Serial Interface W/ Analogue/digital In/ouputs?

[lardman]

I'm after a general purpose digital/analogue input and output interface to connect up to a serial port, something like these:

http://www.velleman.be/ot/en/product/view/?id=351346
http://www.velleman.be/ot/en/product/view/?id=9383

just that I'd prefer it to use serial so that it's more compatible with the various PDAs I have lying about (Zaurus will do usb and serial, Psion will do Parallel and serial).

Thanks,


Si