#garfield Logs

Jul 27 2025

12:50 PM aandrew: hm so I verified that I have the correct op-amp mounted (LMV321) and it isn't the "wrong" (alternate) pin ordering variant of the SOT23 by looking at the marking code and cross-referencing it
01:06 PM aandrew: in-circuit measuring of the resistors shows they are all 1k which is expected
01:06 PM aandrew: the voltage on the + input of the opamp is 0.4V, the output is at the positive rail though, and this is with the microcontroller out of circuit so it's not the micro doing something weird
01:06 PM aandrew: I might have to just leave it as is for now and not have pressure measurement
04:25 PM rue_mohr: erm, is it a rail-rail op-amp?
04:25 PM rue_mohr: hmm, rail-rail output...
04:26 PM rue_mohr: no, input is too
04:26 PM rue_mohr: huh
04:49 PM aandrew: yeah it's weird
04:55 PM rue_mohr: your sure the traces are right?
08:59 PM aandrew: I figured it out
08:59 PM aandrew: the opamp on the first analog input is kerfuckered
08:59 PM aandrew: output pin is only 5 ohms to +5V
09:00 PM aandrew: the opamp on the second AI is working as expected, so I just flipped over to that one
09:32 PM rue_mohr: ok