RoboTrader
Posts: 18
Joined: Mon Nov 13, 2017 1:53 pm

How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 3:55 pm

Hello Pi-Fans,

I have a 7" LCD color monitor with 1440 x 234, PAL/NTSC, 16:9 in my camper and want to use it for my Raspberry Pi 3B+.
And I already have (the right) cable and connected it (composite video output of the pi to cinch input of the LCD).

First trial:
The blue stand-by screen changed to a black screen and I saw the boot lines with white letters but it was chaotic and blurred.

Second trial:
So, I decided to install the GUI (had only Stretch) and set the 16:9 option in /boot/config.txt but now I cannot see anything and it's just the blue stand-by screen like nothing is sent.

Could anyone help me with this wish?
Thank you!

drgeoff
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Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 4:30 pm

Are you sure the RPi is now booting? Red LED steady and green one flashing randomly for circa 30 seconds?

What happens if you reinstall the OS you began with?
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RoboTrader
Posts: 18
Joined: Mon Nov 13, 2017 1:53 pm

Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 4:51 pm

I am sure because I have another monitor and there I can see the booting and I can use it.
And in the camper I can connect by ssh local. So, it runs. But I cannot see anything on the LCD but on another monitor.

jamesh
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Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 4:52 pm

Is the Pi set to NTSC and the screen to PAL or vica versa?
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RoboTrader
Posts: 18
Joined: Mon Nov 13, 2017 1:53 pm

Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 4:58 pm

Hm, good question. In the specifications of the LCD it's written "PAL/NTSC automatic switch" ...

cleverca22
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Joined: Sat Aug 18, 2012 2:33 pm

Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 5:46 pm

i believe the composite output is disabled if hdmi is detected

on he rpi4, composite remains off by default and you need to enable it in config.txt

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mikronauts
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Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 6:01 pm

fyi, it is 1440/3 pixels as they count r, g, and b separately.
RoboTrader wrote:
Thu Jul 09, 2020 3:55 pm
Hello Pi-Fans,

I have a 7" LCD color monitor with 1440 x 234, PAL/NTSC, 16:9 in my camper and want to use it for my Raspberry Pi 3B+.
And I already have (the right) cable and connected it (composite video output of the pi to cinch input of the LCD).

First trial:
The blue stand-by screen changed to a black screen and I saw the boot lines with white letters but it was chaotic and blurred.

Second trial:
So, I decided to install the GUI (had only Stretch) and set the 16:9 option in /boot/config.txt but now I cannot see anything and it's just the blue stand-by screen like nothing is sent.

Could anyone help me with this wish?
Thank you!
http://Mikronauts.com - home of EZasPi, RoboPi, Pi Rtc Dio and Pi Jumper @Mikronauts on Twitter
Advanced Robotics, I/O expansion and prototyping boards for the Raspberry Pi

RoboTrader
Posts: 18
Joined: Mon Nov 13, 2017 1:53 pm

Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 6:22 pm

cleverca22 wrote:
Thu Jul 09, 2020 5:46 pm
i believe the composite output is disabled if hdmi is detected
on he rpi4, composite remains off by default and you need to enable it in config.txt
I uncommented the line `hdmi_ignore_hotplug=1`.
mikronauts wrote: fyi, it is 1440/3 pixels as they count r, g, and b separately.
Thanks. But I didn't set anything yet.

What makes me wonder is that I do not see anything?
And I did see anything before?

I have another SD and will set the clean Raspbian there to check it.
By the way, is there a clean way to uninstall the graphics installed before by:

- sudo apt-get install -y raspberrypi-ui-mods rpi-chromium-mods
- sudo apt-get install --no-install-recommends xinit

After remove those three packages, is everything like it was before?

