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Bat Country's "Thank You DJs" Special!

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Uploaded on Oct 29, 2011

Note: Because some people can't seem to offer constructive criticism, comments have now been disabled for this video. Cheers!

In a rather unorthodox turn, our lead engineer has been screwing around with amateur electrical engineering by figuring out how to read a DJ Hero turntable on a PC rather than doing what he's SUPPOSED to be doing and modding Minecraft.

We think it's okay, though. Who hasn't wanted a 55-inch Etch-A-Sketch with 10-inch Dials? That's right. EVIL SANTA. Don't be like Evil Santa, enjoy the giant Etch-A-Sketch.

Plus, if you watch, you might get a peek at our next Minecraft mod...

TECHNICAL JARGON AHEAD

The DJ Hero turntable module is a pretty smart little device. It's based on a Microchip PIC polling an optical encoder and three buttons. The optical encoder is mounted on the bottom of the free-spinning turntable and is triggered by a toothed rail running along the inner edge of the bottom plastic shell of the turntable module itself. It also takes input from a momentary switch which shorts an I/O pin to Ground if the turntable module is plugged in on the left-hand side of the center deck.

DJ Hero turntable modules communicate over I2C. The right-hand turntable will respond at address 0x0D, the left-hand turntable (by virtue of its depressed momentary switch) will respond at address 0x0E.

Write a single byte of 0x00 to the turntable module to reset the send buffer, then issue a request for 23 bytes. The purpose of the first 19 bytes is unknown, but byte 20 contains the turntable button state in the least significant three bits in the order G-R-B, byte 21 contains the turntable platter distance traveled since the last inquiry, and byte 22 contains the sign of the distance traveled (positive clockwise, negative anti-clockwise). Byte 23 is always zero.

Turntable modules have been found to respond to inquiries as frequently as every 2ms, allowing upwards of a 500Hz polling rate, which is more than often enough to ensure that a human-spun platter will never travel fast enough to cause sign wrap-around.

In our case, we're using a Teensy 2.0, which is an Atmel ATMega32U4, running the Arduino bootloader, on a small carrier PCB. with pin headers. Schematics are considered largely unnecessary insofar as the LEDs and micro-switches are wired up as one might expect based on the Teensy 2.0's "Blink" demo, and the turntables themselves can connect directly to the I2C bus without needing pull-up resistors.

Any questions specific to DJ Hero turntable PC interoperability can be directed to rholtz at batcountryentertainment.com.

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