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Changing Power Mode? #36

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Platypus2 opened this issue Oct 20, 2017 · 10 comments
Open

Changing Power Mode? #36

Platypus2 opened this issue Oct 20, 2017 · 10 comments

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@Platypus2
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Platypus2 commented Oct 20, 2017 •
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I recently started running ddcutil on a Pi to easily switch input modes on my Dell monitor. No problems so far.

I noticed with the ddcutil capabilities command that I also had:

Feature: D6 (Power mode)
Values:
01: DPM: On, DPMS: Off
04: DPM: Off, DPMS: Off
05: Write only value to turn off display

Is this safe to use? I did try it, turning off worked fine with 'ddcutil setvcp D6 x05'.

I set it back on, 'ddcutil setvcp D6 x01' (which is what it was when I hadn't touched it). That also worked, but I got this 'additional' response:

Setting value failed for feature d6. rc=DDCRC_RETRIES(-3015): maximum retries exceeded

Do you know why this might come up even though it worked fine? I would be happier knowing why it happened and whether it was safe to use frequently. Seems to happen constantly.

Should I get some logs to further find out why?
@Platypus2
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Platypus2 commented Oct 20, 2017 •
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I noticed if I set the monitor on when it is, the command does not return the same error. It only seems to happen when turning the monitor off -> on. On -> off or on - on is fine.

I ran

ddcutil setvcp D6 x01 --trace ddc

This is the output: https://pastebin.com/V2pTKQqk

Also:

ddcutil environment --verbose
https://pastebin.com/gWHeq8Q6

ddcutil interrogate
https://pastebin.com/k05QmNsu

Any idea what the Segmentation fault might be from? Anything else that might be useful?

@rockowitz
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rockowitz commented Oct 20, 2017 via email

@Platypus2
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Platypus2 commented Oct 20, 2017 •
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Thanks for the reply :)

First, a word of caution. Consider the output of capabilities to a
hint, not a guarantee. The capabilities string returned by the monitor
is often wrong - ddcutil does not rely on it. To see the full set of
values defined by the spec:

I probably should have waited for that word of caution, but it worked nonetheless.

ddcutil vcpinfo d6 --verbose

ddcutil vcpinfo d6 --verbose.txt

But note that a given monitor need not implement all possible values,
and for some VCP codes may implement values not defined in the spec. To
see what values the monitor actually supports, try setting the value
with setvcp and then check it with getvcp.

This is what I get after turning the monitor back on with setvcp. It is exactly the same as I got when I did getvcp before evening trying to set the power mode.

pi@raspberrypi:~ $ ddcutil getvcp D6
VCP code 0xd6 (Power mode ): DPM: On, DPMS: Off (sl=0x01)

Did you set it back on by physically turning the monitor on? Or were
you able to use the setvcp command to turn it on? I would be surprised
if that worked.

I was surprised as well to be honest - but yes it does work setting it back on after turning it off. I used x05 to turn off, and x01 turn back on. It works, aside from this 'error' of maximum retries exceeded, but the monitor does in fact turn back on.
It's not really 'turned off', its a dell monitor with a touch panel, so it has to be on to some degree to detect the touch. I can even switch input source with the monitor in this state - this is what I tried first before attempting the power mode (I switched the monitor off with touch and then sent the input source command and it was successfully changed with the monitor 'off').

Try issuing the setvcp command with the --verbose option. That will
give a detailed report of what is happening.

ddcutil setvcp D6 x01 --verbose.txt
ddcutil setvcp D6 x01 --trace ddc.txt

Does that help at all, seems it is failing when trying to verify that it worked? I guess that explains why the monitor turned on successfully but I still get this error as it just can't verify that it worked?

Please collect the output of command "ddcutil interrogate" in a file and
send it as an attachment. That should help me better understand your
environment.

ddcutil interrogate.txt

@rockowitz
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rockowitz commented Oct 21, 2017 via email

@Platypus2
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Platypus2 commented Oct 21, 2017 •
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Thank you for the help :)

Most interesting. Which model?

