I2C - PCA9555 and PCA9554

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by Dave on Tue Aug 21 10:20:07 MST 2012
I'm interfacing the PCA9555 and PCA9554 to my LPC1788 using the P82B96 drivers, and came across an interesting situation.  Perhaps there are others out there doing the same thing?

The interface looks like this (that's an RJ45 Ethernet connector on the right)

So, for diagnostic purposes, I connected all 8 pins on the PCA9554 to the lower 8 bits of the PCA9555, and wrote a test loop that sends test bytes out to the PCA9554, then reads them back from the PCA9555 (ignoring the upper 8 bits).