problem homing all axis

Hi everyone,

I am very new to the reprap scene so please forgive me if my questions seem stupid.

I recently bought a prusa mendel from DX.com (link here)

building it went well, everything went together fairly easily despite the included instructions being for a completely different extruder and bed (these two sections conveniently came assembled so this was not a problem). Installed the equivalent of arduino bootloader for the melzi board and then the Marlin firmware.

Now i can control movement in all axis directions. Some of them were the wrong direction when i first tried so i changed the following

#define INVERT_X_DIR false    // for Mendel set to false, for Orca set to true
#define INVERT_Y_DIR true    // for Mendel set to true, for Orca set to false
#define INVERT_Z_DIR true     // for Mendel set to false, for Orca set to true

and then I ran into my problem. I am using repetier-host and when i try to home any of the axis they do not run until they hit the switch and then stop. It simply moves a little then stops or doesn't move at all. It would appear that the position value is just set to 0 on the computer (without the head moving).

I checked switch states with none touching using M119 and got this response:

x_min:H y_min:H z_min:H

I also checked the switch states when i was holding the y axis switch down:

x_min:H y_min:L z_min:H

1. any ideas how i can get the print head to home correctly.
2. should it automatically home on power on ?

Edited 2 time(s). Last edit at 07/06/2014 04:12PM by slzer.

Have you tried inverting the end stops in the firmware? Set them to the opposite of what they are now and try again.

const bool X_MIN_ENDSTOP_INVERTING = true; // set to true to invert the logic of the endstop.
const bool Y_MIN_ENDSTOP_INVERTING = true; // set to true to invert the logic of the endstop.
const bool Z_MIN_ENDSTOP_INVERTING = true; // set to true to invert the logic of the endstop.

Marlin won't automatically home when turned on.

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**SOLUTION**

there is some incompatibility with Marlin and the Melzi board I am using. I switched to Sprinter instead. Worked immediately!