This board took about 10 minutes of milling and tool changing time, plus another 5 minutes for setup and touching off. Compared to earlier boards I've shown, the main change is to use a 1/32" precisebits diamond-cut router bit instead of the 1/16" 2-flute mill I usually use for milling large holes and cutting out the board from the larger copper-clad blank. This bit turns the board substrate into fine dust, a few clumps of which can be seen in the board scan. I ran it at a very conservative 4IPM this time around, but I think I could run it faster.
If you look at the full-size circuit board scan, you'll notice three main problems: the "circular" pads of the HD15 connector are pretty irregular; the octagonal pads are lopsided; and drills are often off-center in their pad. I attribute all these things to backlash. Besides re-measuring and entering the values for backlash on X and Y, I don't think there's anything easy to do about this. Anyway, the results are tolerable.(another problem is the small uncleared areas of copper are more of a trade-off than a problem: I could do more passes, or do a pass with an end-mill, at the expense of increased milling time)
Its purpose is to turn 14 GPIOs on the A2 connector of the S3BOARD FPGA into a 12-bit (4096-color) VGA interface. Projects I might make with this would be a retro-style gaming system, emulation of classic home systems or classic arcade systems. Or maybe I'll work on turning the FPGA-based logic analyzer into a device that doesn't need a PC to operate--just a mouse and a VGA monitor.(Or maybe I'll just display that test pattern and then let this board find
its way to the back of the junk bin)
(originally posted on the AXIS blog)