[Felipe Navarro] wanted to add a few serial ports to his computer, but couldn’t find an adapter that suited his needs. So, he built his own.
His Quad Serial device is a nicely designed converter that offers four serial ports, two of which are isolated to avoid blowing up too much stuff if things go wrong. The other two are TTL ports, but with an interesting twist: feed them any voltage between 1.8 V and 5 V, and they will happily work with it, which is a lot easier than messing about with TTL to RS-232 converters.
It’s all built around an FTDI FT4232H chip, which has drivers available for most OSes, so it should work with pretty much anything. And, as [Felipe] notes, this chip has not been cloned, so you won’t have to worry about the FTDI drivers disabling your device without warning. Well, not at the moment, anyway. We did cover a similar quad serial port adapter last year, but this one is a bit more developed, with both DE-9 and screw terminal connectors available.