The first programmer prototype is designed! You can see the layout here.
It's a fairly straightforward design, with an Arm Cortex microcontroller with USB doing the heavy lifting. The whole programmer board can be plugged into a breadboard for easy testing of new designs.
A capacitative voltage doubler and zener shunt regulator generates the 7.5V needed to program the greenpak, while a couple of analog switches prevent the programming signals from reaching the breadboarded device.
Here's the schematic in all its glory:
I'm holding off producing any samples until we've got a reasonable design and attachment method for the programming clip/socket discussed in the previous post.