Jinivus
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RPi Touchscreen - How to turn it off?

Thu Sep 10, 2015 12:49 pm

As subject says, looking for a method in raspbian to power off the display

I have tried:

Code: Select all

xset dpms force off
And it does "blank" the display but the "backlight" is still on. Is there any way to actually turn it off currently, without turning off the whole thing?

arista
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Re: RPi Touchscreen - How to turn it off?

Sat Sep 12, 2015 8:29 am

I'd like to know also how to power off the Official 7" Touch Display programmatically. If it is not possible, what kind of parts are needed?
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Aapo Rista

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jbeale
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Re: RPi Touchscreen - How to turn it off?

Sun Sep 13, 2015 7:19 pm

I would also like to know how to turn of the screen backlight.

By the way, I think the visual effect when you do 'sudo halt' is kind of interesting.

scotty101
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Re: RPi Touchscreen - How to turn it off?

Sun Sep 13, 2015 9:33 pm

jbeale wrote: By the way, I think the visual effect when you do 'sudo halt' is kind of interesting.
It is pretty amazing. I get two clusters of dots that look like the six side of a dice.
Electronic and Computer Engineer
Pi Interests: Home Automation, IOT, Python and Tkinter

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jbeale
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Re: RPi Touchscreen - How to turn it off?

Tue Sep 15, 2015 1:56 pm

Should I consider that the lack of any answer here, means that the backlight cannot be turned off? If I make an external circuit to cut the USB input power while it is still connected to a running Pi, will that hurt anything? What would I need to do to reinitialize after powering it back up?

dom
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Re: RPi Touchscreen - How to turn it off?

Tue Sep 15, 2015 2:25 pm

jbeale wrote:Should I consider that the lack of any answer here, means that the backlight cannot be turned off? If I make an external circuit to cut the USB input power while it is still connected to a running Pi, will that hurt anything? What would I need to do to reinitialize after powering it back up?
I believe the backlight can be controlled from software, but needs some plumbing to make it work (i.e. a backlight driver on firmware side and a vcgencmd to control it).

I suspect cutting power to display and then reapplying it won't work (there are I2C registers that need to be set up).

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jbeale
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Re: RPi Touchscreen - How to turn it off?

Tue Sep 15, 2015 4:35 pm

Thanks Dom, that's some useful info... so I gather the I2C register setup for the LCD display is inside some function that is not in any way accessible from userspace (apart from doing a reboot)?

gsh
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Re: RPi Touchscreen - How to turn it off?

Tue Sep 15, 2015 5:08 pm

Yeah, Dom's right,

The code to initialise the display is not hot pluggable, so you can't just pull the power from the display it just won't come back!

The PWM controls and the power on/off controls are hidden away in a little Atmel which has to be controlled from the GPU side (it has to be this way because we share that I2C bus with the camera). Currently there is an 'in-memory' communication scheme between the GPU and the ARM for the touchscreen but I've not yet implemented the controls for the PWM and power

I've just spent a couple of days fixing/working around a bug in the I2C drivers on the GPU so this should be next on my list. Although I'm not sure what the right solution is for the software interface for these (I'm assuming just implementing the pwm driver is enough)

Gordon
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jbeale
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Re: RPi Touchscreen - How to turn it off?

Tue Sep 15, 2015 5:43 pm

My interest is in minimizing power draw when the display is not in active use. So if I can turn the backlight PWM down to 0 and then the current draw for everything else is relatively small compared with the Pi itself, that's fine. If I need to save more power than that, I'd have to shutdown the Pi anyway and do a normal reboot to get it working again.

babelmonk
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Re: RPi Touchscreen - How to turn it off?

Wed Sep 16, 2015 6:25 am

+1, I'd really like to be able to control the PWM / turn the backlight off completely if possible.

I want to use the device as a home automation controller, and having it on all of the time takes too much power and will shorten the life of the display.

arista
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Re: RPi Touchscreen - How to turn it off?

Fri Sep 18, 2015 9:02 am

This page says turn off+on and brightness control is coming!
http://forums.pimoroni.com/t/official-7 ... en-faq/959
Can I turn it off/on from Raspbian?
No, not yet! But soon.

Can I control the backlight brightness?
No, not yet! But soon.
Edit: sorry, I was so excited that I didn't read Gordons post before posting this. :)
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morphious6
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Re: RPi Touchscreen - How to turn it off?

