An Open Source 1MHz Arbitrary Waveform Generator With An Awesome UI

August 9, 2014 by Mathieu Stephan 15 Comments

[Herp] just shared a nice 1MHz Arbitrary Waveform Generator (right click -> translate to English as google translation links don’t work) with a well designed user interface. His platform is based around a PIC32, a TFT module with its touchscreen and the 75MHz AD9834 Direct Digital Synthesizer (DDS). Of course the latter could generate signals with frequencies up to 37.5MHz… but that’s only if two output points are good enough for you.

As you can see in the video embedded below, the ‘tiny dds’ can generate many different kinds of periodic signals and even ones that are directly drawn on the touchscreen. The offset and signal amplitude can be adjusted using several operational amplifiers after the DDS ouput and a separate SMA TTL output is available to use a PIC32 PWM signal. The platform can read WAV audio files stored on microSD cards and also has an analog input for signal monitoring. Follow us after the break for the video.

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DEFCON 22: Badge Talk

August 8, 2014 by Mike Szczys 21 Comments

I got a great seat on the main floor for the first big DEFCON 22 talk which is a welcome to the con and discussion of the badge hardware. [LosT], the creator of this year’s badge, started the discussion with a teaser about the badge… there’s a phone number hidden as part of the challenge. [LosT] took a call from someone chasing the puzzles. The guy was in the audience which was pretty fun.

The process of building a puzzle that can be solved at DEFCON is really tough. How do you make it just hard enough that it won’t get pwned right away but easy enough that a large number of attendees will be able to figure it out during the weekend? The answer is to build a secure system and introduce strategic flaws which will be the attack vectors for the attendees solving the badge challenge.

defcon22-badge-cut-traces-to-remove-components

Of course the badge can be used as a development platform. The populated electronics on the board all have these nice little footprints which can be cut to disconnect them from the chip. The breakout headers on either side of the board allow you to connect headers for your own uses. Great idea!

The back of the lanyards have special characters on them too. This encourages community at the conference. To solve the puzzle you need to find others with different lanyards. Compare the glyphs and crack the code (so far I have no clue!!).

Know what I’m doing wrong? Have suggestions on where to go from here? I’ll be checking the comments!

San Francisco Event: Hardware Developers Didactic Galactic

August 6, 2014 by Mike Szczys 8 Comments

It’s a mouthful to say, but an evening-ful of fun. San Franciscans who like to talk about all things hardware need to block this one out on their calendars:

Hardware Developers Didactic Galactic
Thursday, August 14th 2014 starting 6pm-9:30pm
500 3rd St., Suite 230 in San Francisco

The night will include a few talks on hardware; So far we know [Matt Berggren] is doing FPGA stuff, [Chris Gammell] will talk about KiCAD, and I’m going to talk about the community adventure that is Mooltipass. We’re also looking for others to make presentations so step up and share your hardware passion!

In addition to the formal talks there’ll be plenty of time for chewing the fat with all the other hardware-awesomes that will be there. See you a week from tomorrow, and don’t be shy about bringing your own hardware to show off!

An Excel Based High Frequency Transistor Amplifier Calculator

July 31, 2014 by Mathieu Stephan 6 Comments

[Paulo] just tipped us about an Excel based high frequency transistor amplifier calculator he made. We’re guessing that some of our readers already are familiar with these class A amplifiers, commonly used to amplify small audio signals. Skipping over the fact that their efficiency is quite low — they are cheap to make, don’t require many components and usually are a great way to introduce transistors to new electronics enthusiasts. All you usually need to do is a few calculations to properly set your output signals and you’re good to go.

Things are however more complex when you are amplifying 200MHz+ signals, as all the components (complex) impedances have to be taken into account so you can get a nice amplification system. On a side note, at these frequencies your transmission lines impedances may even vary depending on how much solder and flux you left on your SMT pads along the way. [Paulo]’s calculator will therefore compute most of the characteristics of two class A common emitter/collector amplifiers for specified loads.

Changing Unipolar Steppers To Bipolar

July 29, 2014 by Brian Benchoff 68 Comments

If you’ve been a good little hacker and have been tearing apart old printers like you’re supposed to, you’ve probably run across more than a few stepper motors. These motors come in a variety of flavors, from the four-wire deals you find in 3D printer builds, to motors with five or six wires. Unipolar motors – the ones with more than four wires – are easier to control, but are severely limited in generating torque. Luckily, you can use any unipolar motor as a more efficient bipolar motor with a simple xacto knife modification.

The extra wires in a unipolar motor are taps for each of the coils. Simply ignoring these wires and using the two coils independently makes the motor more efficient at generating torque.

[Jangeox] did a little experiment in taking a unipolar motor, cutting the trace to the coil taps, and measuring the before and after torque. The results are impressive: as a unipolar motor, the motor has about 380 gcm of torque. In bipolar mode, the same motor has 800 gcm of torque. You can check that video out below.

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An Automated Flappy Bird Player

July 27, 2014 by Brian Benchoff 30 Comments

game Flappy Bird has been ported to just about every system imaginable, including but not limited to the Apple II, Commodores, pretty much every version of the Atari, and serves as a really great demonstration of the TI-99’s graphics capabilities. Porting is one thing, but having a computer automate Flappy Bird is another thing entirely. [Ankur], [Sai], and [Ackerly] in [Dr. Bruce Land]’s advanced microcontroller design class at Cornell have done just that. They’re playing Flappy Bird with a camera, FPGA, and a penny wired up to a GPIO pin to guide the little 8-bit-bird through Mario pipes.

The setup the team is using consists of a webcam that records the screen of a smartphone, an FPGA, and a little bit of circuitry to emulate screen taps. Inside the FPGA, the team is looking at the video stream from the phone to detect the bird, pipes, and gaps. The ‘tapper’ unit is a US penny, placed right above the ‘tap’ button, wired to a GPIO port. This was found to be the ideal contact for a capacitive touch screen – taps that were too small weren’t registered, and taps that were too big registered as two taps.

For spending an entire semester on automating Flappy Bird, the team has a lot of knowledge to show for it, but not the high score: the bird only makes it through the first pipe 10% of the time, and the second pipe 1% of the time. The high score is three. That’s alright – getting the algorithm right to play the game correctly was very, very difficult, and to nail that problem down, they estimate it would take at least another semester.