General New Stuff

[Airbrush dude]

Hi guys, I've been out of the hobby for about 8ish years. I'm having a hassle getting my head around the new tech. I just got an Frsky XM+ sbus rx, how is this an rx, there is one port to plug into. I'm not getting it, this is a 16 channel rx that plugs into another rx? Um, hu? Feelin kinda stupid, help.

 

[Tony]

That Rx you will need something, like a quad flight controller, that can understand the sbus signal that is coming out of the receiver and going to the model. I just did some checking, and the ONLY thing that I can find on the 3GX that says SBus is for Futaba. If you have a full receiver, try plugging that up and see if you can get some lights on the 3GX. If so, then you know you will need to run a full receiver instead of just an sbus receiver.

 

[Airbrush dude]

I really wish they would standardize some of this stuff. I'll try a regular rx and see what happens.

 

[RandyDSok]

The Frsky SBus is compatible with the Futaba SBus protocol... they work identically ( from what I've read ).


The "old school" method of connecting a receiver to the flight controller ( FC ) required a cable per channel going to the FC and then you'd connect your servos to the FC. With SBus and a FC that supports breaking out to the SBus or standard servos.... you only have a single cable from the receiver to the FC making the wiring much cleaner.

There are hubs available that can split out separate connections for additional servos also... as well as a "convertor" type that allows use of standard servos instead of requiring SBus servos.

 

[Airbrush dude]

Rdsok, I have no clue what you just said. So this sbus stuff is only for quads and stuff?
If I wanna use it in an airplane or heli I still need a receiver?

 

[RandyDSok]

Rdsok, I have no clue what you just said. So this sbus stuff is only for quads and stuff?
If I wanna use it in an airplane or heli I still need a receiver?

No... not what I said... although it's used a lot in multirotors and heli's... it's also used in airplanes and such. For a moment, let's forget about the old analog stuff and for now.. also the flight controllers ... I'll touch on those later.

Lets start the discussion technically correct ( I'll start there and then try to use an analogy to simply and explain it )... SBus is a digital serial interface that allows up to 16 channels in a single line. The SBus servos are programmed ( set ) to their assigned channel so they know which input channel to pay attention to.

A modern computer analogy would be something like a USB hub that you plug into a single port on your computer but can plug many other USB devices into. Of course with a USB hub we'd be plugging in printers, hard drives, flash drives etc... On SBus it'd be servos, motor controllers and the like.

Here is a simple short SBus hub with 3 ports for servos or other SBus hubs etc...

Here is an example setup on a large scale airplane using just the SBus hubs ... Notice how the single line goes to the first hub and is then connected to other hubs that having either servos and/or hubs attached to them. Now for a moment, imagine the mess of wires that would need strung back to the receiver if this was setup using the old style receiver and servos.

Now... let's switch up and talk about using standard servos with a convertor that is similar to what the hub does but for PWM servos ( analog or digital )... here is such a hub that supports up to 16 channels for standard servos

Now to touch on flight controllers... Some of them can do the same as the last SBus hub to PWM servo adapter I posted last... Some work with just SBus servos and some a combination of them... What a particular flight controller supports will vary by which model you are talking/looking at... so you'd need to know which type you'd need first.

Some Sbus type receivers have options to support both SBus as well as PWM servos. Of course they'll be much larger than the one you've got since they'd need pinouts for the standard ( old school ) servos also.


So SBus can be used with any type of airframe. It can simplify the wiring in many cases and I suspect it's going to be the next standard that most all controllers will be using.

 

[Airbrush dude]

Wow rdsoc, thank you for the detailed explanation. I swear my small brain is beginning to atrophy and I'm only 50. I'm barely getting my head around this stuff. Looking at that diagram I'm thinking the frsky XM+ is just for quads because it has only one place to plug something in.

 

[RandyDSok]

Wow rdsoc, thank you for the detailed explanation. I swear my small brain is beginning to atrophy and I'm only 50. I'm barely getting my head around this stuff. Looking at that diagram I'm thinking the frsky XM+ is just for quads because it has only one place to plug something in.

Yeah, you're still not getting it...

So you plug a SBus hub into that one location... you get anywhere from 3 to 16 additional places to plug things in depending on the hub selected and the type of connections that hub provides... Look at the example airplane, it has only one connection going to the receiver and then branches out to several hubs and servos. So it's not just for quads... can be used on other multirotors ( there are more than just quads in that category ), heli's and airplanes.

Chew on that for a bit... if you still don't get it, perhaps someone else can word it in a fashion that you'd better understand

 

[Airbrush dude]

OK I get it now , I went shopping for sbus decoders. To me it seems like they took a standard Rx and separated it's parts. The Rx does just that receives the signal, then you need to plug something else into it to get that signal out decoder/hubs. Instead of Y harnesses they have hubs. Thanks again rdsoc, the explanation was good my brain was just not working properly.

 

[Smoggie]

If you are using the receiver on a flybarless heli then you don't need any decoder or anything else to plug the servos into. The Tx connects to the flybarless controller by the single sbus wire and the servos all connect to the flybarless controller..... Simple.

 

[RandyDSok]

If you are using the receiver on a flybarless heli then you don't need any decoder or anything else to plug the servos into. The Tx connects to the flybarless controller by the single sbus wire and the servos all connect to the flybarless controller..... Simple.

Then an obvious next question ... for the uninitiated ( since I only fly planes )

What type of servos are being connected to the flybarless controller... standard analog/digital ones or sbus... or any of the 3 types?

 

[Smoggie]

You use 'normal' servos preferably digital but analog will work.

 

[Airbrush dude]

I wish every one made an FBL so it could be the rx. I know some do some don't. I think jr will work with the 3GX,
just plug in some satalites. Or is it spektrum , you know what I mean. Just getting back into this hobby it feels like by time your done you have 47 things plugged in.

 

[Tony]

I know how you feel! And yes, Spektrum or JR, as long as they are DSM2 or DSMX satellites, they plug right in. And if you only use one, plug it into port 2. Want some more confusing information? If you run just satellites, the tail gyro gain channel is 7. If you run a separate receiver, it's on channel 5.... I have no idea why they did it that way lmao.

 

[Airbrush dude]

They are messin with us old dudes, there is an engineer somewhere laughing like a hyena .

 

[Tony]

lol, more than likely, you are correct! I say go BX and call it a day. Ikon if you want stability and rescue mode without having to spend over a bill more.