Why do you have "PID" and "PID_comp"?? is "a" a tuning factor (as my "K") ??
Yes, one motor responses quicker/more than the other. I know this is sad, I didn't know it accepts -255 to 255. I though it was only 0-255.
Also if your loop is fixed time, you can omit the dt factor
I am unsure how you can exclude dt, my dt is not constant. How do you make it constant?
How did you find your P, I and D values? Well, their gains, kp, ki, kd?
Please let me know which Acc and Gyro models are buit on your specific Sparkfun board
I am using the generic 5DOF sensor which has a ADXL335 and IDG500, I think.
Forgot to add, I uploaded my pictures in my topic, to avoid cluttering your topic with my ugly system