I dug through the chips in my office, and I didn’t see one of those in my drawers. I have an off-brand level-shifter, and I don’t want to lead you any further down the road of apples and oranges.
Again, you can run SleepySensor as an easy test. The sketch will put the MCU to sleep for 3 minutes. During this time, you can simply pull the I2C lines and confirm the current draw drops as expected. That should help you identify a target value, then you can see how the isolator you have compares to the target.
So I can confirm that using my code, the AL Notecarrier and a Swan if I pull the I2C lines after powering down the host I am seeing 12uA idle current which is awesome.
If re-read the discussion about isolating the I2C lines with the level shifter I need a way to access the hosts (Swan’s) MCU 3V3 supply so that I can power down the level shifter at the same time as the MCU. It seems that the only 3V3 output easily accessible from a header pin is from the Output Supply which is not the same as the MCU aka Main Supply, is powered directly from VMAIN, and has its own EN wired directly to MCU pin PE4 which is not exposed via a header pin.
If I were to use the Output Supply and pull the EN pin low via PE4 just before sleep I would no longer be able to communicate with the notecard in order to send the attn command
My plan was to use the Output Supply in order to power up and down my sensor.
Maybe I am missing something obvious ? Could I use the EN pin host side to provide power to the level shifter (I am assuming the current is signal level) and when its pulled low it would isolate the I2C lines ?
If I were to use the Output Supply and pull the EN pin low via PE4 just before sleep I would no longer be able to communicate with the notecard in order to send the attn command
What if you drove both the level-shifter EN and the Swan EN from the Notecard ATTN pin? Wouldn’t that give you the behavior you need?
So here we go, sleeping at ~10uA using a level shifter on the I2C lines Super happy about that!! Now I just need to figure out how to package all this up nicely. Thanks for your help @zfields and @bsatrom
I’m glad to see you were able to get this worked out. I think this progression will serve not only as a great reference for us, but for many customers to come.
Super happy about that!! Now I just need to figure out how to package all this up nicely. Thanks for your help 
