Wednesday, October 23, 2013

Bluetooth KISS TNC for Android devices $50 with Li-Ion Battery (MobilinkD)

This looks pretty interesting.  It's a nicely done bit of integration, to provide a hardware TNC for APRS operation at a reasonable price as long as you have an Android phone or tablet handy.

There are several HTs with APRS built-in. I own a Yaesu VX-8DR.  However the user interface on the radio is very limited and there is no direct access to the TNC.  The APRS on my VX-8DR isn't all that useful to me because the GPS is external. The GPS from Yaesu is very expensive and reportedly doesn't perform very well: poor reception, high power drain.

A cheap, Chinese HT could be combined with this to make a nice functional APRS unit that is still pretty portable.  See my other posts about APRSdroid.

  • Small battery operated TNC for attaching to an HT in a backpack style setup. 
  • Connect to Android via Bluetooth serial protocol, so no cable needed to the phone or tablet.   Only an audio cable is needed to connect the TNC to the HT.
  • Designed to work with APRSdroid, a great free or paid APRS application for Android.
  • Has a 1,200 mAh Li-Ion battery for 48 hours of operation, includes USB port and battery management chip to charge the battery.
  • Open source design.   Code and schematics are available.
  • Easily hackable, microcontroller is Atmega 328 same as Arduino, An Arduino can be used to program it if you are building it from a bare atmega328
  • Based on an AVR/Arduino TNC design that uses a real time OS (BeRTOS) by KI4MCW.  This has been on my list to build and experiment with for a while.
  • Could reuse the hardware for other projects/digital audio protocols. The board is basically a battery powered Arduino with a bluetooth serial interface, and rudimentary audio input/output.

Mobilinkd's site:

Other side notes of possible interest

  • Android Only - This will not work on iOS, because Apple doesn't have (or won't allow) Bluetooth Serial Protocol access from iOS apps.  Openness is the primary reason I have an Android phone instead of going with the flow and having a locked down iOS device like everyone else.
  • The Yaesu VX-8DR GPS unit requires buying not only the GPS module but either a bracket to attach it to the top of the radio or the external waterproof mic unit. The external mic is also pretty overpriced. The connectors for both the mic, and the GPS are proprietary.
  • The Yaesu VX-8GR had the GPS built-in and allowed getting the waypoints from the serial connector. However it has been discontinued as of sometime in 2013. It was going for a reasonable price, approximate $350 before it was discontinued.
  • I've considered building a GPS for the VX-8DR using Adafruit's Ultimate GPS module which sounds pretty cool. However, the GPS parser in the VX-8 will only handle GPS sentences with the same padding as the Yaesu unit. It's possible that the Adafruit unit, which has an onboard microcontroller could be adapted to make it VX-8D friendly, but it's not clear if that is achievable, at least without a ton of effort.