How to add minimum 3 serial ports to a Raspberry Pi?

Question

How to add at minimum 3 serial ports to a Raspberry Pi?

I thought about:

1) On hardware

2) On USB

For the the second one i thought about some circuit that exposes 3 serial ports and has an USB port that connects to the Pi. I.e.

                 |===COM1
USB=======circuit|===COM2
                 |===COM3

@pjc50 but is there a chip that can do like a hub to do a micro HUB
Acutally I think this is the device you want: ftdichip.com/Products/ICs/FT4232H.htm
@pjc50 Yes it is! now i look for prototyping version THANKS +1
You see, this is exactly the reason I sneer at the Open Hardware community's efforts with Raspberry Pi. I think that the Arduino itself is an overkill for most projects, as far as computational power goes (how much MIPS do you need to light an LED?). And here is a prime example. The Raspberry Pi is packed with tons of stuff most people won't be able to use, and you still want to complement its functionality with external circuitry. You paid plenty for the Pi, I'm sure what you want to accomplish can be done by software alone. If you're unable to write that code, downgrade to cheaper kits.

pjc50 · Accepted Answer · 2012-12-05 15:06:14Z

If you want a ready built module from FTDI:

Otherwise build around the FT4232H. (Moved this to an answer so you can mark it accepted)

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