[aprssig] Advice requested please

Georg Lukas georg at op-co.de
Sun May 5 09:55:35 CDT 2013


Hi Chris,

* Chris Moulding <chrism at crosscountrywireless.net> [2013-05-05 12:19]:
> Recently I've been developing a Bluetooth version of the APRS TNC
> Digi Tracker. I've also written an Android app which receives the
> APRS traffic received by the Digi Tracker sent over the Bluetooth
> link. The app can also igate the traffic to the APRS-IS over wi-fi
> or 3G.

I'm not familiar with the exact TNC type, but setting it to KISS mode
instead of TNC2 text would allow you to check the CRC checksum of
incoming packets, thus verifying their integrity.

Also, may I suggest that you have a look at the APRSdroid app
<http://aprsdroid.org> I am developing? It already supports several
types of TNC connections and APRS-IS, it just needs some refactoring
to allow i-gating.

There is also javAPRSlib by John AB0OO to parse and generate APRS
packets, and the great AFSK demodulator called javAX25lib by Sivan
4X6IZ, so there is no need to reinvent the wheel! :)

> There is however a problem. When the distance between the Digi
> Tracker and Android phone gets too high the Bluetooth link starts
> losing the first few characters from some packets before the
> Bluetooth link fails. This could allow incorrect packets to be sent
> to the APRS-IS usually with errors in the station callsign.

This looks like a bug in the Bluetooth stack of one of your devices. In
theory, such things should not happen at all... maybe you can "fix" it
by upgrading your Android / test with another device...

I've had really bad experience with the default ROMs on many Android
devices, from hanging my app to rebooting the OS.


73 from Germany,

Georg DO1GL
-- 
APRSdroid - Open Source APRS Client for Android ++ http://aprsdroid.org/m
     ++ https://market.android.com/details?id=org.aprsdroid.app ++
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