Posted by Mark Spencer 6 years, 1 month ago
Multi-rotors scene witnessed boom in popularity in last several years welcoming seasoned RC enthusiasts as well as professionals seeking for steady filming platforms. RC industry is lazy in response to the market demands and in the first years we've witnessed bunch of pioneering work in the field. Usually electronics used were not actually designed for the purpose of multi-copter flight and some of the interesting modifications were made, such as the work on Open Source Firmware of ATmega-based brushless ESCs by Simon Kirby, or widely known as SimonK firmware for multi-copter ESCs. So what are SimonK firmware advantages?
Brushless ESC's used for fixed wing aircrafts and helicopters have certain properties that are not very welcomed with multi-copters.
One of the main disadvantages of cheap ATmega based brushless ESC's is refresh rate of 8hz which is well suited for the fixed wing aircrafts but not for the multi-rotors. Now why is that?
In real-life terms refresh rate is directly affecting response time of the motor to the given command. Usually this command to change the speed of the motor is issued by man, relayed trough the radio link to the aircraft and feedback perceived by the human eye, with each of the hops adding in a bit of latency making the refresh rate of 8 per second (Hz) more than enough to do the job.
With multi-copters most of the stability and control is achieved with the control board which is issuing subtle commands to each of the motors to keep the aircraft in e.g. steady hovering with headwind and difference between 8Hz and 400Hz makes the difference between the stable and unsettled flight.
Main SimonK firmware advantage is resolution of this issue changing 8Hz response time to 400-490Hz depending on the hardware's capabilities. Maximum theoretical limit of the refresh rate is 500Hz because of the maximum pulse width of the PWM signal which is 2 milliseconds.
Firmware is also stripped of some other unwanted functionalities such as the LVC (low voltage cutoff) or start-up delay making it even faster.
You don't want power to the motors suddenly cutting off, 100 meters altitude even if the batteries are running low.
One thing to have in mind is that ESC's flashed with SimonK firmware usually can't be flashed back (because there is usually no original firmware available) and might not be suitable for other usage.
For example instantaneous throttle response might strip the gears on a CP helicopter or overload folding spinner on a glider.
To put it in layman's terms your multi-copter will be quieter, more locked in feel once tuned, with descending much smoother with less wobble and better wind handling.
SimonK Open Source Firmware for ATmega-based Brushless ESCs can be found on this link.