Tag Archives: blheli

HobbyWing XRotor 15A ESC with “OneShot” and Damped Light

Two weeks ago I posted an article about the XRotor 10A ESC, which I wanted to use for my next acro quadcopter. I wanted to download the English manual from the HobbyWing website and noticed these new XRotor 15A ESC. The XRotor 10A performs in my opinion great compared to the SimonK and BLHeli and HobbyWing claim these new XRotor 15A are even better than SimonK and BLHeli ESCs. I wanted to know what the difference is and asked the HobbyWing support team. This is the info that I got:

  • The new XRotor 15A does not support signals with refresh rate up to 621Hz like the 10A version.
  • The new XRotor 15A support “OneShot” and “DEO” (which is like “Damped light” on BLHeli or comp_pwm and motor_brake on SimonK). The old 10A ESC does not support these functions.

HobbyWing made some tests and claim that these new ESCs have better efficiency and lower temperature. So I decided to give these ESC a try and ordered 4pieces for the acro quad.

The ESCs came extreme quickly from Hong Kong to Germany, only 10 days. Before I mount them on the quadcopter I wanted to know what’s inside under the heat shrink, so opened one and made some photos.

The ESCs are a bit bigger and heavier than the XRotor 10A. Unlike them these have longer motor cables and some other type of gold connectors.


On the backside you can see the IRFH8318 MOSFETs. These are rated to 30V, so maybe flying on 4S could be possible. Here you can find the datasheet.


On the front side the XRotor 15A is completely different from the XRotor 10A. I will check and ask what the elements exactly are, as I cant find any information right now.


  • MPSF34 / MP6530 – Brushless DC Motor Pre-Driver by Monolithic Power Systems (Max 60V).
  • HW503 / 515AB – I can’t find any information about this chip. (Thanks to QuadMcFly from RCGroups, who corrected me, that it is not HH503).

I will update the article as soon as I mount these on my SG Acro v1.1 quadcopter with the T-Motor MN2206 and give them a try.

Update 30.09.2015: The ESCs are already mounted on my acro quadcopter and they perform very well. OneShot is activated and I have no sync issues with the T-Motor MN2206. Active breaking is about the same as on HK BlueSeries 12A with BLHeli, but in my opinion not so great as SimonK with comp_pwm and motor_brake enabled. The ESCs are rated for max 3S, but I have tested them successfully on 4S with no problems. They don’t get warm and I haven’t experienced sync issues. Here a picture of my SG Acro v1.1 with the ESCs heatshrinked directly on the arms. I can’t tell for sure if these ESCs have higher efficiency than BLHeli or SimonK ESCs, as this is hard to test without a power meter. If this helps you, I got about 14min mixed flight time (Quad weight is 270g without the 4S 1300mAh battery; props are 6” carbon).DSC_3436

SimonK vs. BLHeli firmware vs. T-Motor 10A Air ESC

Both SimonK and BLHeli firmwares are getting updates, new features and I was wondering which of these is better for my quadcopter. Since I started with the multirotors I was using the SimonK firmware and I am still happy with it. I also will test one T-Motor 10A Air ESC, which has its own firmware.

On four different ESCs I flashed the following versions and functions of the firmwares:

  • SimonK 2014-09-30
  • SimonK 2014-09-30 comp_pwm enabled (here is an article on how-to enabled it)
  • SimonK 2015-04-19 comp_pwm enabled (support “OneShot125”)
  • BLHeli 13.2 damped light enabled (support “OneShot125”)


comp_pwm disabled vs. comp_pwm enabled vs. damped light comparison:

There is a significant difference between the SimonK firmware with enabled and disabled comp_pwm feature. The motor on the ESC without the comp_pwm stops probably a second later. On the other side the ESC with the BLHeli 13.2 and damped light stops even faster than the one with SimonK and comp_pwm. So 1-0 for BLHeli over SimonK. I was corrected on the RCGroups forum, that I didn’t enable the “MOTOR_BRAKE” feature on SimonK, so the comparison is not exactly right. I will test that too and update this article.

Then I decided to compare the BLHeli 13.2 and the SimonK 2015-04-19, as both support the “OneShot125”. Well here I found the SimonK better and smoother than the BLHeli ESC. The motor on the SimonK ESC was much quieter. 1-1 SimonK vs. BLHeli. Note: I used the standard settings on BLHeli, so there could be an option to change, that will make it perform better.

