[Commit-gnuradio] r3617 - gnuradio/branches/developers/eb/digital-wip/gnuradio-core/src/python/gnuradio

[eb]

Author: eb
Date: 2006-09-22 12:14:03 -0600 (Fri, 22 Sep 2006)
New Revision: 3617

Modified:
   
gnuradio/branches/developers/eb/digital-wip/gnuradio-core/src/python/gnuradio/packet_utils.py
Log:
added preamble to packet header

Modified: 
gnuradio/branches/developers/eb/digital-wip/gnuradio-core/src/python/gnuradio/packet_utils.py
===================================================================
--- 
gnuradio/branches/developers/eb/digital-wip/gnuradio-core/src/python/gnuradio/packet_utils.py
       2006-09-22 18:04:26 UTC (rev 3616)
+++ 
gnuradio/branches/developers/eb/digital-wip/gnuradio-core/src/python/gnuradio/packet_utils.py
       2006-09-22 18:14:03 UTC (rev 3617)
@@ -71,8 +71,9 @@
 
 default_access_code = \
   conv_packed_binary_string_to_1_0_string('\xAC\xDD\xA4\xE2\xF2\x8C\x20\xFC')
+preamble = \
+  conv_packed_binary_string_to_1_0_string('\xAA\xAA\xAA\xAB')
 
-
 def is_1_0_string(s):
     if not isinstance(s, str):
         return False
@@ -97,7 +98,8 @@
 def make_header(payload_len):
     return struct.pack('!HH', payload_len, payload_len)
 
-def make_packet(payload, samples_per_symbol, bits_per_symbol, 
access_code=default_access_code, pad_for_usrp=True):
+def make_packet(payload, samples_per_symbol, bits_per_symbol,
+                access_code=default_access_code, pad_for_usrp=True):
     """
     Build a packet, given access code and payload.
 
@@ -115,6 +117,7 @@
         raise ValueError, "access_code must be a string containing only 0's 
and 1's (%r)" % (access_code,)
 
     (packed_access_code, padded) = 
conv_1_0_string_to_packed_binary_string(access_code)
+    (packed_preamble, ignore) = 
conv_1_0_string_to_packed_binary_string(preamble)
     
     payload_with_crc = gru.gen_and_append_crc32(payload)
     #print "outbound crc =", string_to_hex_list(payload_with_crc[-4:])
@@ -124,7 +127,7 @@
     if L > MAXLEN:
         raise ValueError, "len(payload) must be in [0, %d]" % (MAXLEN,)
 
-    pkt = ''.join((packed_access_code, make_header(L), 
whiten(payload_with_crc), '\x55'))
+    pkt = ''.join((packed_preamble, packed_access_code, make_header(L), 
whiten(payload_with_crc), '\x55'))
     if pad_for_usrp:
         pkt = pkt + (_npadding_bytes(len(pkt), samples_per_symbol, 
bits_per_symbol) * '\x55')