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An Autolaunching OPi Image Host For a Projector

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Post time 2016-4-21 12:32:09 | Show all posts |Read mode

I run a small AV rental company in Houston, TX. We rent PA systems, up lights, dance lights, projection gear etc. This past week, we produced a couple of shows for a stage magician. Among his requirements were to have two projectors in the front corners of the venue displaying the promo image for his act. Our usual approach to two identical projections is to feed an image/show from a laptop into one projector and then daisy-chain to the second projector or, if the distance is too great, to feed a splitter box and run two outputs from the spitter to the projectors. Because of the width of the hall, both solutions were impractical and it's a pricey proposition to to pick up an HDMI to CAT5 conversion system.

In comes the Pi. Since it is a static image, I figured that I could just use some image viewing software, point to the image file and run a separate pi at each projector station. On the surface, a pretty easy looking project.

Project goals:
The act is generally a one-man show. The talent is not computer savvy so it had to be totally automated - plug it in and let it go.
The system must operate completely standalone. boot up, autolog in, launch the viewer, display the image and not dim out in a power saving mode. No network is needed so the only connections would be power and video.

I did a bit of Googling and found a picture frame project by Gus at that uses feh as the image engine.

My first real complexity was that I decided to translate his project into use not on a Raspberry Pi but on an Orange Pi One and instead of running an "orange version of Raspian," it runs Ubuntu Mate. It took about 8 hours of on and off effort/trial and error. There was also a bit of a of challenge getting the thing to autolaunch.(rc.local turned out to be futile, as did crontab) but I finally got it going on Monday - five days before the show.

- note - I installed the same SD Card into an Orange Pi PC and it worked as well - note -

The next day, I pulled out an original Raspberry Pi model A. It never had acceptable XBMC/KODI performance and wound up sitting on a game room table for a few years. For this simple project, it seemed to be up to the task as far as specs go. It was running Raspian from 2013 so I started down the long road of update/upgrade. Of course, this would be a much quicker task since the project from Gus would match the Raspian settup, right? For want of a nail, the kingdom was lost. We'll get back to that.

So I ran through the project steps, added the autologin from raspi-config and gave it a test run. Unlike on the Orange Pi, I could not get a successful test from the command line - not direct entry to the terminal, not calling it from a bash script and certainly not executing it with a bash call from rc.local. Kept getting the same problem - unable to open X display. I'll look at it with fresh eyes in the morning.

Next day, I spent a bunch of time researching the error message but didn't find anything that was germane to my situation. I made so many changes that I figured I should cut my losses, blast the whole thing away and start up a fresh image. So, newest Raspian installed (post 3/18), I fired up Gus' steps again. And got the same result.

Can't be the image engine or the project process - I have personally made it work.
Not likely to be the OS - tried two different version of Raspian.
Could be the board? I have tons of Pis around to and can try another board but that didn't seem likely.
Could be the user? Almost surely. When I encounter a computer problem , it's usually mechanical (there's a nut loose behind the keyboard).
So, I started the project clean and did nothing from memory. When I got down to setting the display variable, there it was. I had been operating that line zillions of times with a faulty memory of what it was supposed to be. The line begins:


Somewhere along the way, I had dropped the ":" by entering "DISPLAY=0.0..."

So, for want of a ":" the project was lost.

Popped the colon back into place and abracadabra, alacazam, voila! She is finished.

Last problem was getting it to run per Gus' instructions about launching it from rc.local.

His code of "bash /home/ &" didn't have enough oomph behind it so a slight modification to:

su – pi -c ‘/bin/bash /home/pi/ &’ and all the goals were met. Total time and effort (on and off between "real" projects at work was another 8 hours!

When I first described my set up for the system, my talented magician friend did not have a clear picture of what I had in mind or of the Pi and how I would use it. He was kind of forced to accept my "trust me." And to be honest, I had a case of nerves and brought along a laptop to the gig in case I had to shell into a Pi for a fix or even to use it a replacement for a failed Pi. Fortunately, both Pis worked flawlessly. Whew! He was completely knocked out.

Now that it's a proven quantity, I will offer this as a service to my customers as the computer of choice for those events that have slide shows (brides and grooms love to have a display up of the couples pictures from childhood through the wedding day), videos and wherever else I can use it to source the projectors. Saves room and hassle of dealing with laptops, various video connectors and they're wonderfully compact and convenient.

(By the way, the LED display in the photo is an I2C board on the OPi One created by Jason Mann to display the IP Address of the Pi. He designed it for the Raspberry Pi.  I did some work to modify his installation to work on the Orange Pi and with his help, we got it working on both the PC and the One.  It's great for taking the thing out into the wild, picking up a DHCP address then quickly identifying it instead of running Angry IP or something to figure out the address. I know, there's always raspberrypi.local/orangepi.local as long as I'm running bonjour on the ssh client but the the IP Display is nice and quick and always right. FYI, we use them in classrooms when we have 6-12 PIs running simultaneously that start out with the same name.  This way all students know which Pi is theirs.)

Okay, back to the feh writeup:

The system met all of its project goals:
Simple power and HDMI connector
Power up, standalone, unattended operation
Auto launched into program and autoplayed the image (tested with directories full of images as well)
Continuous undimming operation

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