bigcrater
Posts: 17
Joined: Sat Apr 14, 2018 2:53 am

dual monitor; use each screen to display 1 output each

Thu Jul 22, 2021 8:54 pm

Ahem!! I'm convinced that I do not know the proper terms for what I'm talking about.

Pi 4, two monitors. The monitors are not the same physical size.

Code: Select all

uname -a
Linux jupiter 5.10.17-v7l+ #1403 SMP Mon Feb 22 11:33:35 GMT 2021 armv7l GNU/Linux
Both monitors are working -- I can set different backgrounds, etc., for each.

I'd like HDMI-1 to be the traditional monitor.
I'd like HDMI-2 to show the output of a program. In this case, it's one based on the opencv
library. Ultimately, I'd like to turn on the 2nd monitor with a relay (I know how to do that) and
run the opencv program, such that the output shows up kind of like a warning sign. I'll handle
the screen content -- I'm convinced that I can get my program to display what I want it to.
What I can't presently do is get my opencv program to open the ... what would it be?
the second monitor? second framebuffer? or do I have the opencv program run and simply
put the opened window in a specific place on the screen/desktop? I don't know how to do
that.

aBUGSworstnightmare
Posts: 3472
Joined: Tue Jun 30, 2015 1:35 pm

Re: dual monitor; use each screen to display 1 output each

Fri Jul 23, 2021 5:39 am

Jupiter? Which platform do you work with? It's not a Raspbian OS, isn't it? Make sure to update/upgrade as it's for sure not the latest kernel

User avatar
rpdom
Posts: 19044
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: dual monitor; use each screen to display 1 output each

Fri Jul 23, 2021 6:03 am

aBUGSworstnightmare wrote:
Fri Jul 23, 2021 5:39 am
Jupiter? Which platform do you work with? It's not a Raspbian OS, isn't it? Make sure to update/upgrade as it's for sure not the latest kernel
"jupiter" is the hostname. Not all Raspberry Pi systems are called "raspberrypi" ;)

"5.10.17-v7l+ #1403" looks like a standard Raspberry Pi 32-bit kernel, although I believe #1421 is the current build.
Unreadable squiggle

aBUGSworstnightmare
Posts: 3472
Joined: Tue Jun 30, 2015 1:35 pm

Re: dual monitor; use each screen to display 1 output each

Fri Jul 23, 2021 10:38 am

rpdom wrote:
Fri Jul 23, 2021 6:03 am
aBUGSworstnightmare wrote:
Fri Jul 23, 2021 5:39 am
Jupiter? Which platform do you work with? It's not a Raspbian OS, isn't it? Make sure to update/upgrade as it's for sure not the latest kernel
"jupiter" is the hostname. Not all Raspberry Pi systems are called "raspberrypi" ;)

"5.10.17-v7l+ #1403" looks like a standard Raspberry Pi 32-bit kernel, although I believe #1421 is the current build.
I see, thanks! :oops:

Code: Select all

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 5.10.52-v7+ #1 SMP Fri Jul 23 09:50:12 CEST 2021 armv7l GNU/Linux
This is the kernel build from latest sources (on a CM3 this morning). Don't remember what May 7th official image reported before installing the new modules.

OP needs to use latest sources as these have a HDMI hot-plug detect feature included. Old Feb image will need to have the monitors connected on boot, or with a forced resolution in config.txt at least.

bigcrater
Posts: 17
Joined: Sat Apr 14, 2018 2:53 am

Re: dual monitor; use each screen to display 1 output each

Sat Jul 24, 2021 8:25 pm

(I'm the OP.) Doing the upgrade now.

Any recommendation on what s/w I should consider?
I know about opencv, which is probably what I'll try first.

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