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From George Smart's Wiki
See APRS for more general APRS stuff.
The board needs some very slight modifications, since the mounting holes are a little too close to the LEDs and other components in places. However, if you aren't too bothered by that, you can *** ORDER THE PCBS HERE *** The supplier is making my boards, but you deal with them directly. It saves messing around with the Gerber files below. You can give some of the spare boards to friends, or do a group-buy deal!
All files are here, but no explanatory text. This article will be written when I have some time. There's enough information to make the boards up, parts and placement, and links here to source code, but there's no "guide" as such.
I'm considering making this as a kit, since I've gone to the effort of having boards made. I think around £25 should cover costs. Feel free to make it yourself if you like. Masks and Gerbers below if you would prefer to make your own.
There is no "instruction" manual with this project at present, just the silk screen and schematic.
The aprstracker firmware version 0.12 (supporting 9600 baud GPS) by PE1ICQ and PE1RXQ can be downloaded here: aprstracker-0.12.tar.gz. It is not on the author's site, since there are bugs with the altitude code. However, the code is still useful for 9600 baud GPS. Use version 0.11 if you want altitude.
Using TTL GPSes
As GPS receivers are moving on to USB and Bluetooth, they become increasingly more expensive. The tracker, as with pretty much all trackers, uses RS232 input. Many of the cheap GPS receivers on eBay such as the VK16HX/VK16U6 receivers have TTL output for direct connection into Arduinos and other hobbiest projects. To make these compatible with the tracker, one needs to invert the TTL data (i.e., 1 becomes 0, and 0 becomes 1). This is because traditionally a MAX232 would be used.
Although a MAX232 is the right part to use, a simple transistor inverter will suffice, and I have used one on several occasions. The very poor hand drawn sketch was put up in a rush to aid with the explanation: