Hi Mike, Thanks for the reply while we still have time to fix things and stay on schedule.
Do you think it would be feasible to implement Mobitex in software on a µC, given a transceiver in transparent mode (will modulate and send any bits it receives on serial, and demodulate/receive any RF it receives)? We already have one dedicated to comms, and all other algorithms take place on a separate processor. I ask because at this point, it would be easier to change the software than the hardware (software has no mass or volume). I'd say Block formatting, CRC and bit & Frame Sync would be easy enough (everything's a multiple of a byte) because they're completely described, but the interleaving and scrambling aren't which makes things much harder. -Nate KC2SVI On Fri, Apr 9, 2010 at 4:03 AM, Mike Rupprecht <[email protected]>wrote: > Hi Nate, > > Sorry for the long delay.... > > MixW doesn't support GMSK. You mix that with MFSK. > > BeeSat has two CMX909B modems (CML) onboard. The data is sent in the > MOBITEX > format, not AX.25 ! > See here for more information about Mobitex: > http://en.wikipedia.org/wiki/Mobitex > > The CMX909B is a half-duplex Gaussian Minimum Shift Keyed (GMSK) BT = 0.3 > modem data pump with on-chip packet data handling. GMSK modulation > optimises > the data throughput for a given bandwidth RF channel and the on-chip packet > data handling relieves the host µC of regular processing tasks, such as > maintaining Bit and Frame Synchronisation, Block Formatting, CRC and FEC > Error Processing, Data Interleaving and Scrambling. > > 73, Mike > DK3WN > > > > > > > > -----Ursprüngliche Nachricht----- > Von: [email protected] [mailto:[email protected]] Im > Auftrag von Tom Azlin N4ZPT > Gesendet: Freitag, 9. April 2010 00:28 > An: AMSAT-BB > Betreff: [amsat-bb] Re: BeeSat at 4800 GMSK > > Hi Nate, > > I was not aware MixW had MSK in it but still identical to GMSK. Perhaps > you are thinking of MFSK? In the MixW program there is MSFK16, a > multitone frequency shift signal, is supported, but not Minimum Shift > Keying or Gaussian Minimum Shift Keying signals. And also FSK, aka RTTY. > > There is work going on to make a sound card 4800 bps 0.5 time-bandwidth > product GMSK soundcard modems for use in GMSK DV adapters to use with > D-STAR radios. Perhaps that could be adapted for your purpose? > > http://www.qsl.net/kb9mwr/projects/voip/dstar/G4KLX.html seems to > describe some of the work. > > http://groups.yahoo.com/group/dstar_development/ and > ttp://groups.yahoo.com/group/pcrepeatercontroller/ are where I see the > discussion underway. > > Separate discussion is using an external sound card interface like the > Rigblaster, to connect a computer and radio. > > 73, Tom n4zpt > > Nathaniel S. Parsons wrote: > > Can I assume MSK=GMSK? I thought they were different, but they are the > same, > > and since MixW has MSK, and I could use that with a Rigblaster, etc, > right? > > > > -Nate > _______________________________________________ > Sent via [email protected]. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > > _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
