Monday, January 21, 2013

Hacking a Cheap HobbyKing 6 Channel Receiver - Summed Signals

RC Hobby Receivers

Any standard modern hobby RC receiver works the same way. The position of joysticks is converted to a digital value, which is then encoded, modulated, and broadcast on some radio frequency. On the other end, a receiver demodulates and decodes the values, converts them to PWM (Pulse Width Modulation), and outputs each of the PWM signals on a separate output pin. Typically, you would plug in a servo or motor controller to each output.

The signal on each output looks like the following picture

And now let us zoom in on one of those pulses

The value of the PWM is the width of the pulse. Standard hobby electronics have a pulse width between 1000us and 2000us, or between 1ms and 2ms. A pulse of 1000us is equivalent to 0% and a pulse of 2000us equals 100%. In the picture above, you can see that the pulse is about 1.46ms wide, which translates to just under 50%, or the joystick is centered. There is no official standard for the time between pulses, but typically a pulse occurs around every 20ms for use with average analog servos.

The Problem

Often in robotics or, for example, fancy multirotor aircraft, there may be addition smarts on the vehicle that needs to do additional computation on the inputs. RC radio transmitters are great. They usually have 2 nice joysticks, a miriad of switches, excellent range, and input trimming built right in. It would be expensive and time consuming to build a remote control for your vehicle that matches the capabilities (such as range and features) of a cheap hobby remote control.

Unfortunately, to communicate the PWM signals from the receiver to the autopilot or cpu of your robot, 6 channels would require 6 inputs on your processor in addition to numerous wires from your receiver to controller. Conveniently, a number of receivers can be hacked to output a sum, or the combined PWM signal of all the channels on a single output. None are as cheap and as easy to hack as the Hobby King 2.4Ghz Receiver 6Ch V2

6 Output Signals on a Single Output Pin

Guess what? Whoever designed the HobbyKing 6 Channel Receiver did something very nice. The 7th output pin block (marked in the picture as 'BAT') is usually reserved for the battery connector or for the binding cord. On the HK 6 channel receiver, the 'BAT' signal actually outputs the combined signal of all the other 6th outputs. Just to verify, I hooked up the receiver to an o-scope and checked the signal. Below is a screen capture.

Here you can see that there are 6 distinct pulses from 3.3V to 0V, separated by 400us periods where the signal is low (0V). You can see in the screenshot that the 3rd channel or pulse, which on a typical airplane configuration is the throttle, is shorter than the others. Normally the throttle stays in the 'off' position or 0%, which is represented by a 1000us pulse, opposed to the other 5 signals that by default are at 50% or around a 1500us pulse. I can't wait to actually utilize this in my autopilot.

Compatible Transmitters

If you want a cheap control system for your robot/uav/fancy experimental aircraft, you can pick up one of these receivers and any of the following compatible transmitters from anywhere between $25-$60. Lowest cost for the features.


  1. The online shopping platform for remote controlled toys. Choose from a collection of a wide range of RC planes, RC helicopters and Bikes.Shop online.
    affordable remote control cars

    1. Hello It’s really a nice and helpful piece of info. I am happy that you shared this helpful info with us. Please stay us informed like this. Thank you for sharing. bye
      Tangki Panel
      Tangki Fiberglass
      Jual Septic Tank

  2. Very intelligent approach. I want to try this for my rc receiver!
    rc boats

  3. Well has any tried cPPM om the "BAT Port" to prove that it does work all 6 channels from one port?

  4. I someone has setup cPPMon this Rx then tell me how and what do you need to set it up?

  5. Looking for the top quality RC boats? Buy Rc Boats at VolgoPoint with free shipping all over the world.

  6. I read this article. I think You put a lot of effort to create this article. I appreciate your work. MINI EXTREME

  7. Psychics are asked a lot of unusual questions. One of the most far out psychic questions is as follows: Is my mobile phone being hacked? here

  8. I recently found many useful information in your website especially this blog page. Among the lots of comments on your articles. Thanks for sharing. brianclub dumps

  9. Keen online FPS Shooter fans will notice that this online multiplayer game is quite different to many other games considered to be in the same category FPS. the sims mobile hack android

  10. I've limited myself to live-action films even though some of the animated stuff is really cool.

  11. It's like writing a screenplay on spec, but you're dealing with a movie. Promoting and marketing a movie through social media is an absolute must.123 movie

  12. If you watch a movie more than once or twice then it is probably more beneficial for you to make that purchase, and stop wasting money on renting a movie over and over.


