I'm trying to output RS232 commands to a device with a parallel port. The only problem is that the device is in New York and I'm in California, so I'm trying to make this as fool proof as possible for the person I have to ship it to (to test it for me).
Are there any special considerations I need to take into account with writing serial data to a parallel port? What pins on the DB25 would I use?
Thanks!
You would have to know exactly what the device with the parallel port expects. It's not obvious how you would pull this off.
The parallel and serial ports are different both electrically and mechanically. The parallel port has 8 datalines used to send one byte as 8 parallel bits to a printer, and a handfull of control lines to send different status signals back and forth between the PC and the printer.
The serial line works in a compleatly different way, sending one long stream of bits with start and stop bits in between.
Are you going to use the Arduino board as an intermediary device between the parallel device and the serial device ?
Thanks for the reply. Here's what I'm dealing with - I've got a video router with a DB25 input. I've got antiquated windows software sending data to the device over the user's choice of COM1-4. If I remember correctly, I think the last time we had it hooked up, we used the serial port output of the PC. Which I guess makes sense in that there is no parallel port option on the software.
I believe we used a DB9 to DB15 adapter to hook it up, which leads me to believe that a regular null-modem type adapter, or even just a DB25 port wired into the Arduino, would be sufficient to send it commands. I dumped the raw serial data output of the router's windows program into a text file so that I could decipher the commands (it doesn't check that the device is present for most commands). I now have strings of hex number commands that I would like put into an arduino, so that the arduino will "look" like the windows program to the video router device.
Because the router device is (most likely, it would seem) expecting serial communication over its DB25 port, I'm hoping it's as simple as RX, TX and GND?
ah yes that makes sense to me now basically a 25 pin serial interface as in the good old days. For a while i really thought you wanted to send serial data to a parallel por 
you might be able to find what you need here : RS232 Tutorial on Data Interface and cables
Wow, thats intense. I'll have to play around with it, I guess. Thanks!