Miniature "stealth" phone GCS, maybe the smallest usable ever...

I promised a while ago that we're going to show you some simpler gear than our high-end client builds or series production stations. Well, this is one of them.
A smartphone and a self-powered snap-on telemetry modem. You may ask what the point is in combining these two things together, especially when the Bluetooth telemetry bridge solution has already been out there for quite a while. Mainly because it's handy, extremely compact and, of course, there are always some reliability issues with other applications, when the BT connection breaks down, as you may as well just walk out of its range.
Since the BT link only has to bridge about an inch of fixed distance here, there's no way any external RFI can break it down, but it still helps maintaining the secure IP67 level waterproof state of both the Sony phone and the modem box. There's nothing to plug in during operation, just snap on the phone, switch on the unit and go.
It is mainly intended for highly autonomous sUAS systems capable of automatic take-off, landing and waypoint based flights, but since the manual controls are already implemented in a couple of Android based GCS sw, there's no reason to limit its usefulness for other applications. It's also a good companion telemetry station for dual operator scenarios, where the manual functions are controlled through FPV by the other crew. While the RFD900 is certainly an overkill for most short range platforms, there's is still the possibility of using it with a digital video downlink, too.
The bridge box is based on a modified RFD900/868 modem with a serial BT module attached to it. We've replaced the heat sink of the modem with a ceramic type, mainly because it was way easier to seal it than the jagged edge of the original one, but it's also more protected like this in a recess. The miniature toggle switch and the charger connector are also waterproof, and they go well together with these stock industrial enclosures.

An intelligent PCM protects the lipos that power the box for a good few hours of battery endurance, depending mainly on the output setting of the RFD modem. However, even running at a full 1W I couldn't deplete them in over six hours. There are two versions presented here in two variants of the same enclosure line. The thicker type makes use of the diversity capabilities of the modem  and it also has a bit more Whs of batteries in there, 15Wh instead of the thinner's 12Wh.
Because I personally hate large smartphones with 5"-5.5" screens, this one is a relatively small 4.6" beauty, making the whole assembly even more compact. If I need a larger display for any application, I'd rather use an 8" tablet instead of a cumbersome phone. BTW, we have also made such snap-in carrier boxes for various 8" Android and Windows tablets for similar applications. I can also create a blog entry about those the next time, if you are interested...

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Comment by MikeRover on February 19, 2017 at 4:42am

Great work!  Any issues getting FCC or other cert for the RFD 900?

Comment by Azjeg on February 19, 2017 at 7:06am

As this is not so much of a commercial product, we don't care, but it could be certified, if needed. I'd rely on Seppo's expertise in this. Straight from the horse's mouth: "The RFD900 is designed to be compliant to AS4268:2012, and FCC 15.247. It has not been certified as a standalone modem and should be compliance tested in the final product." (from the RFD900 datasheet)


Comment by Daniel Agar on February 19, 2017 at 1:03pm

Looks good. Did you consider using USB for the serial connection to the RFD900, possibly powering it as well?

Comment by Olivier on February 19, 2017 at 1:49pm

Very cool. Great work!

Comment by Azjeg on February 19, 2017 at 2:38pm

Daniel,

No, because the point of this simple assembly was exactly to evade a wired connection and not to deplete the phone battery with a high power modem, either.  Both the stock industrial enclosure and the Xperia are perfectly waterproof, why mess it up with a connector and a cable? :-)

While we mostly fly in fair weather, our ArduBoat and ArduRover applications are rarely so lucky, so they do require such waterproof controllers.

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