[aprssig] Advice requested please

Gregg Wonderly gregg at wonderly.org
Mon May 6 09:53:31 CDT 2013


In computer networking, this is a layer-3 problem.  Layer 1 is bluetooth.  Layer 2 is the serial stream.  So you really need to consider how to provide a valid end-to-end stream across that network so that your application works as expected.  Only complete packets should traverse the network, because your application depends on that data being complete/correct.

If you were going to add the ability to send command/control between the android app and the Digi-Tracker, then you would be introducing a layer-4, application protocol.  For example, if you had a configuration file on the digi tracker that you wanted to update from the android app, then you'd need to introduce a layer-4 protocol that would allow you to designate the difference between data destined for the TNC (if it was able to transmit packets) and data that would overwrite the configuration.

If you will think about your design from this perspective, it will help you separate concerns and create great software that does exactly what you need it to do.

Gregg Wonderly
W5GGW

On May 5, 2013, at 12:40 PM, Chris Moulding <chrism at crosscountrywireless.net> wrote:

> Thanks for all the suggestions, I'll consider all of them.
> 
> The Digi Tracker outputs TNC2 packets so the Android program at present is a simple Bluetooth serial connection with a TCP/IP connection for igating to the APRS-IS.
> 
> I've also found a way of reliably testing a poor Bluetooth connection so I can test all the possible solutions.
> 
> Regards,
> 
> Chris, G4HYG
> 
> 
> 
> --
> Chris Moulding
> Cross Country Wireless
> 7 Thirlmere Grove, Bolton, Lancs, BL4 0QB, UK
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