I want to build a "hardcore" serial shield. Faster than the software implementation, with hardware handshake. I will try to work with the MAX3110E, communicating via SPI and probably use one DB9 socket on a protoshield.
It looks deceptively simple. Connect 5V, GND and pins 10-13 for SPI. Add a quartz, two small capacitors, a DB9 socket and you are done.
But if it is so simple, why hasn't it been done before? Or has it?