toozie21
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Joined: Tue Aug 06, 2019 10:44 am

Multiple VGA synced outputs

Tue Aug 06, 2019 10:55 am

I've searched around, but can't seem to find a post (or article elsewhere) that covers the sort of problem I am trying to solve. I have not bought a pi for this project yet (and maybe pi isn't even the right answer for the project), so I am not limited there.

Essentially for a Christmas display project I am brainstorming, I want to have a mix of a pair of projectors as well as some regular Christmas lights. The lights will be controlled via SSR, and need to be in sync (doesn't have to be too tight, milliseconds is MORE than enough) to the videos. The two videos themselves will need to be in sync with each other (again, sub-second is probably fine). The plan is to show about a 45 second clip on each projector that look like they are interacting with each other via the SSRs.

Since this is going outside, I have been looking at used projectors because I don't know how well this is going to work overall. Because of that, the projectors usually don't have Ethernet, USB, or HDMI. This means that I will need to display video to it over VGA or RCA.

I was trying not to break the bank on this (again I am not sure how well it will work yet), so I was trying to figure out if there was a way to use a single pi that had a script that kicked off both videos, and then controlled the SSRs via timing in the script (think simple sleep functions).

If it helps, the videos are actually pretty small. I am making them 320 pxl wide x 480 pxl tall, so I am by now means using the whole projector's image canvas.

Any thoughts? TIA

aBUGSworstnightmare
Posts: 1492
Joined: Tue Jun 30, 2015 1:35 pm

Re: Multiple VGA synced outputs

Tue Aug 06, 2019 12:33 pm

a Pi4 should be good for this. But, you will have to spend some money on adapters and cables.

toozie21
Posts: 3
Joined: Tue Aug 06, 2019 10:44 am

Re: Multiple VGA synced outputs

Tue Aug 06, 2019 1:38 pm

aBUGSworstnightmare wrote:
Tue Aug 06, 2019 12:33 pm
a Pi4 should be good for this. But, you will have to spend some money on adapters and cables.
OK, this at least gives me an avenue to start going down. I don't mind spending //some// money, I just don't want things to start to get out-of-hand, or I over complicate it (which I am good at). What kind of adapters are you thinking (not sure if you are thinking something oddball because of the two videos, two displays scenario?

At the end of the day, the answer might just be 2 pis, one for each projector, and have one of them kick of scripts on either side. I am not sure.

The VGA is going to be the sticky point I think.

aBUGSworstnightmare
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Re: Multiple VGA synced outputs

Tue Aug 06, 2019 2:04 pm

well even for a 'more than one Pi' scenario you will require some HDMI-to-VGA adapter solution.
For the Pi4 something like this (https://www.amazon.de/Audio-%C3%9Cbertr ... B00XWC5TX6) should do (not tested by me! Simply googleing for microHDMI to VGA); remember you will require two of them!)

Use the OMXplayer for playing your videos to the respective output (--display=7 (for HMDI1) or --display=2 (for HDMI0)). Some scheduler can do the 'stuff inbetween'

jamesh
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Re: Multiple VGA synced outputs

Tue Aug 06, 2019 2:48 pm

Here's a cheap and cheerful VGA adapter running off the DPI pins. https://www.aliexpress.com/item/32805339645.html
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hippy
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Re: Multiple VGA synced outputs

Tue Aug 06, 2019 3:16 pm

One should be able to simply plug in USB DisplayLink 2.0 adapters to get multiple VGA outputs.

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mikronauts
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Re: Multiple VGA synced outputs

Tue Aug 06, 2019 6:21 pm

Use two of those, on pi0w's to drive the projectors, with another pi controlling the relays and telling the 0s when to play
jamesh wrote:
Tue Aug 06, 2019 2:48 pm
Here's a cheap and cheerful VGA adapter running off the DPI pins. https://www.aliexpress.com/item/32805339645.html
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

toozie21
Posts: 3
Joined: Tue Aug 06, 2019 10:44 am

Re: Multiple VGA synced outputs

Wed Aug 07, 2019 12:32 pm

Thanks for the conversation, these ideas were exactly what I needed to help think of the different possibilities out there. I didn't realize how cheap the 0s were.

What I bought last night (knowing that I might need to make some minor mods, but that the 0s could be reused by other projects of mine) was a 0 and a 0w. My thought is to have them talk to each other over RS232 (I didn't want to use WiFi since the coverage might be spotty in my front yard. I also figured that I don't need a third 0 just yet as there are more than enough GPIO on the 0s for the SSR I need (again, I could add in an addition pi down the road if need be).

I also picked up the composite video breakout cable. I thought I could give that a try first since it was super cheap and the quality might be good enough for what I need. If I need better, I could go the mini-HDMI to VGA route.

Good call on the omx package. I'd never heard of it before, but it sounds a lot like what I need!

Any gotchyas that I've missed so far?

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