adding a limit switch to mmu idler axis
Hello,
I'm gauging the feasibility of adding a limit switch to the mmu2s idler axis. The motivation is to use it for the initialization procedure. This would get rid of the ramming sound on startup and consequently prevent the loosening of the axis screws over time due to the vibrations.
Is there an unassigned digital or analog input on the mmu2s board (2019-09 rev 0.4.4, sheep edition) which one could use for a limit switch?
Regards
Matthias
RE: adding a limit switch to mmu idler axis
there's a 6 pin I2C/SPI that remains unused in normal operation. I don't believe that this will allow an endstop to interface directly, at least without additional components in between but that's the only available port without hacking one into the circuit somewhere. The SOC can surely handle it anyway. You also have the firmware to program an endstop into. I have not looked at the MMU2 firmware but maybe the framework for an endstop is already in there and commented out. It would not surprise me.
RE: adding a limit switch to mmu idler axis
This person has implemented it. Check the photos.
https://www.printables.com/model/45226-mmu2-pinda-idler-endstop
RE: adding a limit switch to mmu idler axis
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RE: adding a limit switch to mmu idler axis
TZB firmware eliminates the startup "ramming" and in my experience tames some of the idiosyncrasies of the MMU2. It gets confused about its state a lot less and when it does it recovers and moves on without a lot of fussing with it. It also implements on-screen messages about the MMU2 so you are not dependent on the LED codes. It's a small-resource developer from what I can tell so the base Prusa firmware is not the most current but that is not important to me with my MMU, I just want it to behave. Final point - I can not tell you the last time I had to push the reset button on the MMU board since switching to the TZM firmware.