@brother, for the headers, if not used as GPIO, I don’t think it needs to be labelled. But if you need, I need to ask the hardware engineer to give me one.

Do you mean the pin next to UART? it is 3.3V.

All the drivers for the card reader is in the firmware. If you insert MicroSD, it will be mounted automatically. One thing, when mounted, we use sync in the parameter. If you want faster speed, pls change to async.