The T-Motor 12A Air ESC with its stock firmware does not have a feature like comp_pwm and damped light, so it behaved like the normal SimonK firmware. The motor was very responsive and its sound was also very quite. It is a bit subjective, but I think it performs like the SimonK with the “OneShot125” or even better. It is also a bit lighter (7.3g) and smaller than the HK BlueSeries 12A ESC.


Please note that I only tested one type of ESC (HK BlueSeries 12A) and one type of motor (T-Motor MN2206 2000kv) on a 3S battery. The results can be different on other configurations.

Conclusion: The damped light on the BLHeli is a bit better (*to be updated) than the comp_pwm on SimonK, but the last one performs in my opinion much better in “OneShot125” mode.

How to flash SimonK and enable comp_pwm

Many of the ESCs on the market have their own firmware and are not optimized for using in multicopters. The solution to this problem is to flash a special firmware on these. Note: Not all of the ESCs can be flashed with these firmwares. Check this list to see which ESCs are supported.

Two of the most used firmwares are the SimonK and BLHeli. Which one is better is hardly to say, especially when using different type of motors. Here I will show you, how to flash the SimonK firmware on an HK BlueSeries 12a ESC and more importantly how to enable the comp_pwm function on it.

But what is comp_pwm? It is not exact the same thing as damped light on BLHeli, but it performs a bit like an ESC with damped light function enabled. On the KISS ESCs it is called active freewheeling. It switches the passive MOSFET on your ESC “ON” during the freewheeling phases and by this reducing the power loss. If you want to learn more about PWM and active freewheeling, watch this video here.

Back to damped light or regenerative braking: what does it do? When you reduce the throttle the motor does not stop immediately. When comp_pwm is enabled, it also helps the ESC to stop the motor faster. This allows faster response of your copter. This video shows it very clear. Note: I am not sure if the guy in the video has enabled the comp_pwm feature on the ESC with the SimonK 2014-09-30 firmware. On SimonK firmware the alternative of damped light is called “MOTOR_BRAKE” and can also be enabled.

You will need the following tools to flash the SimonK or BLHeli firmware on your ESC:

  • An ISP Programmer – USBasp AVR Programming Device for ATMEL; you can also use an Arduino as ISP device, but it is easier with the USBasp. If you still want to use the Arduino check how to do it on this page. You will need to install the drivers for it too.
  • Atmel Atmega Socket Firmware Flashing Tool. On some ESCs, that have pads on the PCB board you can even do it without this tool. I have done it once on my HK BlueSeries 30A, but it is much much easier with that tool. It is worth every penny and saved me so much time.

There are several software applications you use to flash the firmware. I have always used the KKmulticopter Flash Tool. If you want to enable the comp_pwm function you will need the latest version 0.80 beta 6.

I will show you how to do the flashing with the KKmulticopter Flash Tool. Plug the USBasp into your PCs USB-port. If you are using the Atmega Socket Firmware Flashing Tool connect it to the USBasp device.


If you have decided to do it without the tool, connect the pins of your USBasp device with cables to the pads of your ESC (you need to identify the MISO, MOSI, GND, VCC, SCK and RESET pads on your ESC).


Once everything is connected you need to supply power to the ESC. It is not recommended to use a LiPo battery as a external power supply, so do it on your own risk.

Start the KKmulticopter Flash Tool. Choose the USBasp as a programmer. Then choose your ESC type. As said I will be flashing my HK BlueSeries 12a, which has an atmega8 (note: most of the ESCs on the market has this one or a Silabs-chip). Be sure to choose the one “+ enable Bootloader”, so you can later flash new firmware easily trough the servo-cable of the ESC.

It is very important to flash the right firmware on the ESC or you can damage it. The list with the supported ESCs on top of this page tells you, which one is the right for you. Last but not least you can define the firmware version. The latest one SimonK from 2015-04-19 support another useful function called “OneShot125”. It is a modification on how the flight controller and the ESC communicate between each other. It should give us a more responsive system, but there could be issues with some ESCs and motors.


If you don’t want to enable comp_pwm, you need only to click on the green button and the firmware will be flashed to the ESC. You should get the “Flashing of firmware was successful” message.

If you want to get use of the feature click on the “SimonK Firmware Compiler”-Tab. Select the version, click Download on the right and choose again the right one for your ESC. Then on the tgy.asm-Tab scroll down to the line where COMP_PWM is defined. To use enable it replace the “0” with “1”, click “Save” and then “Compile”. The newly created file is ready to flash and you can click on the green button to flash it on the ESC. That’s it 🙂