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[aprssig] Tracker3 OT3m

Scott Miller scott at opentrac.org
Thu Jan 5 20:14:46 UTC 2012

We *finally* got the finished cases for the new OT3m boards in late 
yesterday.  I've posted some pictures to Facebook in case anyone wants 
to check it out:


The first few units are going to ship today.  It'll take at least 2 
weeks to catch up with orders in the queue.

Right now the T3 looks and acts very much like the T2.  But where the T2 
has an 8-bit CPU running at 7.37 MHz, the T3 has a 32-bit CPU running at 
48 MHz.  It also has considerably more code space and RAM, so there's a 
lot more room for new features.

All of the demodulation is done in software, and performance is on par 
with the MX614 demodulator used on the OT2m in my testing.  Hopefully 
I'll be able to add 9600 baud support before long.

USB support is identical to the OpenTracker USB - the USB port shows up 
as a COM port (or tty) for configuration or KISS use, and the two 
regular serial ports continue to function as usual.  Unlike the OTUSB 
(or any other previous tracker, really) it's able to update the entire 
firmware, including the USB stack and bootloader, even when it's being 
updated over USB.

The pluggable screw terminal block on the front makes it easy to connect 
analog telemetry inputs.  The four analog inputs are set up for 0-20v 
and report in 1/10 volt increments, so the analog values are easily 

Internally, component count is reduced and assembly is simplified.  The 
enclosure is a cleaner, simpler 2-piece design, and there are a couple 
of #4-40 standoffs on the bottom that can be used to attach the unit to 
a mounting bracket.

The only downside so far is power consumption - it's up to about 50 mA 
from 20 mA on the OT2m, but this should fall with future firmware updates.

I also added a spot for a PS/2 keyboard connector on the latest PCB. 
There's no hole for it in the case, but it does work - you can plug in a 
keyboard and type commands in the blind.

There's some more information on the wiki here:


Any pending OT2m orders will be filled with OT3ms unless customers 
request otherwise.  I'll put up a new product listing once we've caught 
up with pending orders.  The price will be the same as the OT2m at $95.


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