I designed a PCB for a programming box (based on OlliW’s original schematic) for the Assan GA250 gyro flashed with OlliW’s custom firmware (see my original post about flashing your gyro here). The programming box hooks up to your gyro and enables you to tune the parameters on the field.
The design is really simple, it basically has an ATMega8, four buttons, 16×2 HD44780 compatible LCD and some auxiliary stuff. The PCB also has an ISP connector for programming the AVR.
If you want to make one yourself, you need a piece of two-sided PCB but you only need to etch one side. The top layer is just a ground layer so you do not have to etch it, just make sure none of the component legs DO NOT touch the ground layer unless they are supposed to be grounded (all the pins which have a top layer track connected are supposed to be grounded). The best way to do this is to drill all the through holes, and then drill the holes from the top with a larger drill bit (not through, just to remove the ground layer so that the component pin does not touch it).
The pin header pin that is grounded is a bit tricky to solder to the top layer, but a good trick for that is to take one thin strand of wire from some wire, solder it to the pin header pin, then solder the pin header and solder the strand to the top layer. You also need to solder a jump wire from the ISP reset pin to the reset pin on the ATMega. The ISP connector has the same pin out as the usual 6-pin AVR ISP connector (just make sure you attach the cable the right way around!).
Make sure your LCD fits my layout, the 16×2 LCDs are NOT standardized in size (though most are pretty close in size/measurements).
You can get a zip which contains all the necessary files (KiCAD schematic/layout files, .hex firmware file and .pdf which contains the PCB layout you can use to etch your PCB) from here: Programming box files