PMOD TDNext on MicroZED Carrier Card: I2C link

Question

I'm fiddling with a PMOD TDNext board on a MicroZED carrier card. I've got pinouts figured out and I've brought the I2C controller pins for one of the PS I2C devices out to the card. I've got a simple test program working that generates an I2C read of the PCA9534 on the TDNext board. I see from the scope that I'm generating the correct address and read command, but I'm getting an I2C NAK back. I've probed around and see that the signals are getting to the chip proper, and I see from the scope trace that it looks OK. It's just not working. There has got to be some simple, stupid thing I'm doing. Thoughts? I've attached a scope trace, and a picture of my setup. 
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steveicarus · Answer

Replying to my own question, with the answer. I was getting the NAK because I was not writing a command to set the read address, so the read attempt failed. I've now got it working.