RS485 communication Noise

1. Try to reduce connection speed. For instance if you have 57600 change it to 19200 or even 9600.

2. Make measurment of RS485 with scope for applying terminating resistors.

3. Employ RS485 repeater with optic isolation.

4. Use check sum data transmitting technique.

5. Use majoritary data sending technique.

6. Use twisted pair wire.

There are common recommendations for power supply filtering, shielding and etc. which you can google independently.

Good luck.

power filtering = www.furman.com , www.apc.com , www.monstercable.com

First define noise, what type do you mean? Corrupted electrical? Audio?

Ground wire- you can sometimes eliminate some noise by adding a separate wire wound around the other not in the usual twisted pair sort but looped, if a 1' ground then wind every 2" and connect to ground lug at each end.

Make sure that the drive and the motors are grounded properly. Do not ground the shield of the communication cable at both ends, it would allow noise to flow through it. The drive control and the receivers must be at similar ground levels if a communication link isolator is not used.

Try googling "RS485 cheat sheet" for answers

Noise in 485 comms. is invariably during the tri-state period not the active period. Try biasing the termination.