I did some tests of the 555 timer based temp feedback. The resolution at operating temperature was poor ~7 degrees. The resolution at room temperature was a lot worse ~30 degrees. The refresh rate was also poor. Seems the sensor chip was outputting at 1hz. That would be fine for fan speed feedback, but a little low for temperature feedback I think.

CYMK is also on hold. I'm missing 2 steppers, 4 stepper driver ICs, and most importantly I came up 2 outputs short on my parallel port interface. After extensive research about various other IO hacks, including being able to get the needed IO by bit banging the serial port and level shifting the output from Rs232 back to TTL, I decided it wasn't worth the work.

I've broken down and ordered a Beaglebone black. That will give me all the IO I will ever need, good floating point performance (as this is a delta, every move involves some floating point calculations) and no more bit banging as I have 2 dedicated 200Mhz hardware PRU's, for $45.

From the spec sheet and browsing around, I've determined I should run it off the ATX standby line, and enable the ATX power after it is powered via a GPIO. This eliminates the issue I was *going* to have where if I just powered it all off the ATX and tied power-on, my sensors/parallel port card would have driven GPIO pins before the processor was ready for it, and would have destroyed it.

Now where is that HDMI to DVI cable...