SVGA Monitor Identification Bits`

Nov 17, 2007 1 Replies
W

I give up: How does a Sony (FX-140) notebook recognize the presence of an external (VGA/SVGA) monitor? Many Google hits on the topic provide monitor ID bit identifications...and variations thereon. But NONE of them seem to work. That is: Grounding the indicated pins, in all possible combinations, does not cue the computer that a monitor is connected. It cannot be that the FX-140 requires active communication with a monitor, because the computer recognizes ANY connected monitor (have tried 5) whether they are powered or not.



Any hints? Diodes between pins...resistors...holy water?


Vote
Twitter Facebook LinkedIn
B

Monitor ID pins haven't been used for a LONG time. The ID solution used today is a VESA standard called the Display Data Channel (DDC), which is based on the I2C electrical interface. There are two pins on the VGA connector which support the DDC, one clock and one serial data, and the PC reads a 128-byte file called the EDID (Extended Display Identification Data) over this connection. You can no doubt get more information on this system by Googling for "DDC" and "EDID".

The simple presence of the monitor is also sometimes sensed by noting whether or not there is a load on any of several lines on the VGA output, including the RGB video pins (pins 1, 2, and 3) or the +5 VDC pin that is also provided under the DDC standard (pin 9).

Bob M.

Vote
Twitter Facebook LinkedIn

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required