5th Channel with S.Bus2

[trxrdr17]

Hi All,

New to the forum and the crawler world. However, just re-introduction back into the surface R/C community. With that being said, a lot has changed for the better for R/Cs as technology grows.

My question: I have a Futaba 4PV and R304SB that I'm using as my primary TX/RX for all my R/Cs (in my signature). The TRX4 currently needs 5 channels to operate all the features on my rig. The 5 channels are steering, ESC, front diff, rear diff, and 2 speed transmission. I've read into the S.Bus2 protocol that Futaba developed to extend the ability of the RX. I couldn't find any clear indication from my research thus far regarding the implementation to servos outside of the S.Bus2 ready servos. I was hoping to use the S.Bus port to control the 2 speed transmission on my rig. Am I missing something, or is my intention to get another channel out of the TX/RX not possible?

Thanks

[Greatscott]

Can't answer the question about the radio itself, but you only four channels to run the truck.

If you get a Traxxas T-Loc module, you can run the diff lock servos off of one channel.

[Panther6834]

I recently had that same question...although, for a different reason...so, I called Futaba USA. The short answer is, NO, it does NOT increase the channels...at least, with the Rx you're using. However, this doesn't mean there aren't any Futaba receivers capable of "expanding" the number of channels.

The first thing anyone needs to know about S.bus (including S.bus2) is, it can ONLY be used with Futaba's & MKS's S.bus-compatible servos. Not all Futaba servos are S.bus-compatible, and other brands can't be used at all. This is because S.bus-compatible servos contain a microchip that the user needs to program, either by connecting to a computer (with appropriate software), Futaba programming card, or compatible Tx (only the 7PX & 4PM, but don't quote me on the 4PM). The user programs the channel into the servo so that multiple servos (via a Futaba S.bus hub) can be plugged into the S.bus port on the Rx.

Getting back to your Rx, and why it wouldn't work, all 300-series receivers are 'telemetry' receivers, meaning that they're capable of bi-directional data. While you're transmitting control data to the Rx, via up to the 4 primary channels, the Rx can use unused channels to transmit telemetry data to the Tx. Obviously, this requires the use of a telemetry-capable Tx (only Futaba's high-end, and certain mid-range, surface & air transmitters have this ability). This relates to Futaba's Tx/Rx transmission protocols.

Like other manufacturers, Futaba relies on several transmission protocols - FHSS, S-FHSS, T-FHSS, T-FHSS Air, FASST, T-FHSS SR & FASSTest. T-FHSS (which all 300-series fall under) & T-FHSS SR receivers are essentially "locked" into only 4 'receive' channels. I'm not certain about T-FHSS Air receivers, but they might be the same. As it was described to me by a Futaba tech, only the other protocols have the ability to "expand" the number of receive channels (FASSTest can receive up to 18 channels). Obviously, in order to "expand" the number of receive channels, you have to use an appropriate servo...but, you also have to use a Rx that supports that protocol (for example, only air transmitters support the T-FHSS Air, FASST & FASSTest protocols).

So...yes, you CAN use the S.bus to "expand" the number of channels, but NOT using the R304SB you're planning on using, and ONLY if you use S.bus-compatible servos. Only FHSS & S-FHSS receivers can be used...as long as your Rx supports the protocol.

~ More peace, love, laughter & kindness would make the world a MUCH better place

[trxrdr17]

Sooo, I answered yesterday before another post. This reply didn't show up and the other did?

Greatscott - Thanks for the info! Do you have any experience with or own a T-Lock? I'd be curious to know if the PWM servo signal is just being buffered and split or inverted to one of the two servos.

Panther6834 - Thanks for sharing about your Futaba tech support inquiry, a wealth of knowledge! I was hoping the S.Bus port on the R304SB had dual functionality as traditional digital PWM servo port. I believe the programming card/software you mention is assigning addresses to the servos that would be connected to the S.Bus (I'm guessing S.Bus stands for serial bus?). With any communications bus, it's important to implement addressing when 2 or more 'nodes" are present. This way every "node" knows who's talking to who. It also makes sense to me that an telemetry data would be passed on the S.Bus. I wonder if anyone has hacked one...

[trxrdr17]

For those interested, I reached out to Traxxas tech support and they told me I could basically connect the servos together and run them in parallel from the RX. If if wanted to use the T-Lock, they couldn't guarantee it would work and I would need a 3 way switch on my TX.

[Panther6834]

Originally Posted by trxrdr17

For those interested, I reached out to Traxxas tech support and they told me I could basically connect the servos together and run them in parallel from the RX. If if wanted to use the T-Lock, they couldn't guarantee it would work and I would need a 3 way switch on my TX.

You could just buy a 6-channel Rx. The Futaba R2006GS is an excellent option. Although originally intended for Air/Heli, it's used with frequently by crawlers, and should be compatible with all Futaba surface Tx. I'm using one in my first Capra, with all 6 channels in use (steering, throttle, dig servo, and 2 lighting channels).

~ More peace, love, laughter & kindness would make the world a MUCH better place

[trxrdr17]

Panther6834 -Do know if that with the 4PV TX? Would I just implement servo mixing or something?

[Panther6834]

Originally Posted by trxrdr17

Panther6834 -Do know if that with the 4PV TX? Would I just implement servo mixing or something?

If you're using it to operate the diff lock & trans servos, and all three switches will be set as 2-position (off & on), you'd essentially program the Tx similar to lighting. The "off" would hold the servo centered (you'd need to install the arm into the servo with the 'switch' in the off position), and the "on" would move the servo to the other position. For example, for the locking diffs, "off" would be whichever you'll normally use (I'd assume 'unlocked'), and "on" would be the opposite (ie, 'locked'). For the trans, "off" would be 1st gear, and "on" would be 2nd gear. For all three, you'd need to initially set the end point REALLY low...then, once operational, you start increasing the endpoint until that servo 'engages' the switch.

~ More peace, love, laughter & kindness would make the world a MUCH better place