Problem with "last" LED of a 10-Plasma buttons array


I own a picade 10 inch arcade box, and upgraded it at the end of February with 10-Plasma-buttons. After installing them, I found out that 2 of the 10 PCBs did not work correctly (some of the LEDs did not function) and one of the cables had some issue too, all the PCBs after the defective cable did light up only 1 LED in a random color…
so i replied to the reseller, and he kindly sent me a new set of Plasma Buttons.
now I have the problem, that the last LED in the complete chain always reacts with a delay, or does even nothing.
for example, when I set plasmctl 64 64 64, all buttons light up white, when I switch to plasmactl 0 0 0 - then all lights go out, except the last LED in the chain - it always remains blue… sometimes, after a while it goes out too, sometimes it keeps lighting blue. (I’ve uploaded a small video of the “effect”)


I already was spending hours in changing every single cable and every single PCB and trying different combinations, but the behavior stays the same. so I’m running out of ideas… could possibly the picadeHAT itself be the problem?

I’m using a raspberry Pi4 with an original raspberry power-supply,
the latest version of Raspbian and RetroPie.

thank you very much for your help,
kind regards,

This won’t help much but I’m pretty sure the Hat doesn’t factor into it. The Pins used for the plasma LEDs are just passed through to the Pi. GPIO 14 (pin 8) and GPIO 15 (pin 10)
I don’t own a Picade, and have only ever run Plasma on my Blinkt, which uses 8 LED’s
I edited /usr/bin/plasma and changed LIGHTS = 10 to LIGHTS = 8. The default is 10 so you shouldn’t have to change anything.
Your Issue might actually be the second last LED. Maybe its not passing the correct signals on to the last LED. Each one has an In and Out connection. Try swapping the positions of the last two in the chain or replacing the second last one with a spare if you have one.

hi alphanumeric,

thank you for the fast reply. as mentioned in my first post, I already swapped out every PCB and every cable systematically (and spent hours with “swapping” parts) - I actually have 16 “working” PCBs and 2 sets of cables, and whatever I change, the error remains on the same last LED (so it can not be one of the PCBs physically, because the error is remaining on the same LED, even when swapping out the whole bunch of PCBs and cables).

…but you brought me to an idea - you mentioned the “LIGHTS” count in the plasma “binary” - I changed it to 12, which doesn’t really make sense, but with that setting, even the last LED goes out instantly, when sending “plasmactl 0 0 0”…

the big question is now, why it doesn’t, when “LIGHTS” is set to 10?

best regards,

That I don’t know? When I did my Plasma install it lit up the LED on my fan shim, which is just the one LED. The Fan Shim LED uses GOIO 14 and 15. I had to edit the plasma.service file and change it to GPIO 23 and 24 for my Blinkt, which has 8 LED’s. I could have just left it at 10 Lights but decided to change it 8. I didn’t really notice any change. It would be hard to see anyway with a constantly changing pattern. At 8 all 8 LED’s work just fine though.

hi again,

I spent some time on testing this weekend and came to the conclusion, that the issue seems to be in the plasma script itself. I swapped some of the cables and PCBs again, and then I tested around in changing the amount of “LIGHTS” in the plasma script - when I change the “LIGHTS” for example to 6, then the last LED of the 6th PCB shows the effect described in my initial post, when I change it to 8, then the 8th LED shows the strange behavior… so I changed the “LIGHTS” to 12 now, and it runs fine… maybe this will be fixed with some of the next updates.

it would be interesting, if someone else could reproduce the same effects, or if this happens only on my system.

best regards,

I’m not seeing any issue on my Blinkt, even with lights set to 8. The colors cycle through the last LED. I don’t have a Picade or your light setup to test though.
I will turn Plasma back on latter today and play around with the lights setting to see what happens if I go to 7 or 6 lights.

hey, thanks for your fast reply, the question is, how the “Blinkt” compares to the Plasma PCBs, one PCB has 4 individual LEDs, so I think you should see the error only when you set “LIGHTS” to 2 or 1.
the best way to see it in my setup is to send for example “plasmactl 128 128 128” and then “plasmactl 0 0 0” - then the last LED in the chain remains lighting blue, sometimes it goes out after a while, sometimes it stays lighting blue.
when cycling colors, it seems to react normal.

For the Blinkt each element is a 3 LED array. Red Green Blue. There is no dedicated fourth White LED like some of the NEOPIXELs have.
My setup is in my bedroom on my spare dresser (media hutch) at the moment, so I have to wait for my wife to get up before I start lighting up the room lol.
I will try what you have suggested when I get the chance. Likely a few hours from now.

Changing to Lights=4 didn’t have the effect I was expecting?
They all still lit up. The color pattern likely changed but it was hard to tell.
plasmactl 155 155 155 got me all white and
plasmactl 0 0 0 had them all turn off.

the question is, how does it react when you change lights to 2 or 1 - because one PCB of the 10 in the Plasma array has 4 “Groups” of RGB LEDs, so I think 4 RGB Arrays are one “LIGHTS” in the plasma binary.

I was assuming because I had 8 (RGB) LED’s in the Blinkt I should use 8? One RGB LED is one LIGHT.
If I set it to LIGHTS=1 only 4 light up. So I guess its as you stated? They all turn off with plasmactl 0 0 0 though.
I set them all blue then off with no issues, and all white and then all off with no issues.
Then set LIGHTS=2 for my 8 LED’s and did the above again and all good.
I have no idea why your having the issue your having?