RS-232 on BeagleBone

Hi,
I'm hoping to use the Beaglebone as an embedded controller for a
instrument (scientific, not musical).
My plan was to save the trouble of building a custom board initially
and focus on the software and getting a prototype working. The board
will arrive in a few days....

It will need to control an external comercial power supply serially
via RS-232 or RS-485.

The question is:

Can I do this with the beaglebone pinout directly (ie connect pins
from the expansion headers to the -232/485 directly), or do I need to
add a driver chip on a cape?

Thanks

You will need to add a driver chip on a Cape.

Gerald

Hi Adam,
The serial interface is 3.3v so yes you will need some sort of level translation. In a pinch you might checkout the offering from Sparkfun.

http://www.sparkfun.com/products/133
http://www.sparkfun.com/products/449

I haven't used one of these so I can't vouch for how well they work, but they look simple enough and should work with 3.3v.

Mark

Another option might be getting a USB<>485/232 tail if you are against wiring up a level translator.

A USB to serial cable would certainly be the easiest, least elegant way to do it.

You definitely need a level shifter to go from board to rs232 voltage levels. Sparkfun and Pololu both sell them for > $15. Then, you would need to go in and deal with the pin mux and setting up the device. If you are a kernel hacker type, it should be straight forward enough. That's for 232; 485 is a different matter and I think you'd have to go from parts to build that.

As I started with, if all you want is for it to work, get a USB to serial cable. I have ones from parallax and ones from staples. Most of them don't even need drivers installed, they just work out of the box.

wjr