I have built an OctoX with and cannot get the lower motors (7,8,9,10 on the Mega) to initialize after power-up.
I have programmed the ESC's per the MultiWii "connecting the elements" description. I have connected the ESC's to the prescribed I/O on the flight controllers. I checked each ESC with a servo programmer to test the operation of ESC to motor, and all ESC's and motors operate the full RPM range. I have tried different variations of "MAXTHROTTLE" (1850 to 2000), "MINCOMMAND" (900 to 1300), "MOTOR_STOP", and the ESC calibration routine.
ESC: Turnigy Plush 40A
Batt: 2x Turnigy 5000mAh 60-130C
FC: MicroWii (I also tried the Flyduino Mega)
Software: MultiWii 2.1
I have successfully flown 6 other multicopter configurations (quad X, quad +, SingleCopter, Y-6, Flying Wing, Tri) over the last 1.5 years using the MultiWii software with great success. Thank you to the team!