Remote speed control of nexus robot


I am trying to use a nexus robot 4WD Mecanum Wheel Mobile Arduino Robotics Car 10011 for remote speed control.Here is the link of robot.

Now we meet a problem about communication. We are trying to send speed command using ROS via serial port. When we test only communication between robot and PC port and it works. But when we are trying to send speed command to drive the wheels, it doesn't work when velocity command is above 200mm/s. So it means serial communication is OK, and the robot is OK too. We guess the problem is caused by interruption. Maybe the processor is not powerful enough. Could anyone provide a good solution for that? Could you provide some similar velocity control code if possible?


I would like to see your code.
Can you post it?