The new Futaba S.BUS

WHAT'S THE REAL MOTIVE BEHIND THIS MOVE?

Dated: 29 Mar 2010

It appears that Futaba has decided to change one of the oldest and most venerable of all RC system standards -- the humble servo interface.

The basic electrical interface presented by the servos we use has remained virtually unchanged for decades, probably because it works just fine for almost everyone.

The only RC fliers who've really welcomed a small change are heli-fliers that demand absolute minimum latency for their tail-rotor servos. Even with their ultra-fast gyro-driven digital servos, the only change to the basic standard has been to increase the frequency that the servo data is delivered.

But now Futaba claims it has created a new method that (to use their words) "is nothing short of revolutionary".

Yes, it is revolutionary, but I'm picking that the reason for this change involves more about what's best for Futaba rather than what's best for the customer.

One Cable To Rule Them All

LOOK, IT'S JUST LIKE A COMPUTER LAN

The concept behind the S.BUS, as Futaba have labeled their new technology, is to do-away with a multitude of individual connections between your servos and your receiver.

By using technology that is somewhat similar to a computer LAN, servos can effectively all be wired in parallel so that instead of running multiple extensions into your wings (for instance) in order to control ailerons, flaps and even air brakes, a single extension can control the different servos that perform these functions.

Likewise, if you have several servos in the tail of your model, the S.BUS would allow just a single extension to deliver the power and signals to those servos.

Sounds like a grand plan, doesn't it?

More information about the S.Bus can be found on page 14 of this PDF file downloadable from the Hobbico website.

Now call me a skeptic but I'm not so sure this is a great concept for anyone, except Futaba's accountants.

Clearly, with the advent of 2.4GHz, Futaba has realized the huge financial benefits that come from locking customers into the Futaba brand. Those who have purchased the very good Futaba FASST 2.4GHz radios will have found that the only receivers that will work with their radios, are Futaba's own very expensive ones.

As the Chinese have shown us, the cost-price of an 8-channel receiver is probably around the US$10 mark, and Futaba's receivers would cost very little more than this to manufacture.

So how does Futaba get away with charging $140 for their 8-channel FASST receiver?

Simple -- they are the only company (right now) that makes FASST-compatible receivers so they know customers will just have to pay whatever is asked of them in order to get one.

So, could it be that this attempt by Futaba to move away from the industry standard 3-wire servo interface to a bus-based system of their own proprietary design just another attempt to tie customers down and reduce competition from other manufacturers?

In a year or so, will Futaba only sell S.BUS-style receivers and thus force their customers to purchase only genuine Futaba servos?

Call me an old cynic, but I would not be surprised if this was the case.

But hang on, surely this S.BUS is simply a great idea and something that's long overdue in an era of computerized radios and digital servos? Well let's look at the pro's and con's of Futaba's S.BUS, based on the information that's available...

Why not S.BUS?

IS IT REALLY BETTER?

In theory, running a single cable instead of multiple extensions sounds like a good idea but there are some drawbacks...

Firstly, the bus-cable must be heavy enough to support the current demands of all the servos that will be attached to it. This means that instead of using three extensions, each capable of delivering 5A, a much heavier extension with 15A capability must be used.

This extra current-carrying capability is even more important where the S.BUS cable connects to the receiver, since a large model (such as a 40% gaser) may have as many as 10 hi-torque servos and their combined current-draw could easily exceed 20A or 30A. Connectors capable of this kind of power are neither light nor small (yet, according to the pictures in the Hobbico catalog, standard servo connectors are used which typically are not rated for more than 5 amps). Not good, not good at all.

Secondly, although the implication of S.Bus is that there is reduced complexity, this isn't really the improvement you might think.

Although the number of extensions is reduced, there is a need for multiple "hubs" to be used to provide the fan-out to the servos.

Also, in order to use a servo in a particular role, it must be programmed with the required channel number. This means customers will need to purchase the "Channel Setting Tool".

It appears that, at least initially, Futaba plans to offer smart hubs that they call an "S.BUS decoder". This (it would appear) will allow the use of existing non-S.BUS servos in conjunction with an S.BUS receiver. However, Don't expect this little box to be on the market very long. It's clearly a tool designed to make the transition to the new S.BUS receivers a little less painless but, once you're hooked, it makes no economic sense for Futaba to keep selling this device -- instead, customers will be forced to buy S.BUS servos (only available from Futaba of course).

The Start of a Trend?

THE END OF INDUSTRY STANDARDS?

This is a risky move on the part of Futaba but one that could enable them to maintain a vise-like grip on the wallets of their customers.

However, those who can cast their minds back a few years will recall that IBM (who used to be "the" standard for personal computers, once tried exactly the same tactic of moving away from the industry standard ISA bus and locking customers into their "new and better" Microchannel Architecture (MCA) bus.

What should have been a clever way for IBM to lock out the clone-makers ended up backfiring badly, as the market said "we don't need MCA, we're happy with ISA -- and virtually stopped buying IBM PCs in favour the clones which offered more choice and better pricing.

Unless JR/Spektrum, Airtronics, Hitec and others also decide to develop their own proprietary servo buses, Futaba risks simply driving customers away through this extension of its current "lock-in" tactics with FASST.

However, if the other "brand-name" players see this as an opportunity to try and go one-better (as has been the case with the whole 2.4GHz market) then incompatibility will reign and prices will skyrocket, as each brand extorts even greater profits from their captive customer-base.

Or, it might just be that savvy modelers will turn away from those who seek to impose expensive new proprietary technologies on them and instead, do what IBM's customers did in the late 1980s -- stick with the status quo in order to save a lot of money and preserve their freedom of choice.

What do you think?

Will you jump on Futaba's S.BUS, or in doing so, are you simply going to be spending more money and being forever locked in to their branded products?

Please tell me!

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