Communication of the Past

[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

[Yharaskrik]

http://en.wikipedia.org/wiki/RS-232

[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?

[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]

[Redford]

Thanks!

[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.