RS485 PWM controller

[richcj10]

I am using a ATmega328P uC with a TLC5940 (Used in a PWM Mode w/ pullups).
I use a MAX485 chip to receive the serial commands.  It works well with most motor controllers and all servos.
The one motor controller it doesn't work is the Vector Motor Controllers. I can't figure out why they don't like the signal(They think that the signal isn't there).  Attached is the schematic of the system. Any suggestions would be great!

Thanks,

Rick

[Kremmen]

Be more specific, please. What serial commands? Which protocol? What vector controllers? What commands?

[richcj10]

The board receives speed commands via a serial stream over RS485. The board sends out commands to the motor controllers via PWM.
This device (ATmega328P) handles logarithmic ramping / updating / and safety shutoff.
The motor controllers in question are the IFI VEX Pro Victor 88x.  I like these because of there rigidity for there price points.
But the draw back is they are very sensitive to the signal coming into them. They like to go into a fault condition representing a bad or no signal.
I have gotten them to work with a output Compare peripheral on a AVR.   

[amyk]

How about some scope/LA screenshots? Have you tried inspecting the signals?