simple abstract communication question

Could I link Arduino to a DB9 port by connecting the Tx/Rx pins, RTS/CTS, and ground? Or is Computer Serial 12V instead of 5V?

PCs with real serial ports use 12V signals. They are not good for an Arduino. There are converter chips, MAX232, that drop the 12V to 5V and invert it (required).

Computers are ±12v, direct connection will blow your Arduino.

You can either use a MAX232/202 or similar chip or rig up a few components. There was a thread just the other day that had a transistor interface.


alright, thanks. Have an older 1997 laptop that originally had Win95 on it, I put 2000 on it on a spare 1GB HDD (kept the 95 for show and tell down the road) that doesnt have USB, thought I could make it kind of a scrollable display station for serial output from arduino with puTTY, that I wouldnt have to worry about having any value for theft. The PCMCIA slots are too slow for USB boards.