Fri Sep 18, 2015 12:44 pm

I too am looking for the same functionality. I would like to turn on the display with a PIR motion sensor and then have it time out after a certain amount of time with no activity. ( home automation system as well ) ...

lichtteil
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Re: RPi Touchscreen - How to turn it off?

Tue Oct 06, 2015 12:11 pm

I'm also planning to use a sensor to switch on the display, just like morphious6. I would appreciate a lot to have a command for switching on/off :)

pumpkinpi
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Re: RPi Touchscreen - How to turn it off?

Tue Oct 06, 2015 4:44 pm

I am in the same boat here. Would like to turn the backlight and display on based on a motion sensor.

PPi.

brx
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Re: RPi Touchscreen - How to turn it off?

Mon Nov 02, 2015 7:16 pm

Same situation here. This is such an obvious use case. Any progress on the backlight control yet?

jdb
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Re: RPi Touchscreen - How to turn it off?

Tue Nov 03, 2015 6:35 am

Backlight control is implemented in latest rpi-update firmware.
Rockets are loud.
https://astro-pi.org

pumpkinpi
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Re: RPi Touchscreen - How to turn it off?

Tue Nov 03, 2015 12:00 pm

Where do we find out how to implement it or control it?

PPi

cpfeil
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Re: RPi Touchscreen - How to turn it off?

Tue Nov 03, 2015 1:08 pm

Hi,

everything is written / discussed in this topic viewtopic.php?f=108.

That's how you control it:
echo 0 > /sys/class/backlight/rpi_backlight/bl_power
echo 1 > /sys/class/backlight/rpi_backlight/bl_power
Works fine for me!

best regards,
Christian

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RaTTuS
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Re: RPi Touchscreen - How to turn it off?

Tue Nov 03, 2015 1:46 pm

cpfeil wrote:Hi,

everything is written / discussed in this topic viewtopic.php?f=108.

That's how you control it:
echo 0 > /sys/class/backlight/rpi_backlight/bl_power
echo 1 > /sys/class/backlight/rpi_backlight/bl_power
Works fine for me!

best regards,
Christian
viewtopic.php?f=108&t=120968&start=25#p834085 <- working link
How To ask Questions :- http://www.catb.org/esr/faqs/smart-questions.html
WARNING - some parts of this post may be erroneous YMMV

1QC43qbL5FySu2Pi51vGqKqxy3UiJgukSX
Covfefe

pumpkinpi
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Re: RPi Touchscreen - How to turn it off?

Mon Nov 16, 2015 2:03 am

I must be missing something really obvious. Is there not a way to automatically disable the backlight after a fixed period of time. The screen turns black after a certain period. I would like the backlight to turn off too.

I have updated and upgraded my OS.

Also, I try this:

Code: Select all

echo 1 > /sys/class/backlight/rpi_backlight/bl_power
-bash: /sys/class/backlight/rpi_backlight/bl_power: No such file or directory
The "backlight" folder exists, but it is empty. No files or folders there. I thought I need to write a file there called bl_power and put a 0 or a 1 in it, but the OS is not letting me do anything in that folder even with sudo.

Can anybody help?

PPi

Dataworm
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Re: RPi Touchscreen - How to turn it off?

Mon Nov 16, 2015 8:55 am

I'm not quite sure whether apt-get dist-upgrade is enough. I guess you also have to do rpi-update, did you do so?!

pumpkinpi
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Re: RPi Touchscreen - How to turn it off?

Mon Nov 16, 2015 2:07 pm

I did:

Code: Select all

sudo apt-get update
sudo apt-get upgrade
sudo apt-get update
PPi

Dataworm
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Re: RPi Touchscreen - How to turn it off?

Mon Nov 16, 2015 2:12 pm

So you could execute rpi-update and see if that solves your problem! ;-)

JimmyN
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Re: RPi Touchscreen - How to turn it off?

Mon Nov 16, 2015 3:15 pm

As @dataworm suggested use "sudo rpi-update" to update the firmware. Normally you avoid that command, since it could cause problems, but you'll need to do it for the display backlight function. After running "rpi-update" you will see all the backlight folders have been added and you can then change the value in "bl_power".

pumpkinpi
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Re: RPi Touchscreen - How to turn it off?

Mon Nov 16, 2015 3:29 pm

Will do. Thanks folks!

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