I'm not one much for understanding schematics, but I'm trying to figure out on the accessory connector you have an Ain2 and an Ain3. Are those auxiliary inputs, or analog inputs? I'm looking for an analog input so that I can monitor external battery voltage. And I'm not sure if the board has an ADC built into it or if I have to connect one externally.
Also I noticed on there that one of the pins is labeled rx and one is labeled tx. Do those forward through to the serial port on the raspberry pi, or are they for something else?