How do I let the tools know that my custom IP has buffers instantiated so that extra buffers are not added?
Edit the port definition of the relevant ports to add the following tags in the MPD file:
PORT LCD_IO = "", DIR = IO, VEC = [0:31], THREE_STATE=FALSE, IOB_STATE=BUF
In the example above, the port is called "my_io" and is a bidirectional port.
However the same rule applies to input or output ports as well, only the DIR attribute needs to be modified.