diff --git a/pyModeS/decoder/__init__.py b/pyModeS/decoder/__init__.py
index 10bacc8..c56a9b1 100644
--- a/pyModeS/decoder/__init__.py
+++ b/pyModeS/decoder/__init__.py
@@ -1,9 +1,9 @@
 from __future__ import absolute_import, print_function, division
 
-from pyModeS.decoder import adsb, commb, common, bds
-
 
 def tell(msg):
+    from pyModeS import common, adsb, commb, bds
+
     def _print(label, value, unit=None):
         print("%20s: " % label, end="")
         print("%s " % value, end="")
diff --git a/pyModeS/decoder/acas.py b/pyModeS/decoder/acas.py
index e22759b..91cf634 100644
--- a/pyModeS/decoder/acas.py
+++ b/pyModeS/decoder/acas.py
@@ -3,6 +3,3 @@ Decoding Air-Air Surveillance (ACAS) DF=0/16
 
 [To be implemented]
 """
-
-from __future__ import absolute_import, print_function, division
-from pyModeS.decoder import common
diff --git a/pyModeS/decoder/adsb.py b/pyModeS/decoder/adsb.py
index d28d77a..41a92ca 100644
--- a/pyModeS/decoder/adsb.py
+++ b/pyModeS/decoder/adsb.py
@@ -16,7 +16,9 @@ The ADS-B wrapper also imports functions from the following modules:
 from __future__ import absolute_import, print_function, division
 
 import pyModeS as pms
-from pyModeS.decoder import common
+
+from pyModeS import common
+
 from pyModeS.decoder import uncertainty
 
 # from pyModeS.decoder.bds import bds05, bds06, bds09
diff --git a/pyModeS/decoder/allcall.py b/pyModeS/decoder/allcall.py
index 1901698..6e296ca 100644
--- a/pyModeS/decoder/allcall.py
+++ b/pyModeS/decoder/allcall.py
@@ -3,6 +3,3 @@ Decoding all call replies DF=11
 
 [To be implemented]
 """
-
-from __future__ import absolute_import, print_function, division
-from pyModeS.decoder import common
diff --git a/pyModeS/decoder/bds/__init__.py b/pyModeS/decoder/bds/__init__.py
index 69bf254..baea5b5 100644
--- a/pyModeS/decoder/bds/__init__.py
+++ b/pyModeS/decoder/bds/__init__.py
@@ -22,7 +22,13 @@ from __future__ import absolute_import, print_function, division
 import numpy as np
 
 from pyModeS.extra import aero
-from pyModeS.decoder import common
+
+try:
+    from pyModeS.decoder import c_common as common
+except:
+    from pyModeS.decoder import common
+
+
 from pyModeS.decoder.bds import (
     bds05,
     bds06,
diff --git a/pyModeS/decoder/bds/bds05.py b/pyModeS/decoder/bds/bds05.py
index dce5742..ed9575f 100644
--- a/pyModeS/decoder/bds/bds05.py
+++ b/pyModeS/decoder/bds/bds05.py
@@ -6,7 +6,8 @@
 
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder import common
+
+from pyModeS import common
 
 
 def airborne_position(msg0, msg1, t0, t1):
diff --git a/pyModeS/decoder/bds/bds06.py b/pyModeS/decoder/bds/bds06.py
index d882569..17c3fa1 100644
--- a/pyModeS/decoder/bds/bds06.py
+++ b/pyModeS/decoder/bds/bds06.py
@@ -5,8 +5,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder import common
-import math
+
+from pyModeS import common
 
 
 def surface_position(msg0, msg1, t0, t1, lat_ref, lon_ref):
diff --git a/pyModeS/decoder/bds/bds08.py b/pyModeS/decoder/bds/bds08.py
index bdd7106..8bc03ae 100644
--- a/pyModeS/decoder/bds/bds08.py
+++ b/pyModeS/decoder/bds/bds08.py
@@ -5,7 +5,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder import common
+
+from pyModeS import common
 
