In this article we will discuss some of the latest ESC development and hot topics: BLHeli_S firmware, hardware PWM and 32 bit MCU. This article is created by Adriel Perkins.
BLHeli_S – New Firmware
BLHeli has released a 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. It’s specifically designed for new ESC’s such as the Aikon SEFM 30A ESC. Here’s what BlHeli_S is said to have improved as stated by SSKaug in the RC Groups thread listed here.
- BLHeli_S delivers a throttle response that is smoother than previous BLHeli, thanks to the hardware PWM. Two MCU’s support this for BLHeli_S, namely the BusyBee1 at 24MHz and the BusyBee2 at 48MHz.
- It will have the same good sync holding properties as base BLHeli.
- BLHeli_S does damped light only.
- It has motor PWM that is Synchronous to the MCU master clock, as it is generated by hardware. This makes the motor run more silently.
- It 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.
- Supports very high motor Speed: BB1 MCU can support up to 350k eRPM, and currently the BB2 is set to 500k eRPM.
- Supports regular 1-2ms input signal, as well as Oneshot125, Oneshot42 and Multishot. Auto-detected when the ESC sees an input signal.
All these improvements look promising and when reached, definitely will change the way our multirotors fly!
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.
Is 32 bit ESC better than 8 bit?
Currently the Aikon SEFM 30A ESC is the only ESC being tested with BlHeli_S on it. Of course, there will be many more ESCs to make the switch to BlHeli_S in the future. At the moment there are a few different options. Some of the best and most popular ESCs that will be competing with the Aikon ESC during its release are:
- KISS 24A RE ESCs
- DYS XM20A and 30A ESCs
- XRotor 30A and 40A (40A may also be BlHeli_S capable, unconfirmed)
- SEPM32 ESC
- VGood Firefly ESC
Three of these ESCs are actually using 32 bit processors on them. Being that they are 32 bit ESCs, they’re capable of much more processing and storage. These ESCs are the KISS24A RE ESCs, the SEPM32 ESCs, and the VGood Firefly ESCs. The other ESCs (pretty much all OTHER ESCs) use an 8 bit processor.
More processing power is generally better with every bit of technology. However, in this case there really isn’t a difference in actual performance. ESC’s are not even close to the 8 bit processing capacity at the moment. In the future 32 bits may become a requirement as coding gets more complex. Right now the only difference between the two is from a coding perspective. The 32 bit ESCs can be programmed in C++ because of the added bytes, but the 8 bit ESCs have to be programmed in assembly. Does it make a difference in practice? Only if you’re a programmer and only know C++ not assembly and cannot take the time to learn the syntax.
Personally, I’m very excited about the improvements BlHeli is going through. I’ve been flying BlHeli for a long time and even tried SimonK and others back in the day. It’s amazing how far ESCs have come and how much an improvement they have made to flight characteristics of multirotors. I look forward to testing these ESCs in the future and comparing them in real life situations to other ESCs. Keep your eyes out for them!
DATA FROM OSCAR LIANG'S BLOG.