AVR Chiptune Project Turns This Simple Code Into Music

[Mark] had seen a few examples of algorithmic music generation that takes some simple code and produces complex-sounding results. Apparently it’s possible to pipe the output of code like this directly to audio devices on a Linux box, but [Mark] decided to go a different direction. His project lets you play simple algorithms as audio using AVR microcontrollers.

Now the code work for this is very simple, but he hardware implementation is where things get interesting. Ostensibly, [Mark] didn’t have the components available to build a filter to use PWM as an audio signal. Being that he’s a ham operator, he grabbed some radio equipment he had on hand and whipped up an alternative. He’s feeding the PWM from an Arduino into the voltage controlled oscillator on a board meant for high-altitude balloon telemetry. The signal broadcast by this board is then picked up by his radio receiver, and played on some speakers.

Rube-Goldberg contraptions aside, the effect is pretty interesting, as you can hear in the latter half of the video clip which we’ve embedded after the jump.

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Over-the-air FM Radio Gains Internet Control

[Old bit collector] is giving up control of his radio dial to the Internet. He combined a couple of Parallax products which now allow him to tune, adjust volume, and toggle the power for an FM radio receiver.

The setup is pretty simple. An FM receiver module is mounted in the breadboard seen above which helps to break out its control pins. Those are connected to a Parallax Spinnarette web server board. It’s auxiliary I/O pins are controlled via a web interface that he set up and plans to operate with the browser on his Android phone. But as you can see after the break, any web browser works as long as you know the correct address.

This is pretty good if you’re on a quest to make everything controllable from your smart phone. But we would love to use the concept to make our own streaming radio. You’d be able to tune in to all of your local stations from anywhere in the world.

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Project 25 Digital Radios (law Enforcement Grade) Vulnerable To The IM-ME

Would you believe you can track, and even jam law enforcement radio communications using a pretty pink pager? It turns out the digital radios using the APCO-25 protocol can be jammed using the IM-ME hardware. We’ve seen this ‘toy’ so many times… yet it keeps on surprising us. Or rather, [Travis Goodspeed’s] ability to do amazing stuff with the hardware is what makes us perk up.

Details about this were presented in a paper at the USENIX conference a few weeks ago. Join us after the break where we’ve embedded the thirty-minute talk. There’s a lot of interesting stuff in there. The IM-ME can be used to decode the metadata that starts each radio communication. That means you can track who is talking to whom. But for us the most interesting part was starting at about 15:30 when the presenter, [Matt Blaze], talked about directed jamming that can be used to alter law enforcement behavior. A jammer can be set to only jam encrypted communications. This may prompt an officer to switch off encryption, allowing the attackers to listen in on everything being said to or from that radio.

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Playing SNES With An R/C Controller

Normally when we see an R/C transmitter used in a build we’re prepared for robots, quadcopters, or UAVs. [Alex] found a new use for his Futaba radio – hooking it up to his Super Nintendo.

We’ve seen a lot of builds using game controllers as interfaces to other hardware. The N64 media remote comes to mind, as does the NES iPod dock. Outside of a few builds to automatically win in-game currency for you, we haven’t seen much of anything to control a video game with additional electronics. [Alex]’s build happily bucks that trend, and technically gives the SNES an analog controller.

The build uses an mBed microcontroller to capture the radio’s button and stick positions. This is sent through a two shift registers to produce the 16-bit packet required of the SNES controller protocol. [Alex] posted all the software for his build, and from the looks of it the code seems pretty portable. [Alex] says he’s working on getting his Sega Saturn running with his Futaba, so we can’t wait to see some Panzer Dragoon action. Check out [Alex] demoing his controller with Gradius III after the break.

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[Scott] Made A Single-chip Hellschreiber On Earth

[Scott Harden] is drilling teeth by day and designing radios that send secret messages by night. He’s set his sights on the Hellschreiber protocol which was used by the Germans in World War II along with their Enigma encryption system. The protocol is a viable alternative for transmitting and receiving code in environments with too much background noise for other communication systems.

His goal was to develop his own transmitter using just one microcontroller. He picked an ATmega48 and coupled it with a 40 MHz crystal oscillator. [Scott] mentions that there is no other hardware necessary, but static messages stored in an array so you’d need some other hardware to push your own characters through via the chip’s UART or otherwise. The AVR sends messages by converting the data into audio using PWM. That signal is fed into the crystal oscillator, which produces an amplitude modulated signal (AM) that can then be transmitted.

Check out his video after the break for a demonstration. He’s decoding the transmitted data using a free program called Ham Radio Deluxe.

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AM Singer: A Tiny AM Transmitter


[Simon Orr] wrote in to tell us about his AM transmitter prototype that he plans to put into production in a few months. The build is based on an “Easy AM Transmitter” featured in this Instructables article.

Interestingly enough, this device is capable of transmitting in the 100KHz to 480KHz frequencies. The AM band goes from 520 KHz to 1610KHz, so in order to hear this signal, one must actually tune the radio to twice the emitted frequency. This allows one to tune into the harmonic frequency and receive a signal in this range.

Using the harmonic frequency to transmit is an interesting concept by itself. Additionally, the idea that one could build this device with or without the kit in the future should appeal to experienced hackers and those just starting out alike. Check out the “AM Singer” prototype video after the break. Continue reading “AM Singer: A Tiny AM Transmitter”

Arduino Powered 2.4 GHz Spectrum Analyzer

[Fred] dropped a note in our tip line to let us know about arduino forum user [bilbo]’s latest project: A 3-in-one spectrum analyzer, oscilloscope, volt-meter combo. The build consists of an Arduino, radio board and Nokia 5110 LCD breakout board.  The (thin) video after the jump shows the rig in action. Though soldered to a full sized perf-board we can see later, smaller, battery powered versions prove useful in rooting out wayward bluetooth signals, or just finding that lost microwave oven. Although [bilbo] uses the same radio board as similar builds  his creation boasts several different display modes, as well as doubling as a volt meter and miniature-oscilloscope. There is no shortage of previous spectrum analyzer builds, but this one is the first one we have seen running on an Arduino.

Thanks for the tip [Fred]! If you feel like wedging some frequency scanning capabilities into your next project don’t forget to check out [bilbo]’s forum posts for source code!

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