First, I was the one who borked the azteeg, although it wasn’t my level shifter that did it.
I didn’t use the one on the wiki (after I discovered that I had followed a schematic that was just plain wrong – different azteeg revision that had an old school TTL high). It was just an NPN switch biased with a 10K resistor and a diode to protect from saturation. Simple switch to pull it down. The uC had a weak pull up enabled, so pull down was not necessary since current was limited to the sensor by a series resistor.
Yes, looking at Z sensors we should have just gotten the NPN sensor, not PNP. That would work. The PNP switch pulls up to high, whereas the NPN will simply close and pull down.
I did notice some anomalies in our azteeg the way it interacted with RE3D power supply.
1 - It was floating. This is often shitty for FET (see art of electronics). Some points were +14V relative to power supply ground.
2 - From uC ground off the regulator, my NIST cal. meter was measuring +6-+8V where we should have seen +5. I don’t have time to figure out if I was measuring from a floating ground or diode bias, or whatever, but that’s magic blue smoke material waiting to happen.
- I think that the azteeg was a poor match for this machine and not really well thought out by Re3D or azteeg V3 perhaps… Dunno.
So I would endorse any proposal for another controller, but we need to make sure we have a good star ground, and that chassis ground is corrrect. We were getting chassis ground in areas of the PCB where is was mounted to metal screws, and these may have been 10-14V away from +5 rails. It all seems kinda suspect to me, and others may be able to explain this better.
I did probably screw up a bit and tap my screwdriver somewhere wrong, but if GND was floating so high (and wasn’t supposed to be), even touching the damn thing could have blown it…
However, I want my magic blue smoke award, and deserve a place on the wall of fail now. I will gladly chip in for a new controller.