tered with two electrolytic capacitors of other uses. You can, for example, make Keep in mind the safety requirements 220 uF each. a thermostat for heating by swopping the when building and mounting the circuit. The design can also be used for countless inputs of the opamp.

USB for the

Paul Goossens

The Xbox is the well-known Microsoft game computer. The fact that the Xbox is based on PC technology should hardly be surprising, since Microsoft specialises in this computer architecture. It's also not especially remarkable that if you open up an Xbox, you'll find several well-known ICs from the PC world. In fact, the Xbox actuallyis PC.a The major differ- ence between the Xbox and normala PC is that the is stored entirely in Flash memory and users can- not add any functionality to the system. There alsois protectiona system that pre- vents any software from being accepted if it does not have digitala signature from Microsoft. At least, that was the intention. Naturally, there ore people who have cracked the

Xbox protection system and use the Xbox USB Type A as PCo to run . We plan to publish Table 1. more information about this in Elektor Electronics in the near future. The biggest USB connections problem with running Linux on an Xbox is Pin (red)1 +5: V that there is no keyboard for the Xbox.

That's what we wont to remedy here. +SV red Pin (white)2 D: — As usual with game computers, the Xbox 2. D- white has connectors for controllers (enhanced , D. green Pin (green)3 D+ : Gt4D black joysticks) for playing the games. The Xbox Pin 4 (black) : GND - has four such connecters on the front of the enclosure. They have forma that is totally new to us. After bita of detective The other wires are used for the actual Four terminals of the USB connector, as work, turnsit out that the signals on these USB signals. A nice detail is that shown in Table 1. connectors ore actually quite familiar: Microsoft uses exactly the some colours It's goodo ideo to check the connections they're USB signals. for these wires os those specified in the before using the modified unit, in order to Once you know that, it's easy to connect USB standard, which makes them much ensure that there aren't any shorts a keyboard to the Xbox. youIf fit a stan- easier to recognise. between the lines. As seconda test, we dard USB connector somewhere on the For the installation, you will some wire recommend checking whether voltagea enclosure and wire toit the signal lines and USBa connector (Type A). That's the can be measured between pin of1 the for one of the connectors, you can then some type of connector as the USB con- USB connector (+3.6 to V)5 and pin 4 connect USBa keyboard. Another benefit nectors in a PC. Figure 2 shows an (ground) after the Xbox power has been of this is that most types of USB memory example of such connector,a along with switched on. theIf test results are all OK, sticks can be used by the Xbox as Xbox the proper pin numbers. the USB connector readyis for use. memory cards. USB memory sticks are a Find placea on the Xbox where the con• USB keyboards (and USB mice) are sup- lot less expensive thon 'genuine' Xbox nectar can be fitted. It's easy to make a ported by Xbox Linux, and some Xbox memory cards. hole in the case with smalla hand-held games also use USBa keyboard to make The wires to the connector at the front can router or drilla and a small file. Next, it easier to control the game and/or chat be clearly seen in Figure 1. The yellow make connections between the four wires with other players. wire is not important for our purposes. leading to the Xbox connector and the

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