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ab1jx
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Location: Heath, MA USA
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Re: Official Touchscreen Display Questions

Tue Feb 20, 2018 4:09 am

JamesPi123 wrote:
Thu Apr 13, 2017 8:43 pm
billintad wrote:I think you are supposed to use "Recommended peripherals", but a forum dedicated to "screens" might be a good idea as there have been many threads about that topic.

The desktop display (startx) does go blank after a period of no input . It is immediately refreshed by just touching the screen. I suppose there must be a parameter somewhere that controls the length of time spent waiting for input. I haven't looked.

I have not experienced screen blanking when the command line is being used, but I don't use the command line for any length of time. I will just leave it running for a while and see what happens.
It's designed to stop screen burn-in, although it dosen't really happen anymore.
For blanking try this at a command line:

Code: Select all

setterm --blank 0
It's at a lower level than X so it affects both. See the setterm man page. I used to spend hours getting just the right setup on xscreensaver but no matter how much I messed around in X the screen would shut off after 10 minutes. It comes from the kernel.

edit: well, neither xterm or rxvt supports blanking is the message I get, I thought it would apply to the whole screen. This is related to "cat /sys/module/kernel/parameters/consoleblank" which by default seems to be 600 (10 minutes). Good discussion of it at https://superuser.com/questions/152347/ ... g-behavior There's also a VESA powerdown interval, I'm not sure when that comes into play.

Oh, I just ordered one of the official LED displays after thinking about it for a year or so. I want to build a little tablet with some 18650 lithium cells powering it and an LM2596 switching regulator. I came to this FAQ because there's precious little info about the backlight, it's not mentioned in the PDF from Newark at all. I gather there is one but somebody wanted to know how you turn it off and got no answer. I'd like to know can I break out the lead to it and put a dimmer on it?

Oh, and LCDs aren't totally immune to screen burn. I used one once that had to be driven by AC. It would work on DC but after a while it turned black. The polarity had to be carefully reversed 50% of the time so you had to use an inverter. I know I've seen LCD TVs with screen burn from having something fixed on the screen for a long time, like a kiosk where they're on for years..

hwdornbush
Posts: 21
Joined: Fri Jan 20, 2017 7:08 pm

Re: STICKY: Official Touchscreen Display FAQ

Wed Aug 07, 2019 11:37 pm

How do I switch from HMDI to the touchscreen display? I have an image of Raspbian that works with an HDMI monitor and I want to use it with the touchscreen display. If I plug the SD card with the image into an RPi 3B which has a touchscreen display attached to it, I see a slight gray screen on the touchscreen display but that is all. If I plug an HDMI monitor into the RPi and then reboot, the desktop appears on the HDMI monitor. The touch of the touchscreen is still active as I can touch the screen and drag the mouse pointer around and click on an input box, but I cannot see the desktop on the touchscreen display. Raspbian appears to remember what monitor it was first used with and wants to continue to use that monitor. So how do I get Raspbian to switch from using the HDMI monitor to the touchscreen monitor?

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