A Quick Look @ ESC Communication Protocols
With all the different names flying around, PWN, Oneshot, Multishot, and Dshot. How do you know what to look for? Well, some of that is pretty technical, but this is a quick look at all of the current ESC Communication Protocols found on today’s quadcopters.
ESC Communcation Protocols – What does it all mean?
When it comes to ESCs, you normally hear of two terms, how many amps they can handle, and what kind of communication protocol they are capable of. Oneshot, Multishot, Dshot ect. But what does that mean, and why do all these names have shot in them? Well, I don’t really understand the whole shot thing. but I can tell you some of the differences between all of these protocols, so grab a drink and lets get started.
What the communication protocol is and does
To start, we should explain what a communication protocol is, and much of it is in the name, the communication protocol is the way that the ESC’s and the flight controller speak to each other. Think of it as a married couple having a conversation, clear, direct, uninterrupted communication will probably get things done quicker than unclear, arguing where they constantly interrupt each other.
So lets start with the basic, PWM, or pulse width modulation has been the defacto standard in ESC communication until this last year. And although the oldest and slowest, is still generally supported by most new hardware as well. Basically, the wider the pulses, the more throttle. However, this is form of communication is the slowest and has the most latency, and is often subject to de-synced signals known as jitter.
Oneshot aimed to fix this, and was the first of our modern protocols to arrive to the scene. The firmware developers decided sync the ESC signal to the PID loop of the flight controller, removing the jitter of PWM, they also used a shorter signal width, making communication between the flight controller and the esc much quicker, improving response. In short, Oneshot 125 is 8x faster than the original PWM protocol.
Oneshot 125 was only introduced in 2015, but we still have a long way to go in this list thanks to the boom of acrobatic quadcopters and quad racing.
The next new kid to the scene was an advancement to the Oneshot protocol called Oneshot 42. The fact that 42 sounds less than 125 led to much confusion, but the 42 is indeed faster than the 125 version. Being 3x faster than Oneshot 125, and 24x faster than PWM.
While the world was being excited about the advancement of Oneshot over PWM the developers over at RS2K were working on two major projects. One of these was Raceflight that we are not going to cover here but the other was Multishot.
Multishot was a protocol completely different from Oneshot, considerably faster, and had some pretty high hardware requirements when it was introduced. Running about 10x faster than Oneshot 125, that even made is faster than Oneshot 42 and was the new dream of quad builders everywhere.
Until the developers of Oneshot, Flyduino introduced Dshot that is. Dshot is the first digital protocol produced and had a number of advantages over all of the analog protocols we have talked about. A few notable ones are no longer having to calibrate your ESC’s, the signal being more accurate and less susceptible to electrical noise, a higher resolution or better said a higher number of steps between minimum and maximum throttle. And the ability for the ESC to detect and reject corrupted data.
As far as speed Dshot wasn’t the fastest kid on the block, with Dshot 150 being faster than Oneshot 125 but not Oneshot 42, and Dshot 300 & 600 being faster than Oneshot 42, but not faster than Multishot. However, with all the advancements of a digital vs an analog signal, most pilots would still choose Dshot capable hardware when making new purchases.
An interesting point is that all of this advancement has taken place in the last 2 years, and even now Dshot 1200 is being released that is faster than multishot by a large margin, although with very high hardware requirements as well. So 2 years from now it is impossible to say what we will see available then, or even how much of a difference more speed is going to make from what is already available now.
So does this mean you should go run out and buy some fancy 32bit ESCs running Dshot1200 and a capable flight controller to match? Probably not. If your still flying something with PWM then I would try to get into Oneshot at least. Other than that, I still have some craft using Oneshot 125 that I fly just fine. And it really becomes a question of skill vs budget as well.