ATmega1284 As An 8-voice 32 KHz Synthesizer

November 2, 2012 by Mike Szczys 10 Comments

A couple of things strike us about this 8-voice 32 kHz synthesizer. First is the cleanliness of the prototype. As you can see, each part has plenty of room on its own board and all are interconnected by 10-pin IDC ribbon connectors. But you’ll have to see the video after the break to enjoy the impressive sound that this puts out. You’ll hear it play the Super Mario Bros. theme; it does it with passion!

To get audio from the digital microcontroller [Mike] built his own R2R digital to analog converter. The resistor ladder is built from sixteen resistors, which feed a rail-to-rail amplifier. The sound is mono but the playback is polyphonic thanks to the work done by the ATmega1284. It is reading MIDI commands coming in from an external controller (we assume it’s the computer on which the hardware is sitting). The chip’s 128 KB of Flash memory leave plenty of room to store samples, which are selected from a lookup table based on the MIDI data. If more than one sample is to be played the chip averages the data and sets the 8-bit output port accordingly.

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Building A 100 MHz Frequency Counter

November 2, 2012 by Mike Szczys 5 Comments

The great thing about building with gates is the crazy speeds you can achieve by using hardware directly (as opposed to working with simple microcontrollers). This 100 MHz frequency counter is a great example. [Michael] just finished building it using a Papilio board.

Of course we’re not talking about discreet chips here. The Papilio is an FPGA development board which means he is building with hardware gates, but that is still done by writing code. Above, the rig is measuring a 25 MHz being generated by a second FPGA board. Using the Papilio’s on board 32 MHz clock the device is capable of counting a frequency up to 100 MHz. You can see it measuring a 96.875 MHz signal in the video after the break. One interesting thing about that clip is that near the end he touches the crystal’s case with his finger and the Hertz really jump for a moment.

If the 8-digit display looks familiar that’s because [Michael] recently published a library to use it with an FPGA.

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Laptop Motherboard Reborn As A Low-wattage Server

November 2, 2012 by Mike Szczys 52 Comments

[Darknezz] sent us a set of photos and some details about his damaged laptop motherboard turned into a server. A client brought him a Dell 1525 on which nothing was showing up on the LCD screen. The HDMI and VGA still worked, and he traced the problem to no signal coming out of the motherboard. He swapped the board out to get the laptop working again, but he client said he could keep the damaged one.

It has a dual-core CPU which meets his needs and since it’s meant to run off of a battery it’s as energy-efficient as possible. [Darknezz] dug through his parts bin and found a PSU that could supply the needed 19.5V at 3.5A. The connector didn’t match but it didn’t take him too long to patch into it using a spare Molex connector. He also needed a power button and ended up soldering a momentary push switch to a couple of pads which he traced out form the original connector. The only thing he actually ended up purchasing were the memory modules. Check out the photos he took of the alterations in the gallery after the break.

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Turning A 600 Mil Chip To 300 Mil

November 2, 2012 by Brian Benchoff 75 Comments

We’ve seen a few builds featuring NXP’s LPC1114 microcontroller before. This chip – the only breadboard friendly ARM microcontroller available – comes in a ‘still a little too large for prototyping’ 600 mil, 28 pin package. We won’t hazard a guess why NXP chose this rather large package, but the good news is it’s possible to shave this chip down to the more common 300 mil, 28-pin package used by AVRs and PICs.

In the video tutorial of this procedure, the chip is first taped down to a desktop CNC mill. 150 mil on each side of the die are removed, exposing the very cool-looking pattern of leads coming out of the chip. This isn’t enough area to solder, so the chip had to be further milled to expose some of the internal wiring.

After soldering everything to a set of pins, the new 300 mil package is covered in epoxy putty, milled down again into a nice cube shape and painted. Yes, the modified chip does work, and no, we can’t figure out why NXP chose a 600 mil package for this microcontroller over the far more common 300 mil chip.

Video after the break. Tip ‘o the hat to [Ian] for sending this one in.

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How Computers Work, Starting With Transistor Gates

November 1, 2012 by Mike Szczys 11 Comments

[Andrew Gibiansky] has just started a tutorial series called Computing with Transistors. It’s purpose is to pull back the many veiled layers between high level languages and the controlling of electrons. And fittingly this first post starts off by explaining voltage source, load, and current. Don’t be thrown by its simplicity though. [Andrew] quickly moves on to talk about switching transistors and how they are used to build gates like the OR NOR gate seen above.

If this is the least bit interesting you should also look back at the post about Nand 2 Tetris. It’s an online course that works its way through The Elements of Computing Systems text book. We’ve been following that journey ourselves, having made it through the hardware build in about a week. The assembler took about the same amount of time, and right now we’re in debugging hell trying to get the last function call and return parts of the VM translator to work right. We’ve used most of the skills needed in this journey before, but never all in one project. It really has shed a lot of light on the gaps in our knowledge, and we’re having a lot of fun at the same time!

[via Reddit]

BeagleBone Powers This Networked LED Marquee

November 1, 2012 by Mike Szczys 4 Comments

[Mahmut] calls this project SmartBox. It’s a BeagleBone controlled LED marquee which can pull down information off of the Internet.

The project started with the display itself. [Mahmut] used six 5×7 LED modules to populate a circuit board he produced himself. The low side of the modules is controlled by some MBI5026 constant current drivers, with PNP transistors on the high side. The display connects to the BeagleBone ARM board using a couple of IDC ribbon cable connectors. With that up and running he started working on the enclosure. The display board was modeled in Google SketchUp to ensure that the case design would fit it properly. The laser cut acrylic case is in two parts, the base holds the driver electronics, with a hinged section for adjusting the angle of the marquee.

So far there are a few different connectivity features which are shown off in the clip after the break. The BeagleBone has the ability to pull down Twitter feeds, notify about incoming email, and scroll messages.

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Controlling Google TV From A Raspberry Pi (or Other Networked Devices)

November 1, 2012 by Mike Szczys 9 Comments

Google TV is a network connected television. It does what you would think: plays television programs, streams media from the internet, and allows you to open URLs on your TV. But one nice feature is that it can also be controlled over the network rather than just via an IR remote. Google publishes apps which make this simple with a smartphone. But the communications protocols are open source, so [Leon Nicholls] wrote a Google TV remote control library in Java.

The video after the break shows him pairing a Raspberry Pi with his television. The image above is the pairing verification code you must enter on the remote hardware before control is authorized. Apparently this is a step that needs to happen every time if using Google’s Anymote library. [Leon] improved that, by saving the pairing data so that the first authorization is all that it takes.

He figures this could be used for home automation. We’re not sure what we’d use it for but we’d love to hear your ideas in the comments.