2

I have seen many small displays that work with the Pi, however I am wondering if any of them can be turned completely on/off via the Pi. If so, what should I look for? many are GPIO based (especially the smaller ones or touch-sensitive ones), so CEC code support isn't quite enough.

The application I want to use this for is a "weather display" that shows the weather forecast, but only during certain hours (not during the night - it needs to be completely dark then).

  • 2
    You can switch any electrical equipment on and off by using a gpio to operate a switch. If you could home in on a preferred display it may be easier to offer a practical solution. – joan Nov 17 '14 at 21:55
  • @joan - I am still looking for a display, thus the question - but it would be somewhat of a PITA to use a GPIO switch to control a device that plugs into the GPIO already, and if it uses the 3v from the GPIO to power itself directly... also not all electronics like their power being yanked and may create spikes/etc. that could be bad for the pi (as in cause crashes/reboots), especially if they share a common power source. – user2813274 Nov 17 '14 at 22:05
  • I can tell you how to switch a 64*32 pixel OLED display to dark. Is that any good for your weather application? – joan Nov 17 '14 at 22:27
  • @joan I think I need more resolution than that..something like 320x240 at a minimum - lets say displays similar to these: HDMI, USB, GPIO without the pi being off – user2813274 Nov 17 '14 at 22:32
  • 1
    That's why you need to home in on a preferred display. Some people don't like offering answers to broad questions only to be told the answer doesn't meet some undeclared requirement. – joan Nov 17 '14 at 22:38
2

I use a small screen with a composite connection that goes black when I turn of the signal (tvservice -o). This screen usually sells as car reverse monitor.

  • Does it also automatically turn on when a signal is received? – user2813274 Nov 18 '14 at 17:55
  • Yes, of course. The trick is, though, that you have to switch the bit depth for a screen refresh. I use this line in a script to turn it back on: ` tvservice -c "NTSC 4:3" && fbset -depth 8 && fbset -xres 654 -yres 431 -depth 16 && xrefresh -d :0`. – PiEnthusiast Nov 18 '14 at 20:17
2

There is an HDMI based protocol called CEC via which some TVs/monitors can be turned off. This requires some software, e.g., libcec, which is in raspbian.

I haven't tried it, but the client (cec-client) is in the cec-utils package, which presumably pulls in the libcec package too.

If you search around you will find various pi/linux related information about this, e.g.:

Turning a device off seems to be one of the more obscure commands. If that's what you want and you have not bought anything yet, check around first and you should be able to get something that works. Presuming you have a few HDMI displays already, you're free to try it with those too.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.