[aprssig] rino decoding.

[Wes Johnston]

I have started to dig into the rino data format on air.

I connected the DISC out of a 9k6 ready radio and hooked it to my PC's 
line input.  I recorded some 44.1khz 16 bit wav files of sending my 
posit and also of sending an APRS* query.

Analysis of these wav files shows me that I end up with a slightly 
different bit rate than Bob B shows on his web site.  I measured 1.627mS 
between bits or 614 bps.

I also noticed in three of the four recordings I made that the time 
between unkeying an initial pulse of one bit when I unkey the mic and 
the center of the first data bit is about 286.6mS (175 bit timings) .  I 
am wondering if the first databit at the release of PTT is a synch.  My 
four samples yeilded the following times between that first "synch" bit 
and the first data bit of 286.62ms,340.45ms,282.13ms and 280.50ms.  The 
340ms is obviously a fluke, but the radio did it... Perhaps the modem in 
the RINO doing the receiving looks for 1 bit, then 175 bits of silence, 
and that flags the start of a packet?

Bob, if you read this, can you tell me with any certainty that the data 
is exactly 600bps or 614bps?  It is entirely possible my sound card is a 
little off.  2.33% seems a little much though....  I should have a hand 
made 8 bit wav file tomorrow of the APRS* query.

I have a few goals:

1)make an 8 bit wav file that contains cleaned up sounds... no noise, 
just the bits.

2)build a PIC processor modem that can read the garmin format on air 
from my 9600 capable radio and spit out a standard aprs object packet 
suitable to shoot straight into a KISS TNC.

3)Find out if audio coupling can be used or if direct coupling to the 
DISC is needed.  If this is true, then I could (in theory) play a wave 
file by holding my RINO unit near a speaker and poll other rino units 
without having to push the Poll menu button.

I have posted the wav files at http://www.kd4rdb.com/aprs/rino/ if 
anyone wants to play with them.

Wes