***Question*** > *Problem in porting Rpi3B+ python GPIO PWM servo programs to Rpi4B* ***Answer*** > */ to continue, ...* ***References*** *[Rpi4B PCA9685 PWM Controller driving 4 TowerPro MG996R Servos - tlfong01][1]* *[PCAS9685 PWM Controller Installation Notes - tlfong01][2]* *[Rpi3B+ GPIO PWM Servo Testing Notes - tlfong01][3]* ***Appendices*** (1) Rpi4B PCA9685 and 4 TowerPro MG996Rs [![servo][4]][4] [1]: https://raspberrypi.stackexchange.com/questions/102115/slight-dip-on-the-gpio-5v-line-when-leds-are-on [2]: https://raspberrypi.stackexchange.com/questions/101095/rpi4b-raspbian-10-buster-circuit-python-blinka-installation-problem [3]: https://raspberrypi.stackexchange.com/questions/99408/pin-powered-pi-crashes-when-servos-move [4]: https://i.sstatic.net/06fVd.jpg