 
 def category(msg):
diff --git a/pyModeS/decoder/bds/bds09.py b/pyModeS/decoder/bds/bds09.py
index 1a26ca6..aea62c8 100644
--- a/pyModeS/decoder/bds/bds09.py
+++ b/pyModeS/decoder/bds/bds09.py
@@ -6,6 +6,10 @@
 
 from __future__ import absolute_import, print_function, division
 from pyModeS.decoder import common
+
+from pyModeS import common
+
+
 import math
 
 
diff --git a/pyModeS/decoder/bds/bds10.py b/pyModeS/decoder/bds/bds10.py
index 02cb658..7d51c34 100644
--- a/pyModeS/decoder/bds/bds10.py
+++ b/pyModeS/decoder/bds/bds10.py
@@ -4,7 +4,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros
+
+from pyModeS import common
 
 
 def is10(msg):
@@ -17,23 +18,23 @@ def is10(msg):
         bool: True or False
     """
 
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     # first 8 bits must be 0x10
     if d[0:8] != "00010000":
         return False
 
     # bit 10 to 14 are reserved
-    if bin2int(d[9:14]) != 0:
+    if common.bin2int(d[9:14]) != 0:
         return False
 
     # overlay capability conflict
-    if d[14] == "1" and bin2int(d[16:23]) < 5:
+    if d[14] == "1" and common.bin2int(d[16:23]) < 5:
         return False
-    if d[14] == "0" and bin2int(d[16:23]) > 4:
+    if d[14] == "0" and common.bin2int(d[16:23]) > 4:
         return False
 
     return True
@@ -48,6 +49,6 @@ def ovc10(msg):
     Returns:
         int: Whether the transponder is OVC capable
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     return int(d[14])
diff --git a/pyModeS/decoder/bds/bds17.py b/pyModeS/decoder/bds/bds17.py
index 5614fce..8dcc2fa 100644
--- a/pyModeS/decoder/bds/bds17.py
+++ b/pyModeS/decoder/bds/bds17.py
@@ -5,7 +5,8 @@
 
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros
+
+from pyModeS import common
 
 
 def is17(msg):
@@ -18,12 +19,12 @@ def is17(msg):
         bool: True or False
     """
 
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
-    if bin2int(d[28:56]) != 0:
+    if common.bin2int(d[28:56]) != 0:
         return False
 
     caps = cap17(msg)
@@ -80,7 +81,7 @@ def cap17(msg):
         "E2",
     ]
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
     idx = [i for i, v in enumerate(d[:28]) if v == "1"]
     capacity = ["BDS" + allbds[i] for i in idx if allbds[i] is not "NA"]
 
diff --git a/pyModeS/decoder/bds/bds20.py b/pyModeS/decoder/bds/bds20.py
index 32ced8c..6c3dcfd 100644
--- a/pyModeS/decoder/bds/bds20.py
+++ b/pyModeS/decoder/bds/bds20.py
@@ -4,7 +4,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros
+
+from pyModeS import common
 
 
 def is20(msg):
@@ -17,10 +18,10 @@ def is20(msg):
         bool: True or False
     """
 
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[0:8] != "00100000":
         return False
@@ -44,16 +45,16 @@ def cs20(msg):
     """
     chars = "#ABCDEFGHIJKLMNOPQRSTUVWXYZ#####_###############0123456789######"
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     cs = ""
-    cs += chars[bin2int(d[8:14])]
-    cs += chars[bin2int(d[14:20])]
-    cs += chars[bin2int(d[20:26])]
-    cs += chars[bin2int(d[26:32])]
-    cs += chars[bin2int(d[32:38])]
-    cs += chars[bin2int(d[38:44])]
-    cs += chars[bin2int(d[44:50])]
-    cs += chars[bin2int(d[50:56])]
+    cs += chars[common.bin2int(d[8:14])]
+    cs += chars[common.bin2int(d[14:20])]
+    cs += chars[common.bin2int(d[20:26])]
+    cs += chars[common.bin2int(d[26:32])]
+    cs += chars[common.bin2int(d[32:38])]
+    cs += chars[common.bin2int(d[38:44])]
+    cs += chars[common.bin2int(d[44:50])]
+    cs += chars[common.bin2int(d[50:56])]
 
