just use a DPDT switch
 Choosing the right kind of switch is important.
As the signal is a low voltage and low current you want a type of switch
where the contacts are self cleaning, like a rotary or slide switch.
but I'm wondering whether, for example, I can transmit both I2C data and the primary content data from a video IC
Yes and no.
Yes, in theory, you can -- but you have to translate it onto Ethernet, and then get it off. There's not an I2C pin on an Ethernet phy, nor is there an HDMI pin.
To get either of these working you'd have to get it into a processor, ...
I'm having a little trouble following what happened before you added the GPIO interrupt, and after. If I understand correctly, what was happening before you added it was:
After the first (correct) sequence, you come out of the ISR with xFlag_42 set, and so eventually you end up in __AppliSendBuff(&command42).
Midway through the __AppliSendBuff, the ...
The IC in itself should be fine. I didn't see anything in the datasheet which would indicate that it wouldn't work with the voltages or speeds you have in mind.
What I checked were the supply voltage characteristics and general voltage limitations on the pins.
I also checked that there is no indication of some DC blocking or differential signaling is going ...
For many years already, virtually all USB devices have implemented at least USB 2.0 protocol. This does not imply that they implement USB High Speed as it is optional in the USB 2.0 standard. They still profit from other USB 2.0 advances.
Implementing USB High Speed can be quite an effort for simple, inexpensive devices. The data speed cannot be handled by ...