Signal between FC and ESCs


Hi, This is Haozheng and I’m really new into the Drone design and flight controller. I am doing a research project on applying alternative power supplies onto quadcopter. The question I got is that will the open source FC be able to provide me with the signal between FC and ESCs? The reason why I want to obtain this signal is that I need this command to be able to let our alternative power supply know how much power it needs to output to drive the propeller at right speed. If so, which FC would you recommend me to start learning with? Btw, our drone will be really heavy (~200 kg). But we got enough thrust from the propeller and power supply, just not sure if there is any FC can do the job to command such high thrust and weight. Thank you so much for your precious help and input!


A lot of Flight Controllers are open source firmware, but if you examine the pages and pages of parameters stored in one of these beasts, you might take fright at the thought of jumping into the code. Perhaps you are confident? But what would that gain you? A “signal between the FC and the ESCs” you say. To me that is the same as the standard motor output lines from the controller, going to the ESC’s, PWM signals. The ESC (motor driver device) just needs re-invented for your purposes, your “power supply”
Don’t think of messing with the complexities of individual motor control/harmonisation. Let the FC do its job. A recommendation for a FC? Everyone will have his own opinion. I like the PX4 variety, the pixracer being a small and very capable example.
You need PC software to talk to the FC. Mission Planner is a well established option. I have grown used to QGroundControl myself.


Hi KJBB, Thank you so much for the info and help~ Yeah, I do see the complexity in understanding the PWMs and would never want to try it :smile: I searched and found that there is a new method called “one shot” that will send signal directly from FC to the motor to commend its speed. I want to ask does PX4 has that capability?
For the software, would you recommend Mission Planner or QGroundControl? I saw many people use the second one, but I am not sure which one is more suitable for our project. Since we won’t use ESC to commend the motor as we plan to use alternative power supply for the propeller, which ground station software do you think would provide more flexibility on that?
Thank you a lot for the input!


One Shot is an alternative ESC (Electronic Speed Controller) it is faster basically. It sends “one shot” of the signal every flight controller loop, and it does this as soon as the Flight Controller has a new value for the ESC. (I am guessing maybe this why it’s called “oneshot” :slight_smile: ). It waits for a change before firing another “shot”

You still need some kind of ESC, even if it is a One Shot style. No way will the puny signals from the Flight Controller fire up a motor, and in any case the ESC must convert PWM signals to three wire motor drive (normally). ESCs assume an electric brushless motor. You can deliver a KW to a high power motor with a big enough ESC. You have said nothing about how you intend to drive your motors - what “alternative power supply” they use. If other than a brushless motor, you may need to invent your own Speed Controller, and examine the One-Shot or PWM ESCs to see how to convert.

I would go with QGroundControl, but I may be biased. Others would say Mission Planner. In truth either is flexible enough for your needs.


Hi KJBB, Thanks for the Reply. The power source is currently still confidential and we are in test phase. I will try to follow the beginner’s guide and get started~