Thank you all!

cleverca22
Posts: 2924
Joined: Sat Aug 18, 2012 2:33 pm

Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 7:06 pm

RoboTrader wrote:
Thu Jul 09, 2020 6:22 pm
cleverca22 wrote:
Thu Jul 09, 2020 5:46 pm
i believe the composite output is disabled if hdmi is detected
on he rpi4, composite remains off by default and you need to enable it in config.txt
I uncommented the line `hdmi_ignore_hotplug=1`.
that means it will ignore the lack of hdmi, and always force it into hdmi only mode!

you want to turn that off if you want composite

also, which model of pi are you on?, the 4 needs an extra setting to enable composite output

RoboTrader
Posts: 18
Joined: Mon Nov 13, 2017 1:53 pm

Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 7:17 pm

cleverca22 wrote: that means it will ignore the lack of hdmi, and always force it into hdmi only mode!
you want to turn that off if you want composite

also, which model of pi are you on?, the 4 needs an extra setting to enable composite output
I tested all variations.
Nothing worked.
That's so curious.

So, I have to set the '#' before the `hdmi_ignore_hotplug=1`.

And the other parameters are not really important, am I right? I at least have to get any signal - even a bad one, haven't I?

(Raspberry Pi 3B+)

cleverca22
Posts: 2924
Joined: Sat Aug 18, 2012 2:33 pm

Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 7:22 pm

and youve confirmed the composite signal is present and works on a normal tv?

drgeoff
Posts: 11559
Joined: Wed Jan 25, 2012 6:39 pm

Re: How to configure the composite video output to a 7" LCD?

Thu Jul 09, 2020 10:14 pm

cleverca22 wrote:
Thu Jul 09, 2020 5:46 pm
i believe the composite output is disabled if hdmi is detected

on he rpi4, composite remains off by default and you need to enable it in config.txt
The first line of the opening post contains "... and want to use it for my Raspberry Pi 3B+."

One "DL" is enough on these forums is sufficient, thank you. :)
Quis custodiet ipsos custodes?

RoboTrader
Posts: 18
Joined: Mon Nov 13, 2017 1:53 pm

Re: How to configure the composite video output to a 7" LCD?

Tue Jul 14, 2020 9:57 am

I am still trying with different images. Please, let this thread open. :)

I could only test the HDMI port with a VGA adapter because I do not have an adapter from the Raspberry Pi's composite video output to my VGA monitor.
So, I only can test it in the car and then add or change anything in my flat with internet.

RoboTrader
Posts: 18
Joined: Mon Nov 13, 2017 1:53 pm

Re: How to configure the composite video output to a 7" LCD?

Sat Jul 18, 2020 12:50 pm

I tried every configuration ... I do not even get anything on the LCD again.
As I wrote above, I had some hieroglyphs at first but now - even after setting up a completely new raspbian on another sd card, nothing works.
Any ideas, impulses, ...?

The LCD works. It has 2 inputs and one is the camera to the back in our camper. And I do see a blue screen (it's the screen when nothing is sent over this input) but this does not change. The cables are connected like they were in the first trial where I could see something. So ... I don't know.

Is there a possibility how I could test the composite video output with a multi meter?

Thanks!

hippy
Posts: 9212
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Location: UK

Re: How to configure the composite video output to a 7" LCD?

Sat Jul 18, 2020 5:40 pm

RoboTrader wrote:
Sat Jul 18, 2020 12:50 pm
Is there a possibility how I could test the composite video output with a multi meter?
Possibly, but if it's only showing mostly a black screen it won't be easy to say if it's working or just noise being picked up by the multimeter. A scope would be better but the usual 'poor man's test' is to simply plug it into a TV / display and it either works or it doesn't.

I suspect it's a configuration issue. The way I got my Composite Video working ( and an HDMI monitor which wasn't working on a PI but did on other things ) was to SSH/Telnet in from my desktop PC, adjust the config.txt, reboot and check what 'tvservice' and other useful commands reported. Keep trying until it worked, write the settings down, then start tweaking.

If you are in a state where you don't really know where you are it might be worth re-flashing the SD Card, configuring that for some kind of composite out, which will hopefully get you back to where you were, composite working albeit not very well.

If you only have an LCD monitor in the vehicle which makes things difficult, you can try it through your TV, video player, or borrow a portable TV from a friend. You could consider a long phono lead out to the vehicle just to get something shown.

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