Phottix Odin Canon 6D/430exII setup for Noob

I'm wondering how to get the TTL function to work with my Canon 6D and 438EXII using the Phottix Odin. If I put the flash in TTL, I can control it in 'M' mode on the control unit, but when I put the control unit in 'TTL' mode, it just fires full blast and over exposes everything. Is there a setting in the camera flash menu I need to select? I made sure that both the transmitter and receiver are firmware 1.24. Apart from TTL, it functions perfectly.

I guess this will help me develop manual flash skills.