2019-01-04

Long story made short:  more failure.  One very basic failure was mixing up SSOP footprints with TSSOP footprints.  I have a laundry list of excuses for screwing it up, but at the end of the day a lesson has been learned that should have been learned many times over in the past – don’t try to hand-wave things away.  Experience is the name we give to our failures, I suppose.

A more subtle failure was discovered when I hooked up communication (RS-232) between the IO board and the VPSB (Vic’s Power and Serial Board).  The IO board would not power down.  Turns out there was enough leakage between the two RS-232 drivers to power up the IO board.

Of course the first question is: how is the board a capacitive load too large for a power supply, yet is happily driven by an RS-232 driver?!  Good question.  Moving on.

My scheme of switching the ground proved to be a terrible idea.  Current, apparently like love, will find a way.  As long as there is some potential difference, the stupid electrons will find a way.  For my ‘not shit’ version of the design I will be using a Linear LTC7004 high side driver.

This is another failure that pissed me off beyond words because I hand-waved this decision away as well.  My gut (and the literature!) said that switching the ground was a bad idea, but I went for the easy and simple solution.

So I will have to have another rev of the board.  The goal is still to have this system operational before summer sets in.