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After recently getting the D4R-II receiver for my quadcopter I'm ready to call it my favorite I've used or seen. 

Why do you ask? You don't? I'll tell you anyway.

It's "4 channels" but has CPPM (collective PPM) support out of the box for all 8 channels. In other words you'll only need Vcc, Gnd, and CPPM to connect it and get all 8 channels. Software is way simpler with CPPM and you have one of the smallest RX out there.

It's a real telemetry model. Out of the box the FrSky TX will beep when it's going out of range. You can hook up off the shelf 'sensor hub' modules and use expensive LCDs to see telemetry like battery voltage and position. Bleh. My setup uses this telemetry option as a transport layer for arbitrary data sent from MultiWii or ArduPilot directly. It's not high throughput but it is highly useful. More on that in a bit.

It's hackable to use TTL serial logic. FrSky uses RS-232 inverted logic for all telemetry communication. That sucks. They used mosfet transistors as inverters (see this diagram from sparkfun's tutorial). I fixed this inverted logic problem by soldering nice wires to the pins where TTL logic comes off the STM32F103 µC it uses. Now I don't need a level converter on my quadcopter! 

Flying around Tennessee Valley, CA. It's between the Headlands and Muir Beach. 

Music by Larry and His Flask -- Beggars Will Ride

(See this post on diydrones!) Hiking Sweeney Ridge on Thanksgiving morning was a perfect time for testing out my newly completed quadcopter.

The NCSU Aerial Robotics team went out to Dorothea to fly a few weekends ago, and RJ brought his 18 pound 88" wingspan 60cc Extra 300. Add my gopro, some handy ground footage, and a dubstep remix of 'fly like an eagle' and you get this:

This was taken on my friend Hardik's Canon 60D. Music is from the band State Radio and the song: Wicker Plane.

http://itunes.apple.com/us/album/year-of-the-crow/id395632644

I used ffmpeg extensively to get the 60fps video to slow-mo 30fps, then ffmpeg again to extract the audio to wav, then Sound Studio (mac app) to resample the audio to the same speed as the video. Next I used Sound Studio to splice, in rythem, the intro, solo, and final few seconds of 'Wicker Plane' together, then mix it together with the slow-mo sound of my quad and just imovie to put together the timeline of video.

Using an Phillips NXP LPC20148 ARM7 processor, a Nintendo Wii motion+, and some xbees I've made a really stable platform for quads. (mode details here) It is running FreeRTOS which makes it very expandable in the future. My old frame flew great with it, but I wanted something smaller. Enter my new carbon fiber mini-quad:

New video of my flying my quad!

Flying my os-copter quadcopter inside.

See more Photos.
My writeup here.
Browse my Code: on my svn browser.

This semester I built my own open source flight software for quadcopters using the NXP LPC2148 ARM 7 processor on an FreeRTOS system. This allows the inherently unstable quadcopter to fly as a human controllable helicopter with only the addition of a wii motion plus as a gyroscope sensor for rotational acceleration. Also: details and photos of my first remote.

I'm calling this quadcopter design The Crossbow because of the huge number of people who have thought that's what it was while I'm carrying it around campus.

Right now I'm just testing it and working on the software using only two rotors. This design is modular so I can attach whichever arms I want.

Here's an idea for what I started with in the design process:

This is the flight computer module:

And the body with the two arms attatched.

Building any radio controlled vehicle is usually a money intensive endeavor. When you're building one that flies, is computer controlled (and will hopefully soon be autonomous) it goes to reason that it will be extremely expensive. Some quadcopters are literally tens of thousands of dollars because they use electronics like this. For my quadcopter I wanted to keep the cost as low as possible but still create a reliable platform for future development. I started with the aeroquad project and have done a lot of research on diydrones. Here's the spreadsheet I made before ordering everything (thanks google docs):