Friday, I have to go take another look at our Church's theatrical lighting controller, which died yesterday in an electrical storm. The dimmer packs and computer all seem to work, but the communiction between them is suspect. (No remote control of lights/dimmers)
It uses a 3-wire RS-485 link (A-B and Ground?).
Friday, I want to put a scope on the computer end and just see if it's transmitting anything. Been a long time since I worked on RS-485.
Can I just scope the A or B lead to frame ground, or should I put a load from A or B to the Ground (3rd wire), or some other reference and measure that?
In short, what is the easiest way to scope an unknown RS-485 link, just to see if there's data being exchanged? I don't reall care what the data is: I am going to assume it's correct.
Oh, I should mention I'm also planning to swap out the LTC485 chips. The top was blown off one of them, which put a damper on further testing at that time.
Thanks!!