Desperately needing help for time-crunched project with Simulink / Arduino

I am using an Arduino Mega R3 board to control 3 Hitec digital servos (HS-5645MG) using an analog input. The program is in Mathwork's Simulink (2012b). -Arduino powered through USB -Motors powered with 5V external power ~800 mA and common ground with Arduino -Input analog pin 4 using 'Arduino Analog Input' block. -Simulink blocks used to process input signal and determine motor angle based on thresholds. -Output digital pin 10 using 'Arduino Standard Servo Write' block.

The above setup is working great using some old analog servos that I had laying around, but when I try to do the exact same thing with the digital motors - NOTHING happens at all.

-If I use Simulink's Arduino Servo Sweep example model, the digital motors will sweep back and forth 180 degrees, using same power supplies described above. I am truly baffled as to what the problem could be!

Any ideas out there?

Thanks!

[Rolfe Dlugy-Hegwer]

Were you able to resolve this problem?