     return cs
diff --git a/pyModeS/decoder/bds/bds30.py b/pyModeS/decoder/bds/bds30.py
index 59a7a9a..53c1ee9 100644
--- a/pyModeS/decoder/bds/bds30.py
+++ b/pyModeS/decoder/bds/bds30.py
@@ -4,7 +4,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros
+
+from pyModeS import common
 
 
 def is30(msg):
@@ -17,10 +18,10 @@ def is30(msg):
         bool: True or False
     """
 
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[0:8] != "00110000":
         return False
@@ -30,7 +31,7 @@ def is30(msg):
         return False
 
     # reserved for ACAS III, in far future
-    if bin2int(d[15:22]) >= 48:
+    if common.bin2int(d[15:22]) >= 48:
         return False
 
     return True
diff --git a/pyModeS/decoder/bds/bds40.py b/pyModeS/decoder/bds/bds40.py
index a9891ad..008505b 100644
--- a/pyModeS/decoder/bds/bds40.py
+++ b/pyModeS/decoder/bds/bds40.py
@@ -5,7 +5,8 @@
 
 from __future__ import absolute_import, print_function, division
 import warnings
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros, wrongstatus
+
+from pyModeS import common
 
 
 def is40(msg):
@@ -18,34 +19,34 @@ def is40(msg):
         bool: True or False
     """
 
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     # status bit 1, 14, and 27
 
-    if wrongstatus(d, 1, 2, 13):
+    if common.wrongstatus(d, 1, 2, 13):
         return False
 
-    if wrongstatus(d, 14, 15, 26):
+    if common.wrongstatus(d, 14, 15, 26):
         return False
 
-    if wrongstatus(d, 27, 28, 39):
+    if common.wrongstatus(d, 27, 28, 39):
         return False
 
-    if wrongstatus(d, 48, 49, 51):
+    if common.wrongstatus(d, 48, 49, 51):
         return False
 
-    if wrongstatus(d, 54, 55, 56):
+    if common.wrongstatus(d, 54, 55, 56):
         return False
 
     # bits 40-47 and 52-53 shall all be zero
 
-    if bin2int(d[39:47]) != 0:
+    if common.bin2int(d[39:47]) != 0:
         return False
 
-    if bin2int(d[51:53]) != 0:
+    if common.bin2int(d[51:53]) != 0:
         return False
 
     return True
@@ -60,12 +61,12 @@ def selalt40mcp(msg):
     Returns:
         int: altitude in feet
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[0] == "0":
         return None
 
-    alt = bin2int(d[1:13]) * 16  # ft
+    alt = common.bin2int(d[1:13]) * 16  # ft
     return alt
 
 
@@ -78,12 +79,12 @@ def selalt40fms(msg):
     Returns:
         int: altitude in feet
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[13] == "0":
         return None
 
-    alt = bin2int(d[14:26]) * 16  # ft
+    alt = common.bin2int(d[14:26]) * 16  # ft
     return alt
 
 
@@ -96,12 +97,12 @@ def p40baro(msg):
     Returns:
         float: pressure in millibar
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[26] == "0":
         return None
 
