The FrSky Telemetry Project

Your Reviewer

My Credentials
So who's doing this reviewing then?

Well I've been building and flying or driving radio controlled models for over 40 years and during that time I like to think I've built up a reasonable amount of knowledge.

I'm also a qualified electronics engineer who has worked in radio frequency, analog, digital systems and software for more than three decades. In fact I designed and built my first RC set back in 1969.

For the past nine years I've also been involved in the design and manufacture of some rather sophisticated engine technology and UAV flight control systems.

So, chances are I've been there, done that and have a huge pile of tee shirts to prove it.

Right now I'm heavily into 3D flying and enjoy all aspects of the RC hobby. I may be old but I don't feel it.

In the Pipeline

Here's just a little bit of what's to come on this site...

RC explained: Demystifying terms such as PCM, PPM dual conversion, single conversion, full-range etc., this feature will explain it all.

Cheap Chinese Engines: Just how good are those cheap Chinese glow and gas engines that sell for half the price of their "brand-name" equivalent? I put several to the test.

Build your own radio gear?: Back in the old days, building your own RC gear was not uncommon and now the arrival of 2.4GHz has made it practical again.

DIY: The FrSky Telemetry Project

BUILD IT YOURSELF

Updated: 18 Oct 2010

Time for an update -- here are some pictures of the (very) prototype telemetry hub and the speech synth board for the dashboard.

Don't worry about the surface-mount processor -- I used this because I've got dozens of them. If people want through-hole versions I'll change the layout to accommodate the through-hole equivalent.

This board has a connector for the GPS, a general-purpose analog (ADC) and a general-purpose digital input as well as an SPI buss connection for adding extra "smart" sensors as/if required.

The SpeakJet synthesizer is (to be honest) not that good and, at $25 per chip, I'm having second thoughts about how to provide speech capabilities. I'm now looking at using an MP3 chip and allowing people to record their own vocabulary in their own language -- makes it much better for non-English users. What's more, the MP3 chips are cheaper than the SpeakJet ones.

However, the testing will be done with these boards and I'll post video ASAP.

Dated: 8 Jul 2010

I've been quietly slaving away here over a hot soldering iron and software compiler, creating an open-source telemetry dashboard that will work with the recently released 2.4GHz FrSky 2-way telemetry-enabled module/receivers.

Why did I choose FrSky?

Well, as co-winner of the first ever RCModelReviews 2.4GHz shootout, it offers a good combination of low price, features and performance.

And, as a bonus, FrSky have published the communications protocols that make it much easier for independent developers to create products like the system I'll be documenting on these pages.

Unlike Hitec and Spektrum, tapping into the FrSky telemetry system for your own needs is almost trivial, thanks to their "open" attitude to the technology.

A little preview

I'm still tidying up some loose ends at the moment and waiting for the chance to perform the first flight tests but here's a little preview of what you'll be able to do with the first version of the project:

Signon screen

Without receiver turned on

Setting the origin (zeroing alt/position)

Post-flight report (maximums)

Basic Design

The system consists of two components, the dashboard, which plugs into the transmitter module and displays all the telemetry data on an LCD attached to that transmitter, and the airborne telemetry hub which connects an array of sensors to the receiver.

The airborne telemetry hub

The airborne hub communications with a range of sensors such as a GPS module and barometric altitude sensor. The hub also has many unused inputs so you could also connect extra sensors such as accelerometers (to measure G-forces), an air-speed sensor (GPS reports ground-speed), a tachometer for glow/gas engines, current sensor for electrics and fuel-gauge, amongst others.

The airborne hub can accept digital inputs and analog (voltage) inputs so you can measure the voltage of the lipo powering your model's electric motor if you wish. Receiver voltage is automatically detected and reported.

The hub takes all these many inputs and organizes them into a stream of digital data which is then fed into the FrSky 2-way receiver for transmission back to the transmitter module on the ground.

Over coming weeks I will be refining the way in which this is done by adjusting the priority of certain data and adding a greater level of data compression so as to ensure the fastest possible updates to the LCD display on the pilot's transmitter.

The dashboard

Once the stream of data from the airborne telemetry hub reaches the transmitter module and is made available through its data-port, the dashboard system takes over and turns that stream of bits and bytes into a human-readable form.

Right now I'm using a text-based LCD display for simplicity but may modify this to provide a 128x64 graphical display.

The dashboard is interactive and can be programmed to display a range of different data depending on the wants/needs of the user. It's also obviously dependent on what sensors are being used in the aircraft.

Over-value alarms can be set for many parameters such as airspeed, altitude, distance and under-value alarms can be set for battery voltages so as to alert the pilot when the model is operating outside of safe limits. These alarms sound a buzzer in the dashboard with different tones for different conditions. It is my intention to extend this functionality to add speech synthesis and an earplug connection so that all the required information can be reported without the need for the pilot to take their eyes off the model while flying.

Hardware

Because I have quite a bit of experience with the Microchip PIC family of microcontroller chips, I've opted to use these for this project. PIC chips are widely supported and if you want to learn to program them yourself (which you probably don't) there's plenty of tutorial information on the internet.

There is one processor in the dashboard and one in the airborne hub. Fortunately, these are very cheap and readily available.

The bare circuit boards can be made by hand and I'll be outlining the process for those who wish to get "down and dirty" to this level -- otherwise, if there's enough demand, I'll commission a small run from one of the many companies that specialize in the creation of such things and make them available at cost to readers. Others may also choose to make boards and offer them for sale, I guess we'll see what happens there.

The system as it stands has not yet flown and I hope to do this sometime in the next week or so, as fine weather is forecast here (unusual for winter).

At that time I'll post a video to the RCModelReviews YouTube channel showing how the system performs in the air.

Once I'm happy with its performance and that there are no major bugs, I'll publish the circuit diagrams, circuit-board layouts and software here.

In the meantime, you're all welcome to discuss this project in the forums and ask questions or proffer suggestions.