Doogals
Posts: 50
Joined: Sat Apr 02, 2016 8:55 pm

SOLVED!: HDMI Boot Sequence (10.1" LCD)

Fri Mar 30, 2018 3:57 pm

I have a Pi3 running LibreELEC connected to a 10.1" portable DVD player via HDMI, both are connected to the same 12V DC (in-car) power source.

The 10.1" DVD player only seems to recognize the HDMI signal if it's powered on before the Pi3 boots up, however both devices are always powered on at the same time in this setup.

Is the only way to resolve this issue powering on the screen before powering on the Pi3?

I have checked config.txt to make sure HDMI hotplug is enabled:

Code: Select all

# Force HDMI even if unplugged or powered off
# hdmi_force_hotplug=1 
Any other ideas?
Last edited by Doogals on Fri Mar 30, 2018 6:08 pm, edited 2 times in total.

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rpdom
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Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: HDMI Boot Sequence (10.1" LCD)

Fri Mar 30, 2018 4:24 pm

There is a way around this. You can make the Pi read the monitor configuration from a file instead of from the monitor itself. That way it will assume that particular monitor is connected and configure for it.

The steps are:

1. Turn on the monitor, then boot the Pi. You need to do this just once, to read the config from the monitor.

2. run sudo tvservice -d /boot/edid.dat This dumps the monitor config to a file which will be read at boot time.

3. Edit /boot/config.txt. Remove any "hdmi_" and other monitor related lines. Add the line edidfile=1 and you're done.

klricks
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Location: Grants Pass, OR, USA
Contact: Website

Re: HDMI Boot Sequence (10.1" LCD)

Fri Mar 30, 2018 5:08 pm

Doogals wrote:
Fri Mar 30, 2018 3:57 pm
I have a Pi3 running LibreELEC connected to a 10.1" portable DVD player via HDMI, both are connected to the same 12V DC (in-car) power source.

The 10.1" DVD player only seems to recognize the HDMI signal if it's powered on before the Pi3 boots up, however both devices are always powered on at the same time in this setup.

Is the only way to resolve this issue powering on the screen before powering on the Pi3?

I have checked config.txt to make sure HDMI hotplug is enabled:

Code: Select all

# Force HDMI even if unplugged or powered off
# hdmi_force_hotplug=1 
Any other ideas?
If the above is a Copy & Paste from your config.txt then hotplug is disabled. You have to remove the # to enable the command.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

Doogals
Posts: 50
Joined: Sat Apr 02, 2016 8:55 pm

Re: HDMI Boot Sequence (10.1" LCD)

Fri Mar 30, 2018 6:00 pm

klricks wrote: If the above is a Copy & Paste from your config.txt then hotplug is disabled. You have to remove the # to enable the command.
It sure is, I copied and pasted just to make sure the code was correct and turns out it wasn’t. I removed the # from both lines and now it’s working absolutely flawless.

Thank you so very much for the solution to my problem!

Doogals
Posts: 50
Joined: Sat Apr 02, 2016 8:55 pm

Re: HDMI Boot Sequence (10.1" LCD)

Fri Mar 30, 2018 6:15 pm

rpdom wrote:
Fri Mar 30, 2018 4:24 pm
There is a way around this. You can make the Pi read the monitor configuration from a file instead of from the monitor itself.
Also just FYI, I did first attempt to execute this command over SSH but was not successful. PuTTY first returned the result that sudo was not required when using LibreELEC, followed by “nothing copied” when executing the command without using sudo. I logged in using “root” and “libreelec” as the password, wasn’t able to see anything when editing config.txt either, but I am very new to all of this and mistakes are very likely. Thank you regardless for the quick reply and solution!

klricks
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Location: Grants Pass, OR, USA
Contact: Website

Re: HDMI Boot Sequence (10.1" LCD)

Fri Mar 30, 2018 7:34 pm

Doogals wrote:
Fri Mar 30, 2018 6:00 pm
klricks wrote: If the above is a Copy & Paste from your config.txt then hotplug is disabled. You have to remove the # to enable the command.
It sure is, I copied and pasted just to make sure the code was correct and turns out it wasn’t. I removed the # from both lines and now it’s working absolutely flawless.

Thank you so very much for the solution to my problem!
You should not take the # from the first line. That is just a comment. When there is a # then the rest of the line is ignored. Without the # the system tries to run it as a command which is isn't. That could lead to error messages or unexpected results.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

Doogals
Posts: 50
Joined: Sat Apr 02, 2016 8:55 pm

Re: HDMI Boot Sequence (10.1" LCD)

Fri Mar 30, 2018 8:09 pm

klricks wrote:
Fri Mar 30, 2018 7:34 pm
You should not take the # from the first line. That is just a comment. When there is a # then the rest of the line is ignored. Without the # the system tries to run it as a command which is isn't. That could lead to error messages or unexpected results.
So I’ve changed the comment that explains what “hdmi_force_hotplug=1” does (and also the examle of the command) into the actual command itself?

Does this mean the Pi is trying to execute a command to “Force HDMI even if unplugged or powered off” thinking that is now code?

So I should have just added “hdmi_force_hotplug=1” to the very bottom of config.txt correct?

Sorry for the basic questions, just want to understand correctly.

klricks
Posts: 6442
Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: HDMI Boot Sequence (10.1" LCD)

Fri Mar 30, 2018 9:47 pm

Doogals wrote:
Fri Mar 30, 2018 8:09 pm

Does this mean the Pi is trying to execute a command to “Force HDMI even if unplugged or powered off” thinking that is now code?
Yes
Doogals wrote:
Fri Mar 30, 2018 8:09 pm

So I should have just added “hdmi_force_hotplug=1” to the very bottom of config.txt correct?
You can put as many comments as you please to help you remember what the command does. Just make sure the first character is a #.
Though quite a few commands are obvious as to what they do, so no need to comment everything.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

Doogals
Posts: 50
Joined: Sat Apr 02, 2016 8:55 pm

Re: HDMI Boot Sequence (10.1" LCD)

Sat Mar 31, 2018 1:12 am

klricks wrote:
Fri Mar 30, 2018 9:47 pm
Though quite a few commands are obvious as to what they do, so no need to comment everything.
What is considered the “correct” location in config.txt for adding new commands? At the bottom under all of the comments?

klricks
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Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: HDMI Boot Sequence (10.1" LCD)

Sat Mar 31, 2018 1:52 am

Doogals wrote:
Sat Mar 31, 2018 1:12 am
klricks wrote:
Fri Mar 30, 2018 9:47 pm
Though quite a few commands are obvious as to what they do, so no need to comment everything.
What is considered the “correct” location in config.txt for adding new commands? At the bottom under all of the comments?
Not really a correct location. I put new commands at the end so I can easily find them. You have to be careful... Since the file is interpreted sequentially, if there is an existing command to turn something on and you add a command to turn that same thing off, but your new command appears above the exiting command then nothing is going to be changed.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

Doogals
Posts: 50
Joined: Sat Apr 02, 2016 8:55 pm

Re: HDMI Boot Sequence (10.1" LCD)

Sat Apr 07, 2018 4:07 am

klricks wrote:
Sat Mar 31, 2018 1:52 am
Not really a correct location. I put new commands at the end so I can easily find them.
I ended up replacing the # before the comment, and left the # omitted before the command, like so:

Code: Select all

#Force HDMI even if unplugged or powered off
hdmi_force_hotplug=1
Everything seemed to be working fine with the command on line 50, so I decided to leave it there rather than adding it to the bottom.

Thanks again for the help.

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