After coming up with some scripts to generate thousands of 200-byte
files and attempt to transfer them over a GMSK link, I isolated 5 of
‘files’ that cause the packet to be dropped (when the MTU is big enough
hold the entire 200 bytes- which should be all the time)- most likely
repeated zeros or ones that cause a loss of sync. Upon debugging the
after the whitener, it does appear that there are instances of around
12-zeros in the packets that don’t work.
It seems that a reasonably simple solution would be to replace or
the whitener with an 8b/10b encoding (per Widmer/Franaszek’s
which also would allow for a beginning and end of packet comma symbol
synchronization. The 8b/10b could replace the whitener completely, but I
read that passing it through the whitener and then the 8b/10b yields
spectral properties/dc balance.
I found dozens of Verilog/VHDL implementations by googling, but none in
software. I computed some tables and was part way into making some code
am at a couple of question marks that need to be answered.
- If I do somehow finish this (I’m not that great at Python just yet,
though am very familiar with other languages- so I can definitely finish
with the help of google), would this be something that would be
the tree (eg- do Matt/Eric/Johnathan, etc think this is the appropriate
- if (1), what is the bit and byte order over the wire for GMSK so that
can make sure I formulate the characters/packets in the right order.
- if (1), someone more familiar could probably implement this in
perhaps a couple of hours, whereas it’ll take me the better part of a
two- is anyone interested in helping me reduce the number of question
and think through doing this correctly?
Another viable option might be applying the TMDS method (XOR/XNORing)
creatively to this medium. The way I read it, the clock signal is only
frequency reference so I don’t see a reason why we cant use TMDS on a
clock-less medium if we don’t care about blanking periods, etc.
Please let me know if I’m off my rocker or if I’m pointing in the right
I look forward to your thoughts/comments.
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