  13. For me the differences between those who call themselves a film critic and film reviewer are easy to see and I am sure there are many more differences which can be picked up on.0123movie

  14. That means in another 20 - 30 years time, those who have grown up on this swash of Super Hero movies will be the ones in charge making movies and you can bet there will be another resurgence in these movies.


  15. If you are looking for more information about flat rate locksmith Las Vegas check that right away. Carding Forum

  16. Yes, I am entirely agreed with this article, and I just want say that this article is very helpful and enlightening. I also have some precious piece of concerned info !!!!!!Thanks. justcbd discount

  17. Detective and hacking services. We offer our services in solving complex issues.

    Check treason.
    Help in business.
    Collection of information.
    Hacker services
    Hacking social networks
    Opening Crimes.
    The search for hiding.
    Search for the missing.
    Information that interests you.
    Help in resolving conflicts.
    Collection of compromising information, detailed information.
    Performance of work according to the plan of the customer.
    Any tasks are discussed.
    Prices for services are minimal.
    We work for the result.

    We carry out all types of detective services, we do it efficiently. Consultations are free.
    We select an individual type of assistance and make discounts for regular customers.
    We work around the clock.

    Hacking service: Hacking WhatsApp, Hacking Facebook, Hacking Snapchat, Hacking Instagram, Hack E-mail ang others

    WhatsApp:+1 581-703-2052

    The Best!

  18. You made such an interesting piece to read, giving every subject enlightenment for us to gain knowledge. Thanks for sharing the such information with us to read this... full spectrum cbd oil

  19. business logos A logo is a company's face. Apart from being its recognition, it reflects the personality and the unique identity of a company. Logos advertise a company's brand, principles, values and even more important,

  20. Positive site, where did u come up with the information on this posting? I'm pleased I discovered it though, ill be checking back soon to find out what additional posts you include. Best Darkweb Carding Forum

  21. You have performed a great job on this article. It’s very precise and highly qualitative. You have even managed to make it readable and easy to read. You have some real writing talent. Thank you so much. taxi tarieven amsterdam

  22. There are three android mobile phone apps that keep your phone safe. By safety, we are referring to the valuable data stored in your phone. gram scales

  23. Superbly written article, if only all bloggers offered the same content as you, the internet would be a far better place.. Hire a verified hacker

  24. Your article has piqued a lot of positive interest. I can see why since you have done such a good job of making it interesting. สล็อตโจ๊กเกอร์

  25. The only place you haven't hit me yet is on the bottom of my feet." I've been that losing cowboy on more than a few posts and reviews. Forums can be like a rowdy old west saloon. That's what makes them fun. Watch Movies Online Full HD

  26. Thank you a bunch for sharing this with all of us you actually realize what you are talking about! Bookmarked. Please also seek advice from my site =). We could have a hyperlink change contract between us! superslot

  27. I found that site very usefull and this survey is very cirious, I ' ve never seen a blog that demand a survey for this actions, very curious... live22

  28. Find out where and why things go wrong, and with their help get back on track? gogoanime - watch anime online

  29. Can I simply say that of a relief to seek out a person that in fact knows what theyre talking about on the web. You actually know how to bring an issue to light to make it important. Lots more people must check out this and see why side of the story. I cant think youre less popular simply because you certainly develop the gift. dark web sites

  30. Thank you for sharing excellent informations. Your site is very cool. I am impressed by the details that you’ve on this blog. It reveals how nicely you understand this subject. Bookmarked this website page, will come back for extra articles. You, my pal, ROCK! I found just the info I already searched all over the place and simply couldn’t come across. What a great web-site. White House Market Link

  31. Your website will be found in search engines as its coding will be in accordance with the latest web standards. Cheap web design

  32. Mobile apps are sure to remind you of their user-friendly and memory-efficient features. Instant apps are native apps that are more user-friendly, smaller and easier to use than traditional web apps. singapore mobile application developer

  33. Live Casino in San Diego – 2021 Review | CasinoNansGambling
    You can also choose to enjoy games from the Live Casino site. 승인 전화 없는 토토 사이트 The Live Casino site offers a variety of 영앤 리치 먹튀 games 승인전화없는 토토 꽁머니 and options. If you are a 12bet fan 포커 테이블 of online slots,

  34. Excellent blog! I found it while surfing around on Google. Content of this page is unique as well as well researched. Appreciate it. SMM