I am working on my BS in EE. I am building a drone for some handicap member of my community. I am currently using a PDB-XT60 and HAKRC F405. I was driving my brushless stepper motor with a raspberry pi using a PWM. However I was informed that I would need to use the HAKRC F405 to control the drone because it has a built in gyro. I was able to vary the motor from 1100-1500 on the pi. I am currently in beta flight and the motor only spins at 1910 exactly. Does anyone know the cause of something like this?