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I have a PCB assembly where I built the circuit in the schematic below. I did not start programming yet.

enter image description here

I'm getting the weirdest problem. When I check the voltages in the SDA and SCL lines (which should be 5 V because of the pull-up resistors) I get values close to 0.7 V. I try de-soldering the isolator and check the voltages again, with only the INA219 circuit assembled and I got another weird result the SCL line has a value of 4.8 V and the SDA line gets a result close to 0.7 V.

Can anyone help me debug this circuit?

devnull
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André Oliveira
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  • No faults in the schematic, but check voltages on every pin and suspect wiring connection faults or IC damage – Tony Stewart EE75 May 10 '22 at 12:17
  • Is the MCU side pulled up with resistors? What value? To which voltage? Is it a 5V MCU? – Justme May 10 '22 at 12:21
  • @TonyStewartEE75 i doubt it will be a damaged IC i build the same circuit in another board and got the same results – André Oliveira May 10 '22 at 13:09
  • @Justme The MCU side is pulled up to 5 V with 4.7k resistors, and i m suplling the mcu (avr128da32 ) with 5 V – André Oliveira May 10 '22 at 13:14
  • Given the non-inverting simple transfer function, Test all voltages and impedances with a load. Then CM noise can be shunted with an RF cap. for testing purposes. I suspect that noise will be large between grounds – Tony Stewart EE75 May 10 '22 at 15:17

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