Maximum single neopixel length

General Discussion
1

Basic Information:

Printer Model: voron 2.4 wip
MCU / Printerboard:btt octo 1.1

Describe your issue:

heya, new here and trying to get neopixels set up on my printer. from the poking around i’ve done i haven’t seen any specific mention of a limit to “chain_count” in any of the documentation, or in any posts my google-fu can dig up. looking through the klipper github i found that in neopixel.py there is a line that describes a max chain length.
MAX_MCU_SIZE = 500 # Sanity check on LED chain length

i have a strip that is 138 pixels long connected to PB0, any value higher than 125 for chain_count gives me the klippy error “neopixel chain too long”

quite puzzled, any advise?

1 Like
2

A RGB Led is using 3 addresses, a RGBW is using 4.
So I assume you have a RGBW chain: 4 x 125 = 500

3

and indeed, bumping the MAX_MCU_SIZE to 552 fixes the issue.
thank you very much for your prompt and apt observation. I hadn’t even thought that that would make a difference.

4

Hi @missmillie, how did you change the MCU size in the .py file? Is there a simple way to change it instead of actually forking the repo and building my own copy of klipper?

5

oh, i used nano over ssh.
it makes my install of klipper “dirty” but so far I’ve just been putting up with it and redoing it when i update. I’ll figure out a more permanent solution at some point.