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Futaba SBUS best practises

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Old 06-05-2017, 03:44 PM
  #1
PeterP
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Default Futaba SBUS best practises

I have been trying to get some information from the Futaba support forum and cant seem to get an answer for my question.

I am in the process of setting up a new F3A model using Futaba SBUS-2 all round. I am also using the Futaba RS7008 receiver which has a SBUS port and a SBUS-2 port.
I am also using the Futaba GPS module and a Jlog32 interface which converts Jeti-EX protocol to Futaba Fastest protocol for my Jeti MEZON ESC. I also know that all telemetry enabled devices need to plug into my SBUS-2 port for Bi-directional dataflow.
I also know that my SBUS-2 servos will work in either SBUS ports on the RS7008 receiver. My question is do I connect everything to the single SBUS-2 port on the receiver or do I share the data load across the SBUS ports knowing all my servos will work on either port. I am not concerned with power load as this is all on the same bus but simply trying to understand what happens inside the receiver when processing SBUS data. Does the receiver give priority to a particular SBUS port. Is it good practice to place all flight control devices (i.e. servo's) on a different SBUS port to telemetry devices if you have the choice. Does the receiver microcontroller use multiple serial ports for SBUS data or is the data from both SBUS ports multiplexed to a single serial communications port.
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Old 06-06-2017, 02:42 AM
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bem
 
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Hi,
I doubt You will have negative effect on anything if You connect everything to S-BUS2.
But if in doubt use the normal S.BUS for the servos and all telemetry devices on S-BUS2.

I use on my F3A plane everything connected to S.BUS2 only and it works fine.
I have only one telemetry device, a current sensor.
I have used this setup since last season.
Oxai Galactika unboxing, assembly, setup, maiden etc.

/Bo
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Old 06-06-2017, 09:05 AM
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I have one caution about using only one connection to your receiver. I lost an almost new pattern plane due to a loss of radio, after extensive analysis we came to the conclusion that the cause was most likely the single connection to the receiver, We assume it came disconnected in flight, causing servos to go to fail-safe lock in current position. Loosing one servo you can sometimes survive, loosing them all, you don't

I now make 2 connections and use a hub to inter-connect the two sides.
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Old 06-10-2017, 09:52 AM
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I would connect the servos to the SBUS port and telemetry devices to SBUS2 port. The reasoning behind is to avoid a single point of failure, just like Bill recommends above. Additionally, what if one of the telemetry devices goes completely haywire and floods the port? In this case separating the connections helps too. Of course the bad scenarios are unlikely but since you have the option to use two ports, there's no reason not to do it.
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Old 06-17-2017, 11:25 AM
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Peter,

I use S.Bus2 on my F3A byplane, it has 9 channels, this is how I did it.

The system is all HV, the higher the voltage, the lower the Amps used by the servos, so even better on single connections.
The two elevator servos have a soldered Y connection at the tail, so one connector at the front
Each wing two servos, soldered wires to one connector, then a Y harness for both wings
Then a hub connects, the connector for the two wings and the two elevator servos, all this to the S.Bus2 port on the RX 7008
Throttle servo to a regular Rx port
300oz Rudder servo to a regular port
An Emcotec electronic SW to a regular port

So, S.Bus2 servos recognize the type of signal, being regular channel or S.Bus, so on power up, each servo recognizes the type of connection and operates accordingly.
The rudder servo does not have any benefit in my case as the servo is at the wing area from using the S.Bus2, so it goes to a separate channel and it is the most powerful servo so not all the power goes thru the same connection.
The throttle, same as the rudder as it is closed to the Rx does not benefits from the S.Bus2, so direct connected.
The electronic SW is analog, so it needs a regular port.

So, summarizing,

You do not need to have everything on the S.Bus2, even though all your servos are S.Bus2.
You can combine or connect each function wherever you want, but the Telemetry which has to go to the S.Bus2.
The amount of sensors do not slow down the system that much, what does is the sampling rate, so do not use the fastest, or faster than really necessary.
Yes, the Futaba page and instructions sucks really bad, I had to come up with this on my own.
You can use S.Bus2, Digital and analog servos all together if you want, of course, same type of voltage, and same type of servos on the same control surface, hope not insulting, but I have seen things........

I hope this helps.

Last edited by apereira; 06-17-2017 at 11:28 AM.
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Old 06-17-2017, 09:42 PM
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Thanks for the replies all. I am going to separate telemetry and servos for my setup on the assumption that both SBUS ports work independently to each other.
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Old 06-18-2017, 02:40 AM
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Peter,

There is only one S.Bus2 port.

S.bus servos will work as regular servos on any other port.

Regards
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