I am just about to start a project using a Giga R1 and I have some questions I hope you will be able to offer some advice....
I see there are two I2C busses, if I wish to use one for sensors, and one for displays, how do I determine which bus is for which purpose?
I have had some problems with the original project which ran on a Mega. For some reason I seemed to kill some of the input pins (this happened randomly). So, rather than directly wiring sensors and switches to the input pins, I am going to use PC817C optocouplers.
Can I use the optocouplers for analogue as well as digital inputs?
Thank you for reading this, and I look forward to your replies.
Regarding I2C: Although both I2C buses might be available on pins, it's not said that the core supports both or only one. I suggest that you read up more on the Giga or ask the specific question how to use the second I2C bus in the dedicated Giga section: GIGA R1 - Arduino Forum
With regards to optocouplers; they will not work with analogue signals.
Note (you did not ask for this):
If libraries that you intend to use don't make use of the hardware abstraction layer, there is a good chance that they don't work with the Giga. You can test this before buying the Giga; you only need the core, the libraries of interest and the IDE.