-    p = bin2int(d[27:39]) * 0.1 + 800  # millibar
+    p = common.bin2int(d[27:39]) * 0.1 + 800  # millibar
     return p
 
 
diff --git a/pyModeS/decoder/bds/bds44.py b/pyModeS/decoder/bds/bds44.py
index 7bd59eb..1ee5492 100644
--- a/pyModeS/decoder/bds/bds44.py
+++ b/pyModeS/decoder/bds/bds44.py
@@ -4,7 +4,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros, wrongstatus
+
+from pyModeS import common
 
 
 def is44(msg):
@@ -19,26 +20,26 @@ def is44(msg):
         bool: True or False
 
     """
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     # status bit 5, 35, 47, 50
-    if wrongstatus(d, 5, 6, 23):
+    if common.wrongstatus(d, 5, 6, 23):
         return False
 
-    if wrongstatus(d, 35, 36, 46):
+    if common.wrongstatus(d, 35, 36, 46):
         return False
 
-    if wrongstatus(d, 47, 48, 49):
+    if common.wrongstatus(d, 47, 48, 49):
         return False
 
-    if wrongstatus(d, 50, 51, 56):
+    if common.wrongstatus(d, 50, 51, 56):
         return False
 
     # Bits 1-4 indicate source, values > 4 reserved and should not occur
-    if bin2int(d[0:4]) > 4:
+    if common.bin2int(d[0:4]) > 4:
         return False
 
     vw, dw = wind44(msg)
@@ -62,14 +63,14 @@ def wind44(msg):
         (int, float): speed (kt), direction (degree)
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     status = int(d[4])
     if not status:
         return None, None
 
-    speed = bin2int(d[5:14])  # knots
-    direction = bin2int(d[14:23]) * 180.0 / 256.0  # degree
+    speed = common.bin2int(d[5:14])  # knots
+    direction = common.bin2int(d[14:23]) * 180.0 / 256.0  # degree
 
     return round(speed, 0), round(direction, 1)
 
@@ -86,10 +87,10 @@ def temp44(msg):
             error in ICAO 9871 (2008) Appendix A-67.
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     sign = int(d[23])
-    value = bin2int(d[24:34])
+    value = common.bin2int(d[24:34])
 
     if sign:
         value = value - 1024
@@ -113,12 +114,12 @@ def p44(msg):
         int: static pressure in hPa
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[34] == "0":
         return None
 
-    p = bin2int(d[35:46])  # hPa
+    p = common.bin2int(d[35:46])  # hPa
 
     return p
 
@@ -132,12 +133,12 @@ def hum44(msg):
     Returns:
         float: percentage of humidity, [0 - 100] %
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[49] == "0":
         return None
 
-    hm = bin2int(d[50:56]) * 100.0 / 64  # %
+    hm = common.bin2int(d[50:56]) * 100.0 / 64  # %
 
     return round(hm, 1)
 
@@ -152,11 +153,11 @@ def turb44(msg):
         int: turbulence level. 0=NIL, 1=Light, 2=Moderate, 3=Severe
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[46] == "0":
         return None
 
-    turb = bin2int(d[47:49])
+    turb = common.bin2int(d[47:49])
 
     return turb
diff --git a/pyModeS/decoder/bds/bds45.py b/pyModeS/decoder/bds/bds45.py
index adf3197..2c581ae 100644
--- a/pyModeS/decoder/bds/bds45.py
+++ b/pyModeS/decoder/bds/bds45.py
@@ -4,7 +4,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros, wrongstatus
+
+from pyModeS import common
 
 
 def is45(msg):
@@ -19,38 +20,38 @@ def is45(msg):
         bool: True or False
 
     """
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     # status bit 1, 4, 7, 10, 13, 16, 27, 39
-    if wrongstatus(d, 1, 2, 3):
+    if common.wrongstatus(d, 1, 2, 3):
         return False
 
-    if wrongstatus(d, 4, 5, 6):
+    if common.wrongstatus(d, 4, 5, 6):
         return False
 
-    if wrongstatus(d, 7, 8, 9):
+    if common.wrongstatus(d, 7, 8, 9):
         return False
 
-    if wrongstatus(d, 10, 11, 12):
+    if common.wrongstatus(d, 10, 11, 12):
         return False
 
