Download and install piLagTester for the Raspberry Pi Zero

The piLagTester is a simple DIY device for measuring input lag, using parts that cost $5-10. It's easy to set up since it uses a Raspberry Pi Zero board with zero hardware modifications or any additional parts beyond the normal pi0 accessories. Probably all pi3 and lower will work, but I've not tested that. The Pi4  is definitely not supported, however, due to some dumb choices they made about direct access to the onboard LED.

In order to guarantee the timing is correct I'm providing a custom OS image with the software included and ready to go with no additional configuration. The OS image happens to be the same one as used by the piLagTesterPRO, so that I don't have to maintain multiple OS images and all the required storage.

The direct link is:  email me for link

To install this to a 4gb (or larger) micro SD card you'll need to unzip it and then to use an app like win32diskimager, rufus, or equivalent. The raspbian official download page goes into the details so I'll skip them here.

Once written to SD card you can put it in your pi0 and turn it on.

No password required (but it's root/t if you need to know). Consider this encouragement to not have it on the network, since you get tighter timing that way.

All the software lives in /x, which happens to be in the path too. The main executable is inputLagLED

As it's part of the piLagTesterPRO distribution (an advanced version that requires custom hardware) there's other stuff in the /x folder that's not of much use to you, but in particular all the scripts that start with tv are useful for setting the resolution that you will test:

/root #ls /x/tv*
/x/tv1080i  /x/tv240p  /x/tv480p  /x/tvcea  /x/tvnative
/x/tv1080p  /x/tv480i  /x/tv720p  /x/tvdmt


That's it. Next up: time to use it!

Comments

herr ernst said…
This is a very good idea and a great realisation! Would you mind posting the source code generating the video (at least for the DIY version, not the pro)? Thank you!

BTW, it's not necessary to run piLagTester as root if your user is in the group `gpio` and you disable the led before: `sudo sh -c 'echo none > /sys/class/leds/led0/trigger'`.
April 30, 2021 at 10:26 AM
Alan Robinson said…
I found that timing was a little tighter as root, which is why I go that route.

no plans for posting the code at the moment. wouldn't be hard to replicate, though.
May 12, 2021 at 7:48 AM
herr ernst said…
Oh, I understand, then I also better run it as root.

For me, it's impossible to replicate the code as I don't know how to program something like that ;-)
May 12, 2021 at 8:09 AM
Alan Robinson said…
This code would be a good place to start, very close to the metal so it should have good timing:

https://github.com/alanbork/kmsmodeline
July 12, 2021 at 1:50 PM
Alan Robinson said…
FYI if you tried to use an earlier version of this that was just the executable tarred up and couldn't get it to work with your already installed copy of piOS, I've switched to using a complete SD card image, sidestepping any dependencies or configuration issues.
January 3, 2022 at 11:08 AM
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