rs485 pelco d

Speaker

I have ordered a chip to convert rs485 to an input suitable for the bs2.· I don't remember which one I ordered and that isn't the important part.· I am just trying to get a day or two ahead so I was just fiddling around.· On the scope the two inputs show a peak-to-peak a little over 10v.· I originally compared them to the voltage of the case of the dvr that is producing the signal.· To avoid using the case as a ground, I put several resistors in series between the two leads as a voltage divider.· I found a point that gave a slightly reduced peak.· I then used a zener diode to clip off most of the negative side and limit the positive side to something that wouldn't hurt an input.·· "Pelco-D cameras use No parity, 8 Data bits and 1 Stop bit, baud rate depends on your camera setting."· I used the preceding quote to determine the serin setting.· I got no result at all.· I tried looking for the input as hex, as ihex, and as string.· I got no results.· How can i tell if the stamp even sees my jury rigged input as a valid input?

Mike Green

If you want help, you have to provide and organize your information. I suggest a schematic drawing.

You need to look at your signal with an oscilloscope to make sure it's a logic level (+5V / 0V) signal and you should be able to see the data bits and make sure that they're roughly in the right format. I suspect that you're simply not providing the Stamp with anything meaningful. RS485 is a balanced signal as I recall and should be decoded that way. You could use an Op-Amp to provide a ground referenced signal that could be cleaned up and limited to logic levels.