Hello @Bipman
by default Port A is meant for I2C, but it can be used for I/O (Port B) or UART (Port C) as well.
Note: But please be aware, that it can be only one type of port at any given time. Also, since its default use is Port A (I2C) there are internal pull-up resistors (10 k) in place on both lines which might have a negative effect when used in a different mode.
If you need Port A and Port B at the same time there is the PbHUB unit which can be used to connect some of the Port B units.
If you need all three types of ports (A, B and C) together then I am afraid M5Cardputer is the wrong device to use as core. There are simply no more GPIOs available for a dedicated Port B and/or Port C. Please see schematic here.
Thanks
Felix