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Learned something new: VGA cable pinouts can vary! (KVM & monitor standby)

By robo_dev ·
Think fast: How many different pinouts are used in VGA cables, which use the 15 pin cable?

Answer: Three

I got a KVM to share a keyboard/display/mouse with two PCs, plugged it in, and it worked OK.

BUT the monitor would not go to standby mode.

I had grabbed an old VGA cable from the cable-pile and plugged it in.

Everything worked fine, except standby mode. Monitor would go to 'signal lost' mode after twenty minutes, and never go into standby).

I was ready to return the (Belkin Flip) KVM to the store. After doing more research, I learnt that there are actually multiple VGA standards that use the same 15pin connector.

So I found the VGA cable that shipped with the display and DPMS (display power management signaling) works properly once again, with the KVM in place.

The issue is that some cables are missing pin-5 and pin-9, it's apparently pin-11 that's the sense pin. Further, pins 5 and 11 are sometimes tied to pin-10 on some other cables, which effectively grounds-out the DPMS.

As it turns out, plug-and-play uses the newer (VESA DDC2) VGA standard, so the wrong cable may also make plug-and-play not work as well.

"Classic" VGA:
1 Red (Analog)
2 Green (Analog)
3 Blue (Analog)
4 Reserved
5 Ground
6 Red Return
7 Green Return
8 Blue Retuen
9 No Connect
10 Ground
11 (ID0) GND (Color)
12 (ID1) NC (Color)
13 Horzontal Sync
14 Vertical Sync
15 No Connect

"VESA DDC2"
Pin 1 RED Red video
Pin 2 GREEN Green video
Pin 3 BLUE Blue video
Pin 4 N/C Not connected
Pin 5 GND Ground (HSync)
Pin 6 RED_RTN Red return
Pin 7 GREEN_RTN Green return
Pin 8 BLUE_RTN Blue return
Pin 9 +5 V +5 V DC
Pin 10 GND Ground (VSync, DDC)
Pin 11 N/C Not connected
Pin 12 SDA I?C data
Pin 13 HSync Horizontal sync
Pin 14 VSync Vertical sync
Pin 15 SCL I?C clock

Ya learn something new everyday.....

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I'll be dipped.

by CharlieSpencer In reply to Learned something new: V ...

As you said, we learn something new every day.

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I was cursing Belkin and ready to return the KVM

by robo_dev In reply to I'll be dipped.

...and never thought is was the stupid cable.

Of course having to return something to Fry's means getting to go shop at Frys, which is never a bad thing.

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Help ! Monitor - Standby problem

by mbean In reply to Learned something new: V ...

Hello, I found your post very interesting since I am having the EXACT same problem- I have a media player connected via VGA cable, and only 5 pins are used the RGBHV - per your pin=out listed above this is pins 1,2,3,13,14

and then 2 conductors are tied to shield. If I wanted my monitor to go into standby - which pins would I need to connect? And would i need to connect ground to them - or +5 to get the standby function to work?

Thanks,

Mike

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