[GPIO Expander] - Route isoSPI to GPIO Exander

[dyldonahue]

Current Features

Old method was just reading ADC directly - we now utilize a GPIO expander

Desired Additional Features

We know need to read therms through a GPIO expander. We have a drievr to read and write to this device, but we still need to package the isoSPI interface into this driver. Essentially, we want the read and write function pointers to point to our exisiting LTC driver functions, which are shown in the current code in the select_therms section.

Screenshots (as needed)

Here is the current "select therm" function. Most likely, we want to package the LTCwrcom and LTC stcomm is the read and write function pointers to the gpio exapnder driver. But, this might require a wrapper function to make the paramters line up

[dyldonahue]

@ameall after further thinking we dont actaully do any reading (since we cant have the return message sent back to the microcontroller over isoSPI), So, u can just use NULL and not worry about the read pointer. We only need to write to the expander to select therms