I was trying to implement an E-Ink solution using IMX7D. Unfortunately I only had a IMXEBOOKDC3 available, not the DC4 shown on the IMX7D E-Ink tutorials. After a couple of tries I found the right way of connecting the expansion board and the the definition of the arguments on U-boot to make the IMX7D and DC3 work together.
I logged these considerations on the blog post below:
http://bit.ly/IMX7D_IMXEBOOKDC3
Andres