@jbsapp
Great information.

I was curious and managed to locate a little detail on the fuzz and other arguments.

https://stackoverflow.com/questions/16110515/explanation-of-fuzz-and-flat-in-input-absinfo-struct-in-input-h

You can find that

fuzz: specifies fuzz value that is used to filter noise from the event stream.

Which means that the input system in linux will drop events generated by the device driver if the difference from the last value is lower than the fuzz. This is done in the input layer.

Another user posted:

So it would seem that any changes less than fuzz are should be filtered out / ignored.

Also,
https://python-evdev.readthedocs.io/en/latest/apidoc.html
The Device section talks about the fuzz argument.

@mitu Cool, thanks! That puts my mind at ease.

@jbsapp Unfortunately, no. I stopped searching for a solution after awhile, since it doesn't bother me that much. Actually, I came to appreciate that the beautiful Comic Book Theme is shown from time to time this way.

A friend of mine who is an electrician suggested to short-circuit the port in question by sticking a piece of wire in both sockets. I never got around to do this unbelievably complicated operation, though. 😇

@cyperghost thanks will check that link out!

I switched everything round, loaded up a random playstation game (2002 Fifa World Cup) and hit various hotkey combos (save state, load state, retroarch menu, exit emulator) a few times. All seemed to work without issue. The main test will be a longer play with testing throughout so will see how it goes.

Yeah, the onboard BT of the rpi3b is total crap. I didn't test it but i heard onboard BT is better on rpi3b+

@lex3001 Please excuse the question, but are you really sure about the ghost inputs only happening in the Arcade menu? I ask because It sounds rather strange. Did you wait long enough in all of the menus to rule out mere coincidence of it happening only in the Arcade menu?

You can test a controller for ghost inputs out of Emulation Station by pressing F4 (you'll land in Retropie's command console) and entering this command:

jstest --event /dev/input/js0

Any inputs coming from the device will be listed while the command is running. You may have to change js0 to the device name of your controller, e.g. js1, js2 etc. You can end the test by pressing ctrl+c and return to Emulation Station with the command exit.

As for solutions for ghost inputs from bluetooth controllers, I fixed those that came from my Qumox Wii U Pro controllers by using a Mayflash Wii U Pro wireless adapter instead of the Raspberry Pi's own bluetooth to connect them. That got rid of the ghost inputs for good.

@mediamogul No, the joysticks have digital microswitches. I noticed an error in my reasoning: The buttons have nothing to do with the problems, as their ports are generating type 1 events. Only the joystick ports on the decoder board (four for each joystick, one per microswitch) generate type 2 events.

That said, the joysticks' microswitches are connected to the ports for axis number 0+1, whereas the ghost inputs only come from axis number 2, which nothing is connected to.

I tried to set the dead zones of axis 2 on both joysticks to its whole range of -32767 to 32767, hoping that would lead to the driver ignoring them alltogether. After that, jstest doesn't show any input from them anymore, but the screensaver still recognizes some input in irregular intervals and quits back to ES.

$ jscal -s 7,1,0,127,127,4227201,4194176,1,0,127,127,4227201,4194176,1,10,-32767,32767,2147483647,2147483647,1,0,127,127,2147483647,2147483647,1,0,127,127,2147483647,2147483647,1,0,0,0,2147483647,2147483647,1,0,0,0,2147483647,2147483647 /dev/input/js0 $ jscal -s 7,1,0,127,127,4227201,4194176,1,0,127,127,4227201,4194176,1,10,-32767,32767,2147483647,2147483647,1,0,127,127,2147483647,2147483647,1,0,127,127,2147483647,2147483647,1,0,0,0,2147483647,2147483647,1,0,0,0,2147483647,2147483647 /dev/input/js1

The part for axis 2 is 1,10,-32767,32767,2147483647,2147483647, see jscal's manpage for more information.

I got this idea after some research, from these two sites:

https://ubuntuforums.org/showthread.php?t=1079284 (a similar problem to mine) https://blog.gimx.fr/joystick-calibration-in-gnulinux/ (it explains the working of jscal -s in some more detail)

Its a mess...
after trying numours installations i cant fix it. The issue is too annoying too look over. Im done.

@pjft
My power settings are the stock settings.
I think this is what happens: When the boxart image size is large, the Pi needs a bit of time to load the image. This causes a slight delay when scrolling from one game to the next. Other controllers ignore this, but the DS4 seems to remember the directional button input during the delay and keeps it going, without me having to press the button anymore.
But yes I am very glad I found the solution. Thanks for your input, as you asking me if specific games were causing this, got me on the right track.

@tropez I have ghost inputs from time to time. But mine are a little more tame, a random scroll to the right or left. If I power down and back on, that usually does the trick.