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I got these to work, and I like them... 
I'm using obsolete Parallax (SX-28) microcontrollers (but I assume they're all about the same)...
--- these were tricky. I kept getting no response except for the reset. Finally I set up some LED's and just observed (sampled EVERY TWO micro-seconds) so that I could see the unit's responses --- it was faster than I had ever expected: my program had been too slow. I then programmed my "sampling" right into the middle of those observed responses - and the units work really well...
--- also, they usually take another reset for a another function to be performed...
--- I could query each unit's serial number, (and write it down) so I didn't have to bother with the CRC; instead, I just ignore (try, try, again) any response that is not approximately what I was expecting.
--- "everything" is inside the simple, 3-lead chip -- so I will use the cheaper single chip -- I do not know the benefits of the same chip mounted on a card for an extra $4.
New board 
The pinout has changed from GVD to GDV, now labeled, one larger mounting hole above header pins, unpopulated J2 has (4) through holes, J3 (2).
ALL ELECTRONICS REPLY: Thanks - we've updated the picture to the current version going out as of 2-22-18.
