The brushless motor controller is a Mi-3A brushless ESC. It is designed for 1S lipo battery usage, putting the voltage in the range of 3.7-4.3v. Some websites may indicate 5v, but our experience says running this ESC at 5v is a bad idea, despite what the spec sheets might say. Our solution to this was to develop a super capacitor board that separates the 5v rail from the ESC, while delivering a Super-Capacitor supported 4.3v to the ESC.
This ESC is PWM controlled and serves our purpose quite well. I2C would be better, and given that the heart of this ESC is an Silicon Labs F330 microcontroller, we are considering a future enhancement of I2C to the firmware.
The firmware is the open source BL Heli ESC firmware. For our purposes, Aero-based ESC firmware is overkill. The startup procedures for the ESC are problematic when the incoming power is unable to sustain the droop caused when the motor is started up.
I2C would be a great benefit, since the main CPU would be able to inquire the ESC of it's status, as well as motor RPM. For more precision attitude control, motor RPM will be essential.
Until we develop our own ESC boards based on this design, you can find out more here:https://hobbyking.com/en_us/supermicro-systems-brushless-esc-3a-mi-3a.html