Drop in firmware for TinyTrak3(c) or FreeTrak
Send serial data using 1200 baud AX.25 packet radio
The Byonics TinyTrak3(c)
One of the most lightweight packet encoders in use for high altitude balloon experiments.
Now serial data to packet firmware is available to make putting your micro projects on the air a snap.
Data Trak features:
Simple serial configuration menu.
Sends data strings up to 150 bytes.
9600 baud serial data input.
1200 baud AX.25 packet out.
Busy channel holdoff.

Successful 1st flight on November 13, 2004 aboard NSTAR 04G to over 90,000 feet!! A custom version of DataTrak substituted for a KPC3 TNC saving about 8 ounces of payload weight.
Here's a sample of the NSTAR 04G flight computer telemetry sent by DataTrak.
N9XTN-11>GPSPO:/151544h4117.44N/09512.68WO080/030/A=055181 3D04Sats 39FPM C28 NSTAR04G SmplxRptr446.3
N9XTN-11>GPSPO:T054 Baro 85 mb 1102 logs 73%RH
N9XTN-11>GPSPO:>NSTAR04G Smplx Rptr 446.30 Backup APRS 144.39

DataTrak has since flown aboard all of NSTAR's near space missions.

It's simple to change your callsign and path parameters.
Powering up the TinyTrak with J5 jumpered puts it in config mode.
The interactive screens let you set the callsigns, up to 3 digis, TXD and text echo.
The results are stored in EEPROM memory.
Cycle the power with the jumper off for TX mode.
Screenshot of DataTrak configuration.
Revision history:
Ver 3.0 - 1st beta release 11-5-04
Ver 3.1 - fixed CD indicate 11-20-04
Ver 1.1 - Ported to FreeTrak 11-26-08

To use this free software you'll need a Microchip PIC 16F628A similar the one pictured above. You'll also need a programmer to install this software into the PIC like the $35 model pictured above from Microchip.

TinyTrak Tricks & Tips

PDF schematic
I had trouble with ground loop noise from my GPS power adaptor.
This opto isolator circuit separated the two electrically and solved the problem.
A small jumper from the 5v rail to DB9 pin #4 was the only internal mod.
Another unused pin (like #9) may be a better choice.

When building your TinyTrak, try replacing the 78L05 (U2) with a low drop out voltage regulator like the Micrel MIC2950.
DigiKey is one good source.
This is important, particularly if your using a battery for power. The 2950 is much more efficient and will continue to work even when the battery wears down to 5 volts or less.

Questions - Ask Mike

This page last updated 4-12-09

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