-    if wrongstatus(d, 13, 14, 15):
+    if common.wrongstatus(d, 13, 14, 15):
         return False
 
-    if wrongstatus(d, 16, 17, 26):
+    if common.wrongstatus(d, 16, 17, 26):
         return False
 
-    if wrongstatus(d, 27, 28, 38):
+    if common.wrongstatus(d, 27, 28, 38):
         return False
 
-    if wrongstatus(d, 39, 40, 51):
+    if common.wrongstatus(d, 39, 40, 51):
         return False
 
     # reserved
-    if bin2int(d[51:56]) != 0:
+    if common.bin2int(d[51:56]) != 0:
         return False
 
     temp = temp45(msg)
@@ -71,11 +72,11 @@ def turb45(msg):
         int: Turbulence level. 0=NIL, 1=Light, 2=Moderate, 3=Severe
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
     if d[0] == "0":
         return None
 
-    turb = bin2int(d[1:3])
+    turb = common.bin2int(d[1:3])
     return turb
 
 
@@ -89,11 +90,11 @@ def ws45(msg):
         int: Wind shear level. 0=NIL, 1=Light, 2=Moderate, 3=Severe
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
     if d[3] == "0":
         return None
 
-    ws = bin2int(d[4:6])
+    ws = common.bin2int(d[4:6])
     return ws
 
 
@@ -107,11 +108,11 @@ def mb45(msg):
         int: Microburst level. 0=NIL, 1=Light, 2=Moderate, 3=Severe
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
     if d[6] == "0":
         return None
 
-    mb = bin2int(d[7:9])
+    mb = common.bin2int(d[7:9])
     return mb
 
 
@@ -125,11 +126,11 @@ def ic45(msg):
         int: Icing level. 0=NIL, 1=Light, 2=Moderate, 3=Severe
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
     if d[9] == "0":
         return None
 
-    ic = bin2int(d[10:12])
+    ic = common.bin2int(d[10:12])
     return ic
 
 
@@ -143,11 +144,11 @@ def wv45(msg):
         int: Wake vortex level. 0=NIL, 1=Light, 2=Moderate, 3=Severe
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
     if d[12] == "0":
         return None
 
-    ws = bin2int(d[13:15])
+    ws = common.bin2int(d[13:15])
     return ws
 
 
@@ -161,10 +162,10 @@ def temp45(msg):
         float: tmeperature in Celsius degree
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     sign = int(d[16])
-    value = bin2int(d[17:26])
+    value = common.bin2int(d[17:26])
 
     if sign:
         value = value - 512
@@ -185,10 +186,10 @@ def p45(msg):
         int: static pressure in hPa
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
     if d[26] == "0":
         return None
-    p = bin2int(d[27:38])  # hPa
+    p = common.bin2int(d[27:38])  # hPa
     return p
 
 
@@ -202,8 +203,8 @@ def rh45(msg):
         int: radio height in ft
 
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
     if d[38] == "0":
         return None
-    rh = bin2int(d[39:51]) * 16
+    rh = common.bin2int(d[39:51]) * 16
     return rh
diff --git a/pyModeS/decoder/bds/bds50.py b/pyModeS/decoder/bds/bds50.py
index 91ec924..2d16f63 100644
--- a/pyModeS/decoder/bds/bds50.py
+++ b/pyModeS/decoder/bds/bds50.py
@@ -4,7 +4,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros, wrongstatus
+
+from pyModeS import common
 
 
 def is50(msg):
@@ -18,26 +19,26 @@ def is50(msg):
         bool: True or False
     """
 
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     # status bit 1, 12, 24, 35, 46
 
-    if wrongstatus(d, 1, 3, 11):
+    if common.wrongstatus(d, 1, 3, 11):
         return False
 
-    if wrongstatus(d, 12, 13, 23):
+    if common.wrongstatus(d, 12, 13, 23):
         return False
 
