Print

[St0mPeR]

QUOTE

Using the Xbox's internal sync signals
This method will deliver the best sync signals but is also the most difficult to build. You should have several years of soldering experience with SMD devices before trying this method.

The digital interface between the NVidia GPU and the Conexant chip uses a HSYNC and VSYNC signal. Unfortunately these signals are only used internally, they are not available on the AVIP.

It's not advisable to use the HSYNC and VSYNC signals directly, since the sync lines of a monitor are usually terminated with a 75 Ohm load. Instead you have to use a buffer to drive the signals. To make matters worse, the interface between the Conexant chip and the GPU uses only 1.5 signal voltage. However, some monitors are able to cope with this.

HSYNC is available at pin 35 of the CX25871, VSYNC at pin 36. I recommend to use two Schmitt-Triggers of a 74HC14 as buffers. The supply voltage of the 74HC14 has to be 1.5 Volt (available from pin 40 of the CX25871), otherwise the input threshold of the Schmitt-Trigger is too high.

I strongly advise not to solder wires directly onto the CX25871, since you're likely to shorten two or more pins. The sync signals are also available from two small soldering pads close to the upper edge of the GPU. Use a multimeter to find them. (Points on top of motherboard) (http://members.cox.n...n1687/con3e.JPG) (Points underneath motherboard) (http://members.cox.n...687/conunde.JPG)

Connect the ouput of the buffer driven by pin 35 of the Conexant to pin 13 of the VGA connector. Connect output of the buffer driven by pin 36 of the Conexant to pin 14 of the VGA connector.

Since this method doesn't depend on sync pulses embedded in the green signal it doesn't suffer from the colour problems described above.

I want to do this, but the problem i'm having is how dose this 74HC14 chip get wired up? I have 2 of thes chips i just need help running xbox through it and into VGA plug.