monitor power off. how does the pc signal the monitor to turn off?

Comments

• P!-Ro Posts: 1,189

  2010-05-30 02:45 edited 2010-05-30 02:45

  Doesn't it turn off when the graphics card stops? Perhaps you could detect it by monitoring the signal activity on the pins.
  
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• mctrivia Posts: 3,772

  2010-05-30 02:47 edited 2010-05-30 02:47

  it must be differen't. if you pull the cable out it says lost signal. when windows says to shut off it just goes black and starts blinking the power led.
  
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• P!-Ro Posts: 1,189

  2010-05-30 03:00 edited 2010-05-30 03:00

  I remember reading somewhere (popsci maybe?) that if you tie certain pins and add some sort of resistance you could trick a laptop into thinking there's a second monitor. So, perhaps--assuming I'm right about the pins--if it's connected correctly then when the signal stops it will go into low power mode.
  
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• mctrivia Posts: 3,772

  2010-05-30 03:09 edited 2010-05-30 03:09

  with VGA cables pins 11,12,15 are used to identify the monitor type. i beleive older monitors used resistors for id but newer ones use i2C over pins 12 & 15.
  
  dvi does not have id pins like vga has. it does however have 2 i2c pins so that probably took the place of the 3 id pins on vga. I do see that pin 16 is for hot plug detection so it may be as simple as detecting if data is being transmitted or not and the monitor uses pin 16 to tell the difference between unpluged and turn off.
  
  my logic analyser is way to slow to scope DVI signals
  
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• Chris Savage Parallax Engineering Posts: 14,406

  2010-05-30 03:18 edited 2010-05-30 03:18

  Actually it varies with the monitor but pi'd is actually right for the most part. Lack of video sync usually puts the monitor into standby mode. The problem is that some monitors can tell when they're disconnected from a PC by floating pins and they go into a demo mode. On a DOS PC you can simulate putting the monitor into low-power mode (the ones that detect sync) by clearing the video refresh register and calling the correct INT (can be done in DEBUG).
  
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• mctrivia Posts: 3,772

  2010-05-30 03:22 edited 2010-05-30 03:22

  so is that what windows does? just stop sending data?
  
  I am not trying to shut down the monitor. i am trying to detect when windows has shut down the monitor. I want to shut down my stereo when the monitor gets shut down.
  
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• mctrivia Posts: 3,772

  2010-05-30 03:23 edited 2010-05-30 03:23

  I just realized I am using my computer monitor as a digital picture frame. it never gets turned off except when i hit the switch. guess i need to just use a power bar so the monitor and stereo have 1 switch to turn off.
  
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• BradC Posts: 2,601

  2010-05-30 04:12 edited 2010-05-30 04:12

  search for DPMS & DMPM. Not a lot of info on DMPM unfortunately.
  
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• Chris Savage Parallax Engineering Posts: 14,406

  2010-05-30 06:25 edited 2010-05-30 06:25

  @BradC - Yeah, there's the protocols for communication. I was trying to take the easy road. [noparse];)[/noparse]
  
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  Parallax Engineering
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