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 Xbox 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 is actually a PC. The major differ- ence between the Xbox and a normal PC is that the operating system is stored entirely in Flash memory and users can- not add any functionality to the system. There is also a protection system that pre- vents any software from being accepted if it does not have a digital 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 o PC to run Linux. 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 1 (red) : +5 V that there is no keyboard for the Xbox. That's what we wont to remedy here. +SV red Pin 2 (white) : D— As usual with game computers, the Xbox 2. D- white has connectors for controllers (enhanced , D. green Pin 3 (green) : 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 a form that is totally new to us. After a bit of detective The other wires are used for the actual Four terminals of the USB connector, as work, it turns 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 o good 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. If you fit a stan- easier to recognise. between the lines. As a second test, we dard USB connector somewhere on the For the installation, you will some wire recommend checking whether a voltage enclosure and wire it to the signal lines and a USB connector (Type A). That's the can be measured between pin 1 of the for one of the connectors, you can then some type of connector as the USB con- USB connector (+3.6 to 5 V) and pin 4 connect a USB 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 a connector, along with switched on. If the test results are all OK, sticks can be used by the Xbox as Xbox the proper pin numbers. the USB connector is ready for use. memory cards. USB memory sticks are a Find a place 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 a small hand-held games also use a USB keyboard to make The wires to the connector at the front can router or a drill 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 7-8/2005 - delctor electronics 67 .