-    if wrongstatus(d, 24, 25, 34):
+    if common.wrongstatus(d, 24, 25, 34):
         return False
 
-    if wrongstatus(d, 35, 36, 45):
+    if common.wrongstatus(d, 35, 36, 45):
         return False
 
-    if wrongstatus(d, 46, 47, 56):
+    if common.wrongstatus(d, 46, 47, 56):
         return False
 
     roll = roll50(msg)
@@ -68,13 +69,13 @@ def roll50(msg):
         float: angle in degrees,
                negative->left wing down, positive->right wing down
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[0] == "0":
         return None
 
     sign = int(d[1])  # 1 -> left wing down
-    value = bin2int(d[2:11])
+    value = common.bin2int(d[2:11])
 
     if sign:
         value = value - 512
@@ -92,13 +93,13 @@ def trk50(msg):
     Returns:
         float: angle in degrees to true north (from 0 to 360)
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[11] == "0":
         return None
 
     sign = int(d[12])  # 1 -> west
-    value = bin2int(d[13:23])
+    value = common.bin2int(d[13:23])
 
     if sign:
         value = value - 1024
@@ -121,12 +122,12 @@ def gs50(msg):
     Returns:
         int: ground speed in knots
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[23] == "0":
         return None
 
-    spd = bin2int(d[24:34]) * 2  # kts
+    spd = common.bin2int(d[24:34]) * 2  # kts
     return spd
 
 
@@ -139,7 +140,7 @@ def rtrk50(msg):
     Returns:
         float: angle rate in degrees/second
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[34] == "0":
         return None
@@ -148,7 +149,7 @@ def rtrk50(msg):
         return None
 
     sign = int(d[35])  # 1 -> negative value, two's complement
-    value = bin2int(d[36:45])
+    value = common.bin2int(d[36:45])
     if sign:
         value = value - 512
 
@@ -165,10 +166,10 @@ def tas50(msg):
     Returns:
         int: true airspeed in knots
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[45] == "0":
         return None
 
-    tas = bin2int(d[46:56]) * 2  # kts
+    tas = common.bin2int(d[46:56]) * 2  # kts
     return tas
diff --git a/pyModeS/decoder/bds/bds53.py b/pyModeS/decoder/bds/bds53.py
index 6673489..8b8a8df 100644
--- a/pyModeS/decoder/bds/bds53.py
+++ b/pyModeS/decoder/bds/bds53.py
@@ -4,7 +4,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros, wrongstatus
+
+from pyModeS import common
 
 
 def is53(msg):
@@ -18,26 +19,26 @@ def is53(msg):
         bool: True or False
     """
 
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     # status bit 1, 13, 24, 34, 47
 
-    if wrongstatus(d, 1, 3, 12):
+    if common.wrongstatus(d, 1, 3, 12):
         return False
 
-    if wrongstatus(d, 13, 14, 23):
+    if common.wrongstatus(d, 13, 14, 23):
         return False
 
-    if wrongstatus(d, 24, 25, 33):
+    if common.wrongstatus(d, 24, 25, 33):
         return False
 
-    if wrongstatus(d, 34, 35, 46):
+    if common.wrongstatus(d, 34, 35, 46):
         return False
 
-    if wrongstatus(d, 47, 49, 56):
+    if common.wrongstatus(d, 47, 49, 56):
         return False
 
     ias = ias53(msg)
@@ -68,13 +69,13 @@ def hdg53(msg):
     Returns:
         float: angle in degrees to true north (from 0 to 360)
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[0] == "0":
         return None
 
     sign = int(d[1])  # 1 -> west
-    value = bin2int(d[2:12])
+    value = common.bin2int(d[2:12])
 
     if sign:
         value = value - 1024
@@ -97,12 +98,12 @@ def ias53(msg):
     Returns:
         int: indicated arispeed in knots
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[12] == "0":
         return None
 
