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Guitar Hero jams go wireless

Posted: 14 Feb 2008 ?? ?Print Version ?Bookmark and Share

Keywords:Guitar Hero teardown? Les Paul guitar? PCB? passive components? RF signal?

Activision's Guitar Hero series has been big. Really big. Reports peg total sales of the Guitar Hero lineup at about $1 billion as of the start of 2008.

The game's premise is pretty simple: Players must use five buttons on the fret board, combined with a strum bar and whammy bar, to follow along with game music as closely as possible to maximize their score. They can garner bonus points in the Star Power mode, which requires the guitar neck to be held vertically.

Much as musicians often go wireless to allow for freedom onstage, the Xbox 360 Guitar Hero III Les Paul wireless controller, manufactured by RedOctane, lets players do spinning jumps off the couch. The $99 RedOctane/Activision package purchased for this teardown includes both the game and a single wireless controller styled after Gibson's popular Les Paul guitar.

The controller neck can be unplugged to make for more-compact carrying. Because the fret control buttons must pass through to the internal electronics, there is a small patch of PCB at the end of the neck that mates to a pogo-pin connector block in the controller body, letting the carbon-tipped elastomer fret key buttons and associated circuit board contacts in the neck link up with the core controller electronics.

'Air guitar'
Opening up the guitar body, one finds what is largely empty space. There's an "air guitar" joke there, but the point is that the electronics are kept simple to meet the target price at a profit.

Outside of the most complex assembly, four separate circuit boardsall made of inexpensive phenolic material, like that of the neck fret board contact assemblysupport passive components for interface and control. One circuit board holds the switches activated by the motion of the strum bar. Another supports flash-plated contacts for the Back and Start buttons. The third holds an RJ-11 telephone jack connector and Connect button, and the fourth provides a jack for what appears to be an optional headset connector. Instructions make only passing reference to the RJ-11 and eight-pin jacks as points of "future expansion," but PCB markings and shielded cable all indicate a microphone will enter the picture. The eight-pin port is indeed identical to that used for headset expansion in a standard Xbox 360 game pad controller. The telephone-style jack is rumored to support foot pedals, but the manufacturer has yet to disclose optional plug-ins.

Guitar Hero

The number of counterfeit devices coming in over the past few years could indicate an alarming trend.
(Click to view teardown.)

For the primary active electronics, a more-stable surface-mount platform of glass-epoxy circuit board is used, with chips on the topside and additional control contacts on the bottom. The four-layer board supports both controller and radio functions along with the antenna.

The lower right corner of the board supports a planar inverted-F antenna (PIFA) for communication back to the 360 console. The top of the F is grounded; the middle bar provides the feed/pick point for the RF signal. Designed for 2.4GHz operation, the PIFA is a great example of the black art of antenna design. Rather than shunt the signal, the ground pointin combination with the antenna geometriesgives the "backbone" of the F the highest emitter/receiver gain possible.

Proprietary design
Chips for the controller are few and, with one exception, all of a proprietary-to-Microsoft nature. National Semiconductor is the big winner here, with design wins for both the mixed-signal MCU (SC14470C) and the RF radio transceiver (LMX4270C). The controller must indeed support some level of analog peripherals, since the GH3 controller whammy bar is tied to a potentiometer, which must be digitized and monitored to affect game control. The headset jack wires directly to the SC14470C.

A memory chip of unknown origin supplies embedded code. The die of this little eight-pin part is, on the surface, unremarkable. As it turns out, though, the top chip layer provides a protective shield to discourage tampering, code extraction and other reverse-engineering feats. Once perturbed at the surface, the device detects the intrusion and essentially erases itself. Such anti-hacking measures speak to Microsoft's careful control of the Xbox 360's wireless-link technology.

The main addition to the core proprietary Xbox wireless components relates to the Star Power bonus-point mode. Since the guitar must be played with the neck in a vertical position for the bonus mode, orientation sensing is a factor. This need is fulfilled by a Freescale MMA7360L three-axis accelerometer.

RedOctane and Activision have made a similar GH3 wireless guitar available for the Sony Playstation 3.

- David Carey
President, Portelligent




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