Little bit of background - I have two Dell U2715h. They both currently have 3 (out of 4) inputs plugged in and I find myself frequently having to switch between them throughout the day. I stumbled upon the Dell Display Manager and the ability to switch input sources via the command line with it, but quickly found it was windows only which eventually led me to ddcutil :).
My plan at the moment was to use a couple of Pis to change the input source, probably link them together via ethernet and control one via bluetooth and have that control the other via SSH. That way I can switch using my bluetooth keyboard (and a script). Something I thought of trying was to change the input source when the monitor was 'turned off'. To my surprised it worked so I figured there must be someway to turn the monitor off and on if the source switching worked - what would you expect to happen in this situation? I'd have figured something like a 'no display found' error?

What happens if you issue the command "ddcutil getvcp d6 --verbose" after a few seconds. Does getvcp work then?

Yes it does work without any error message - attached:
ddcutil getvcp D6 --verbose.txt

If it does, as a work around I'd suggest adding the "--noverify" option to the setvcp command.

I can confirm that using ddcutil setvcp D6 x01 --noverify works as expected without returning an error of maximum retries exceeded. While I'm more than happy to help - in the short term I presume I'm okay to use this considering it works and no errors are occuring?

Do you have valgrind installed? If so, running the command valgrind ddcutil interrogate --trace all

I just installed it, it seemed to get stuck, I waited for a few minutes but nothing else happen - don't think thats normal. It wouldn't even let me escape out of it. Nonetheless here is the output that I managed to get from it before it gets stuck:

valgrind ddcutil interrogate --trace all.txt

I ran the ddcutil interrogate --trace all as well just in case that provided any more information:

ddcutil interrogate --trace all.txt

I'd very much appreciate if you can do this, as I don't have a Pi here to test with.

No problem, I have a few Pis and img backups. If the monitor supports stuff like this (switching input sources without it being set to that source to begin with etc), I feel the Pis can be really useful for this sort of thing :D

@rockowitz
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rockowitz commented Oct 21, 2017 via email

@Platypus2
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Platypus2 commented Oct 21, 2017 •
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It's getting stuck during valgrind initialization.

Is that a valgrind installation problem then?

How are you building/installing ddcutil?

I built it from source following the documentation provided here:
http://www.ddcutil.com/building/

Installing the packages required before compiling on the pi itself. I also changed the config settings as detailed here:
http://www.ddcutil.com/raspberry/

Also, what values are returned by the following commands:

arch

armv7l

uname -m

armv7l

uname -p

unknown

uname -i

unknown

Let me know if you need anything else.

@Antoron
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Antoron commented Jun 18, 2018

I was very surprised, that 'ddcutil setvcp D6 x01' command worked for my Viewsonic vp2250wb when I switched it off with official 'd6 5'. It turned it on several timed and then stopped. Only physical button helped. When I changed OFF command to 'D6 x05' - ON became usable again! And vice versa. Display can be off for several hours and then be successfully turned on. Tried --verify, --maxtries, etc. looks like that only a change does the case. Not always. But it could be turned ONLY with 'ddcutil setvcp D6 x01' command!
Is it possible to understand a dependency here?

@rockowitz
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rockowitz commented Jun 20, 2018 via email

@tkna91
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tkna91 commented Feb 16, 2024

In my environment, it often failed when turning On/Off displays with the same model number but different serial numbers. I repeated the process until it succeeded and it generally worked.

# power off
for i in {1..99} ; do
    ddcutil --model="VY249" --sn="R2LMRS000394" setvcp d6 x05 && break
done
for i in {1..99} ; do
    ddcutil --model="VY249" --sn="R2LMRS005074" setvcp d6 x05 && break
done

# power on
for i in {1..99} ; do
    ddcutil --model="VY249" --sn="R2LMRS000394" setvcp d6 x01 && break
done
for i in {1..99} ; do
    ddcutil --model="VY249" --sn="R2LMRS005074" setvcp d6 x01 && break
done

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@Platypus2 @rockowitz @Antoron @tkna91