-    ias = bin2int(d[13:23])  # knots
+    ias = common.bin2int(d[13:23])  # knots
     return ias
 
 
@@ -115,12 +116,12 @@ def mach53(msg):
     Returns:
         float: MACH number
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[23] == "0":
         return None
 
-    mach = bin2int(d[24:33]) * 0.008
+    mach = common.bin2int(d[24:33]) * 0.008
     return round(mach, 3)
 
 
@@ -133,12 +134,12 @@ def tas53(msg):
     Returns:
         float: true airspeed in knots
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[33] == "0":
         return None
 
-    tas = bin2int(d[34:46]) * 0.5  # kts
+    tas = common.bin2int(d[34:46]) * 0.5  # kts
     return round(tas, 1)
 
 
@@ -151,13 +152,13 @@ def vr53(msg):
     Returns:
         int: vertical rate in feet/minutes
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[46] == "0":
         return None
 
     sign = int(d[47])  # 1 -> negative value, two's complement
-    value = bin2int(d[48:56])
+    value = common.bin2int(d[48:56])
 
     if value == 0 or value == 255:  # all zeros or all ones
         return 0
diff --git a/pyModeS/decoder/bds/bds60.py b/pyModeS/decoder/bds/bds60.py
index 75f2927..d9de28f 100644
--- a/pyModeS/decoder/bds/bds60.py
+++ b/pyModeS/decoder/bds/bds60.py
@@ -4,7 +4,8 @@
 # ------------------------------------------
 
 from __future__ import absolute_import, print_function, division
-from pyModeS.decoder.common import hex2bin, bin2int, data, allzeros, wrongstatus
+
+from pyModeS import common
 
 
 def is60(msg):
@@ -17,26 +18,26 @@ def is60(msg):
         bool: True or False
     """
 
-    if allzeros(msg):
+    if common.allzeros(msg):
         return False
 
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     # status bit 1, 13, 24, 35, 46
 
-    if wrongstatus(d, 1, 2, 12):
+    if common.wrongstatus(d, 1, 2, 12):
         return False
 
-    if wrongstatus(d, 13, 14, 23):
+    if common.wrongstatus(d, 13, 14, 23):
         return False
 
-    if wrongstatus(d, 24, 25, 34):
+    if common.wrongstatus(d, 24, 25, 34):
         return False
 
-    if wrongstatus(d, 35, 36, 45):
+    if common.wrongstatus(d, 35, 36, 45):
         return False
 
-    if wrongstatus(d, 46, 47, 56):
+    if common.wrongstatus(d, 46, 47, 56):
         return False
 
     ias = ias60(msg)
@@ -67,13 +68,13 @@ def hdg60(msg):
     Returns:
         float: heading in degrees to megnetic north (from 0 to 360)
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[0] == "0":
         return None
 
     sign = int(d[1])  # 1 -> west
-    value = bin2int(d[2:12])
+    value = common.bin2int(d[2:12])
 
     if sign:
         value = value - 1024
@@ -96,12 +97,12 @@ def ias60(msg):
     Returns:
         int: indicated airspeed in knots
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[12] == "0":
         return None
 
-    ias = bin2int(d[13:23])  # kts
+    ias = common.bin2int(d[13:23])  # kts
     return ias
 
 
@@ -114,12 +115,12 @@ def mach60(msg):
     Returns:
         float: MACH number
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[23] == "0":
         return None
 
-    mach = bin2int(d[24:34]) * 2.048 / 512.0
+    mach = common.bin2int(d[24:34]) * 2.048 / 512.0
     return round(mach, 3)
 
