[Tutor] Consistant Overhead Byte Stuffing (COBS) algorithm help

Michael Cotherman mjcother at yahoo.com
Tue Oct 4 21:26:16 CEST 2005


A little more info is below:


With miniterm modified to output hex to the screen,
here is the data coming in unformatted. (note zero
bytes delimit end of packet):

c:\Python23>python miniterm1.1a.py
--- Miniterm --- type ESC to quit
0002860104DB203F01000002860504CB1A7401000002860504CB1B7401000002860504CB1B740100
0002860504CB1B7401000002860504CB1B7401000002860504CB1B7401000002860504CB1B740100
0002860504CB1B7401000002860504CB1B7401000002860504CB1B740100



Here I have formatted it(one line equals a packet,
currently about every 30 seconds):

c:\Python23>python miniterm1.1a.py
--- Miniterm --- type ESC to quit
00-02-86-05-04-CB-1B-74-01-00
00-02-86-05-04-CB-1B-74-01-00
00-02-86-01-04-DB-20-3E-01-00
00-02-86-05-04-CB-1B-74-01-00
00-02-86-05-04-CB-1B-74-01-00
00-02-86-05-04-CB-1B-74-01-00
00-02-86-05-04-CB-1B-74-01-00
00-02-86-05-04-CB-1B-74-01-00
00-02-86-05-04-CB-1B-74-01-00
00-02-86-05-04-CB-1B-74-01-00
00-02-86-05-04-CB-1B-74-01-00
00-02-86-05-04-CB-1B-74-01-00



here is what the data will look like after COBS
decoding (the zero bytes are real data):
86-00-04-CB-1B-74-00
86-00-04-CB-1B-74-00
86-00-04-CB-1B-74-00
86-00-04-CB-1B-74-00
86-00-04-CB-1B-74-00
86-00-04-CB-1B-74-00
86-00-04-CB-1B-74-00


For those who are curious as to what I am doing, here
is what telemetry is in the packet:
packe type        = 0x86
Device ID         = 0x0004
Payload:
----Batt Volt.    = 0xCB
----Pot Volt.     = 0x1B
----Temp Volt.    = 0x74
----sw 1          = 0
----sw 2          = 0
----sw 3          = 0
----sw 4          = 0
----Btn 1         = 0
----Btn 2         = 0
----Yel LED       = 0
----Red LED       = 0


Thanks,
mike



	
		
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