I finally received my PCB's today. The DirtyPCB service thoughtfully bundled all three board types I ordered (two for this project, one for the Rubidium Oscillator controller project). The board quality seems good. A slight registration error in the silkscreen on one of the boards, but really nothing worth complaining about. It's been a while since I've assembled HASL'd boards - I got spoiled by the ENIG finish that OSHpark provides.

I put together both boards in less than an hour, and other than having to diddle a resistor value in each of the 48V and 9V voltage comparator circuits, no issues. I think I simulated the comparator circuit with an incorrect value of reference voltage (derived from the 5V power LED) so I had to adjust the divider input R to achieve the correct threshold voltages (40V and 8V). I'll have to look into this to be sure.

I threw together a quick loopback test setup with the two DerbyLink boards, a 100-foot CAT5 patch cord, a 48V supply, and a 30-ohm load (300mA at 9V) to simulate the draw of the MicroWizard finish line. It's presently undergoing 'burn-in' in my basement lab. I found a nice COM port loopback test program, so I'll let that run overnight checking the USB -> RS422 -> RS232 -> RS232 -> RS422 -> USB link at bitrates between 2400...115200 bps.