[Oberon] HDMI question

[Skulski, Wojciech]

Magnus:

another hardware question. Is it safe to connect the Spartan-6 pins directly to the HDMI connector? There is some +5V lurking around the HDMI interface. The TMDS should be safe because it is terminated to 3.3V at the monitor side, but how about the CEC and I2C? In the Pipistrello schematics I can see some mysterious unlabeled box to the left of the HDMI (above the audio connector). What is that box? A bus switch or some voltage limiter perhaps? 

I am tempted to use my favorite SN74CB3T3306DCU in between the FPGA and the SCL/SDA from the HDMI connector. The ultimate protection would be to use a TMDS141RHAR redriver which can drive up to 5 meters of the HDMI to the monitor. Is it needed, or can the FPGA pack enough ooomph into the cable? 

I do not have actual experience with video HDMI. We used the HDMI gear to pump raw data between the FPGAs, but without actually dealing with video. Your experience would help!

Thank you,
Wojtek