These are preliminary sources and CAD files from the Freifunk-Open-MPP-Tracker project.
This is a Open-Source and Open-Hardware project under General Public License v2 and Creative Commons - Attribution - ShareAlike 3.0. For more information, check out the LICENSE file.
A QUICK OVERVIEW OF THE DIRECTORIES:
Contains a XML configuration file to program the fuses of the AVR. I am using the AVR dragon board and AVR-Burn-O-Mat software to program the fuses.
SCHEMATIC AND BOARD
Electronic CAD files and component libraries, made with KiCAD. KiCAD is a free and open ECAD tool. Due to the intend to provide a open hardware and open software project for DIY home-brewers, I have decided to use a free and open source ECAD software tool, too. It is my first project with KiCAD, though.
AVR-GCC source and Makefile.
SOME NOTES ABOUT THIS DESIGN
Basically this hardware has two building blocks: The MPP controller section and the buck converter.
At the moment, the buck converter section is based on the el cheapo and low-fi MC33063 controller chip. It can easily be replaced by a faster and more fancy switch converter IC to construct a more powerful and slightly more efficient buck converter section. However, with the external powerful P-MOS switches, the efficiency was already around 94% with the first prototype (measured at 2 Ampere output current).
One reason to replace the MC33063 might be noise. Under low load, the MC33063 will skip pulses of the PWM, so the switching frequency becomes audible.