Arduino -> Barco Projector


Arduino newbie here...but trying to get an Arduino to talk directly to a Barco projector via RS232. I've confirmed that I have my commands correct in comparing the commands that I send via my computer/hyperterminal and watching the rs232 output of the Arduino...the commands I send from the computer via RS232 to the projector work, but the exact same commands via Arduino do nothing. My hunch is that this is because the RS232 voltage levels coming out of the arduino are not to the +9v/-9v that the projector is looking for...

So, my question do I get the RS232 out of the Arduino up to the +9v/-9v RS232 spec??

Thanks so much!


MAX232 chip or one of its kin. Here’s one reference: There are also RS-232 shields, if you’d rather not bother, e.g.

Well, I have one of these (, but in comparing voltage out of my computer is around a constant -6v where out of the shifter is right about 0v...thoughts?

I should say that I am getting RS232 commands out of it if I connect straight up to my computer, can see commands coming from the Arduino through the shifter...but the projector is not happy with it...

Thanks for the quick reply tastewar!

The shifter board you have will be fine for communicating with modern computers, but if you’re talking to a device that expects true RS-232 (don’t know for certain if that is true of your device), you do need the MAX232 or equivalent, hassle though it may be.

Certainly appreciate your help here - so something like this?

Yes, that should do it. Don't forget to order the de-coupling caps at the same time!