 
@@ -132,13 +133,13 @@ def vr60baro(msg):
     Returns:
         int: vertical rate in feet/minutes
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[34] == "0":
         return None
 
     sign = int(d[35])  # 1 -> negative value, two's complement
-    value = bin2int(d[36:45])
+    value = common.bin2int(d[36:45])
 
     if value == 0 or value == 511:  # all zeros or all ones
         return 0
@@ -158,13 +159,13 @@ def vr60ins(msg):
     Returns:
         int: vertical rate in feet/minutes
     """
-    d = hex2bin(data(msg))
+    d = common.hex2bin(common.data(msg))
 
     if d[45] == "0":
         return None
 
     sign = int(d[46])  # 1 -> negative value, two's complement
-    value = bin2int(d[47:56])
+    value = common.bin2int(d[47:56])
 
     if value == 0 or value == 511:  # all zeros or all ones
         return 0
diff --git a/pyModeS/decoder/c_common.pxd b/pyModeS/decoder/c_common.pxd
index e311ddf..fe8892e 100644
--- a/pyModeS/decoder/c_common.pxd
+++ b/pyModeS/decoder/c_common.pxd
@@ -19,5 +19,5 @@ cpdef int cprNL(double lat)
 cpdef str idcode(str msg)
 cpdef int altcode(str msg)
 
-cdef str data(str msg)
+cpdef str data(str msg)
 cpdef bint allzeros(str msg)
diff --git a/pyModeS/decoder/c_common.pyx b/pyModeS/decoder/c_common.pyx
index 2c76cf7..efb489b 100644
--- a/pyModeS/decoder/c_common.pyx
+++ b/pyModeS/decoder/c_common.pyx
@@ -391,7 +391,7 @@ cdef int gray2int(str graystr):
     return num
 
 
-cdef str data(str msg):
+cpdef str data(str msg):
     """Return the data frame in the message, bytes 9 to 22."""
     return msg[8:-6]
 
diff --git a/pyModeS/decoder/surv.py b/pyModeS/decoder/surv.py
index 91b8c38..746f47f 100644
--- a/pyModeS/decoder/surv.py
+++ b/pyModeS/decoder/surv.py
@@ -3,6 +3,3 @@ Warpper for short roll call surveillance replies DF=4/5
 
 [To be implemented]
 """
-
-from __future__ import absolute_import, print_function, division
-from pyModeS.decoder import common
diff --git a/pyModeS/decoder/uplink.py b/pyModeS/decoder/uplink.py
index cf1f109..586ee56 100644
--- a/pyModeS/decoder/uplink.py
+++ b/pyModeS/decoder/uplink.py
@@ -1,21 +1,22 @@
-from pyModeS.decoder import common
+from pyModeS import common
+
 
 def uplink_icao(msg):
-	"""Calculate the ICAO address from a Mode-S interrogation (uplink message)"""
-	p_gen = 0xfffa0480 << ((len(msg)-14)*4)
-	data = int(msg[:-6],16)
-	PA = int(msg[-6:],16)
-	ad = 0
-	topbit = 0b1 << (len(msg)*4-25)
-	for j in range(0,len(msg)*4,1):
-		if (data & topbit):
-			data^=p_gen
-		data = (data << 1) + ((PA >> 23) & 1)
-		PA = PA << 1
-		if (j>(len(msg)*4-26)):
-			ad = ad + ((data >> (len(msg)*4-25)) & 1)
-			ad = ad << 1
-	return "%06X" % (ad >> 2)
+    """Calculate the ICAO address from a Mode-S interrogation (uplink message)"""
+    p_gen = 0xFFFA0480 << ((len(msg) - 14) * 4)
+    data = int(msg[:-6], 16)
+    PA = int(msg[-6:], 16)
+    ad = 0
+    topbit = 0b1 << (len(msg) * 4 - 25)
+    for j in range(0, len(msg) * 4, 1):
+        if data & topbit:
+            data ^= p_gen
+        data = (data << 1) + ((PA >> 23) & 1)
+        PA = PA << 1
+        if j > (len(msg) * 4 - 26):
+            ad = ad + ((data >> (len(msg) * 4 - 25)) & 1)
+            ad = ad << 1
+    return "%06X" % (ad >> 2)
 
 
 def uf(msg):