Some if the most obvious differences that I can see are as follows:
The 302E board does not have the LEDs “CVM POWERED” or “ALERT! PCIE/SATA POWERED UP”
The 500C board has some additional compoents which I’m not sure their purpose or the reasons for them. (Q34, Q35, D18)
I have no clue what other differences there are… or even if I’m chasing my own tail. I’m either running into some sort of difference of the i2c bus in the CSI interfaces (i2c conflicts?) or something similar.
I’m actually using the HDMI2CSI boards from Zhaw, and on the newer dev-kits we purchased, I’m seeing where the 2nd tc358840 fails to load the driver properly, complaining about an invalid chip ID. I’ve already switched out boards, and it made no difference. (I have quite a lot of these devkits and boards). If I put it on my older tx1 devkit (the 302E) I have no problems… and the chip ID is indeed correct.