Thanks, I'll try this.

> As it came it was 0x27 Dec 39 but I had to double it for pbp to 0x4e dec 78.
$27 is the code not counting the R/W bit. Some people shift this one bit and add the R/W bit making $4E and $4F.
This is clear in the Ti or NXP expander datasheets.

There are pullups on my boards. The signals look clean.

My hardware looks more like this:

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