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Communication of the Past
Posted: Thu Jun 12, 2014 1:29 pm
by Redford
I've solved this task searching in English dict for 4 letter words with specific distance between letters (like word[1] == word[2]), so I still don't know what's the used protocol/encoding. Does anyone of you know what it was?
Thanks,
Redford
Posted: Fri Jun 13, 2014 7:10 am
by Yharaskrik
Posted: Sat Jun 14, 2014 11:02 pm
by Redford
Are you sure that's RS-232? RS-232 transports just raw bits:
https://en.wikipedia.org/wiki/RS-232#me ... _trace.svg
That standard doesn't say anything about transported data (e.g. bit order, encoding etc), it could be any RS-something.
I rather asked about the protocol in which those letters are encoded+transported
Quick reminder:
In this task bits were packed by four and a '1' was prepended to each group ('.' == '0'):
Code: Select all
1...1
1..1.
1....
1..1.
1....
1..1.
111.1
1..1.
<bit 1><4 bits of data>
After concatenation you get:
Code: Select all
...1..1.
......1.
......1.
11.1..1.
After reversing bit order we get some numbers, which aren't ASCII, but some strange letter encoding (or maybe I decoded it wrongly?)
What's that encoding?
Posted: Mon Jun 16, 2014 6:52 am
by Yharaskrik
If you look at the picture you posted, you see that there are 8 bits of data with LSB first between START and STOP. So the solution is:
Code: Select all
Original: 0 11100110 1 0 11110110 1 0 11110110 1 0 00100110 1 111
MSB first: S 01100111 S S 01101111 S S 01101111 S S 01100100 S I
t 0x67=g t t 0x6f=o t t 0x6f=o t t 0x64=d t d
a o a o a o a o l
r p r p r p r p e
t t t t
-> "good"
[/code]
Posted: Mon Jun 16, 2014 9:23 am
by Redford
Thanks!
Years...
Posted: Tue Mar 14, 2023 2:32 pm
by yes-man
This one took me a while. I always assumed it was some old-ish Layer-1 protocol, but somehow I never ended up at RS-232. Except for today.
Then it was just a matter of messing around for a bit. Does every letter have a Start-Stop envelop? Ahhhh, LSB first... And well, there it was.
