Reverse engineering a Futaba SBUS remote control

April 5, 2012 By Leave a Comment

In the world of model aircraft, Futaba’s SBUS system is a big deal. Instead of having one servo per channel, the SBUS system allows for 16 proportional controls and two digital channels for each receiver. Basically, if you’re building an awesome plane with retracts on the landing gear and bomb bay doors, this is what you want to use. [Michael] wanted to use a few SBUS servos for a project he’s working on, so of course he had to reverse engineer this proprietary protocol.

Each SBUS servo operates over a single 100kbps serial connection with a few interesting twists: the signal is transmitted as big endian, but the individual bytes are little endian, something [Michael] figured out after stumbling across this month old mbed post. [Michael] used a serial library written by [fat16lib] and was able to change the parity and stop bits along with a simple hex inverter. Everything worked perfectly when the servo was connected to a an Arduino Mini.

Even though the SBUS system requires special Futaba servos, we can easily see how useful [Michael]’s work would be to outrageously complex robots or cnc machines. Check out the video after the break for a quick demo of [Michael]’s breadboard controlling one of these SBUS servos.

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Building a combination lock with logic chips

March 30, 2012 By Leave a Comment

The component gods must have smiled on [Darrell], because he recently ran into a cabinet full of 7400-series logic chips for sale at his local college surplus. All the regulars were there – flip-flops, logic gates, and SRAMs – in DIP packages. the 7400-series of logic chips gets very esoteric as the numbers increased, so when [Darrell] found a 74ALS679 address comparator, he didn’t quite realize what he had. After a quick review of the relevant datasheet he had a fairly good idea of the actual function of this chip and decided to make a combination lock.

From the datasheet, [Darrell] figured out how this small logic chip can compare two 12-bit addresses with only 20 pins: each of the 12 address pins are hardwired to match a single four-bit value. If the four-bit ‘key’ is set to 0110, the first six address pins are tied low, and pins 7-12 are tied high. After wiring up his address comparator to a trio of Hex dip switches, [Darrell] had a combination lock that used the word ‘FAB’ as a key.

In the 7400-series of logic chips, there are some oddballs; the 7447 seven-segment display driver is useful, but the 74881 ALU and 74361 bubble memory timing generator aren’t exactly something you would find in a random component stash. If you’ve got a weird logic chip build (there’s a 300-baud modem, you know), send it on in. You can check out an animated gif of [Darrell]’s lock after the break.

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Press play on tape for your Fignition

March 26, 2012 By Leave a Comment

[Julian Skidmore] has been busy improving the Fignition, a tiny AVR-powered educational computer, to support loading programs from a cassette tape.

We first saw the Fignition after the BBC decided to cover an old-school hacker dedicated to improving computer education with a simple ‘bare-metal’ computer. [Julian]’s Fignition harkens back to the days of very simple computers like the BBC Micro and the TRS-80, and encourages students to work with PEEKs and POKEs instead of the decades of cruft that have accumulated on our laptops and desktops.

Because the Fignition is designed to hacker and student-friendly, it’s entirely possible to build a keyboard, or even build a Fignition on stripboard. Now, these students have much improved hardware that allows for saving and loading programs to tape (or any audio recorder) , and even a graphic video mode with 160×160 resolution.

We know it seems a little weird, but kids graduating High School this year were born in 1994, and in all probability have never laid their eyes on a Commodore 64, Sinclair Spectrum, or the other 1980s microcomputers an entire generation learned on. The Fignition is an attempt to stem the tide of ignorant masses unaware of how far the computer has progressed in the last 30 years, and we love it for that.

Filed Under: classic hacks, hardware Tagged With:

SimpleCortex, for when an Arduino is too wimpy

March 25, 2012 By Leave a Comment

Sometimes, an Arduino just doesn’t have enough horsepower. Whether you’re gathering loads of sensor data and sending it over the web via Ethernet, or just trying to build a home-brew video game, it’s very easy to run into the limitations of the Arduino platform. [Rik] and his fellow classmates may have a solution to this problem with their SimpleCortex development board.

The SimpleCortex began as an answer to the Arduinos [Rik] and his classmates had to use at school.  The SimpleCortex gets its name from an ARM Cortex M3 microcontroller running at 120MHz; more than fast enough to do some very interesting things, and 512kB of Flash to hold much larger programs.

The Arduino IDE is admittedly terrible, and big projects are a pain in the butt with a tiny 8-bit micro. SimpleCortex improves upon this development environment by using the free CoCenter IDE put out by CooCox. The CoCenter IDE supports debugging and code completion, standard features on any serious desktop programming environment.

The SimpleCortex has Arduino-compatable header pins, so it should be easy to use existing shields, like the 3G modem we saw this week and the NTSC video IO shield that can do object tracking. While the specs of the SimpleCortex put it in a distant second to the Raspberry Pi, sometimes you just don’t need Linux, but a standard AVR or PIC isn’t quite enough.

There’s no word on when this board will be available, but the team is working with ITead Studio to officially release boards into the wild.

Filed Under: hardware Tagged With: ,

Self-stabilizing autonomous bicycle

March 25, 2012 By Leave a Comment

For [Gunnar]’s diploma thesis, he wanted to build an autonomous bicycle. There’s an obvious problem with this idea, though: how, exactly does a robotic bicycle stand upright? His solution to balancing the bicycle was a reaction wheel that keeps the bicycle upright at all times.

A bicycle is basically an inverted pendulum; something we’ve seen controlled in a number of projects. To balance his driver-less bike, [Gunnar] used a stabilizing wheel and an IMU to make sure the bicycle is always in the upright position. The bike measure the tilt and angular velocity of itself, along with the speed of the stabilizing wheel. To correct a tilt to the left, the stabilizing wheel spins clockwise, and corrects a rightward tilt by spinning counterclockwise.

While [Gunnar]’s solution of a bike wheel used as a gyroscope is clever – it uses common bicycle wheel, hugely reducing costs if someone wants to replicate this project – there’s not a whole lot of ground clearance. The size of the stabilizing wheel could probably be reduced by replacing the 7.4 kg steel wheel with a Tungsten, Osmium, or Lead disk, possibly becoming so small it could fit inside the frame. Still, though, a very nice build that is sure to turn a few heads.

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Filed Under: hardware, robots hacks Tagged With: , ,

The first Raspberry Pi build is a MAME machine

March 22, 2012 By Leave a Comment

The Raspberry Pi was launched nearly a month ago, but these wonderful cheap single-board computers are still on their way from China to the workbenches of hackers and builders around the globe. Although they haven’t shipped yet, plenty of people are chomping at the bit to do something useful with the Raspi. [Nicholas] figured he should hit the ground running, so he emulated a Raspberry Pi to get everything ready for the MAME machine he’ll build when his new toy arrives.

[Nick] found a Raspi VirtualBox image on the official Raspberry Pi forums. After getting a web browser up and running with a few console keystrokes, he turned his attention to a MAME emulator. It’s a relatively simple install (although it did take six hours to compile), but we’re sure the Raspi will be featured in quite a few MAME builds so it was time well spent.

Sure, the Raspberry Pi you ordered a month ago is probably on a container ship in the middle of the ocean right now, but that doesn’t mean you can’t start planning your build. Just load up a VirtualBox image, check out a few of the tutorials, and you’re ready to go.

Filed Under: hardware, linux hacks, Rasberry pi Tagged With: , ,
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