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I have a usb stick that communicates with a medical device. I am attempting to decode the communication. I have figured out the basic radio parameters (916.5MHz, ook, bit rate, preamble, sync words), but there is still some radio related parameter I haven't figured out yet.

I can give the USB stick different destination device ids, and can see segments of the short (~12bytes) packet change. In fact, for each character of the 6-digit device id, I see 6 bits change in the packet, with a consistent mapping as follows:

"010101" => "0",
"110001" => "1",
"110010" => "2",
"100011" => "3",
"110100" => "4",
"100101" => "5",
"100110" => "6",
"010110" => "7",
"011010" => "8",
"011001" => "9"

So device id 123456 is encoded as "110001110010100011110100100101100110".

There are some other 6-bit sequences I see in the data as well, like:

001011 => ?
001101 => ?
101010 => ?
101100 => ?
011100 => ?

The second bit in each code to be a parity bit for the remaining 5 bits. The first bit seems special in some way as well, but I haven't figured it out.

Any ideas?

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    $\begingroup$ This question appears to be off-topic because it is not about amateur radio. $\endgroup$ – user Dec 23 '13 at 11:57
  • $\begingroup$ Some kind of balanced 6 bit error correcting codes with Hamming weight of 3? Might also be pair of matched 3 bit symbols as if first 3 bits have two ones, must the last three bits have just one one. Three are no 000 or 111 in the beginning or end. $\endgroup$ – jkj Dec 28 '13 at 13:13

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