Hi hellolv,
Could you tell me more about your setup? Are you using an NI RS-485 interface to communicate with your device? Also what program are you using to communicate with your device?
If you are using LabVIEW with an NI RS-485 interface, you could try running one of the LabVIEW examples. To get there, go to Help > Find Examples > Browse by task > Hardware Input and Output > Serial > NI RS-485 Transceiver Control.vi. If you see no problems there, there might be an issue with the program that you are using to communicate with the device.
You might want to doublecheck your baud and parity settings and make sure this is correct. There is a lengthy discussion on the same behavior you are experiencing
here.Hope that helps!
Rasheel