Melzi board use SPI pins for Z endstop


I have a Melzi board and use the Z min endstop pin for a leveling sensor, but would like to add a Z max endstop. There are no "free" pins available on the microcontroller.
Would it be possible to use the SPI pins (MISO/MOSI) for that? They are defined in the pins.h and seems to be used for something, but i'm not sure for what? (Besides programming, but that's only relevant during the bootloader stage, right?)

I tried redefining the MISO pin for z max endstop, but that didn't seem to do the trick.




  • SPI is used for sd card, so if you have it activated it will be initilized as spi pin and not all purpose pin.
  • good point, didn't think of sd card support. in the current dev version, I have it disabled anyways, as it doesn't fit on the micro if both display and sd card is activated.

    so I will try again, as I only experimented with the stable version last time.

  • Maybe a second avr connected through i2c.
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