Features:

BLHeli_S is an improved version of the base BLHeli code. It comes with new code geared for new hardware in ESC’s (electronic speed controllers). It uses the BLHeli 14.5 base firmware revision and improves upon it.  

In terms of firmware, compared to the the previous version of BLHeli:

1. BLHeli_S delivers a throttle response that is Smooth as Silk, and the main factor contributing to this, is that it uses hardware to generate motor PWM. Two MCUs support this for BLHeli_S, namely the BusyBee1 at 24MHz (EFM8BB10F8) and the BusyBee2 at 48MHz (EFM8BB21F16).

2. BLHeli_S has good Sync holding properties even not better.

3. You cannot switched off damped light.

4. BLHeli_S has motor PWM that is Synchronous to the MCU master clock, as it is generated by hardware. This makes the motor Silent.

5. BLHeli_S has very Small throttle Steps. The resolution varies between hardware configurations (MCU clock speed and driver type), and is between a nominal 512 steps and 2048 steps.

6. BLHeli_S supports very high motor Speeds. A BB1 MCU will support 350k erpm, and the limit of the BB2 is not yet known, so the code is set to limit at 500k erpm.

7. BLHeli_S supports regular 1-2ms input signal, as well as Oneshot125, Oneshot42 and Multishot. Autodetected when the ESC sees an input signal.

8. Configuration and setting up is the same as regular BLHeli ESC, you can program the ESC through FC.

If you have a regular setup, just install and go fly (calibrate if your throttle range does not match BLHeli_S default). Or if you need to configure or update, just do so with the Simplicity offered by connecting to your ESCs through the FlightController, using BLHeliSuite and a USB cable.

Hardware Changes:

The changes in programming are directly related to the ability of improved hardware that is being implemented. As SSKaug mentioned, this new line of ESCs are running the BusyBee1 (EFM8BB10F8) and the BusyBee2 (EFM8BB21F16) MCU’s (Microcontroller Units). These two MCU’s are different than the previous Silabs chips that many ESC’s have been using. The reason these MCUs are going to be better is because instead of using software PWM they will be using hardware PWM that is synced to duty cycle.

The great thing about using dedicated hardware to generate the PWM is that the speed at which the ESC writes the values to the motors is doubled! With old Blheli ESCs and software generated PWM signals, the ESCs write to the motors at a 16khz rate. With hardware generated PWM it’s bumped up to 36khz. These means that your motors are getting input even faster which allows for better response. KISS ESC’s are an example of this. They have hardware generated PWM and the smoothness and response you get with those is hard to beat.

All these improvements look promising and when reached, definitely will change the way our multirotors fly!