48])
+        if not status:
+            return None
+
+        hm = util.bin2int(d[49:56])    # %
 
-    hm = util.bin2int(d[50:56]) * 100.0 / 64    # %
     return round(hm, 1)
 
 

tests/sample_data_test.py

@@ -62,7 +62,8 @@ def ehs_decode_all(n=None):
                       ehs.alt_fms(m), ehs.pbaro(m))
 
             if vBDS == "BDS44":
-                print(ts, m, icao, vBDS, ehs.wind(m))
+                print(ts, m, icao, vBDS, ehs.wind(m),
+                      ehs.temperature(m), ehs.pressure(m))
 
             if vBDS == "BDS50":
                 print(ts, m, icao, vBDS, ehs.roll(m), ehs.track(m),