I'll be hacking a PWM servo to have positional feedback for ARC using an EZ-B v4. You can also perform the same functionality with an Arduino or IoTiny on EZ-Builder. I'm merely using a EZ-B v4 because I'd like to play with my EZ-Robot JD Humanoid during the hack as well :).
You can read the servo positions of a pwm servo using this hack. Adding an extra wire to the PWM servos by reading the potentiometer position allows you to know the position of the servo at all times by the ADC input of an EZB.
I will be using these two robot skills....
1) Reading positions with the 8 onboard EZ-Robot EZB v4 controller: https://synthiam.com/Support/Skills/Servo/PWM-Servo-Feedback-ADC?id=18047
2) Reading additional ADC positions from an arduino over I2C to the main controller: https://synthiam.com/Support/Skills/Servo/PWM-Servo-Feedback-i2c?id=18069