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Settings in a customized firmware doesn't work no matter how I change it

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Hi friends,

Please help! I cannot make my settings in the customized Marlin firmware work. Here's my story:

I'm using a UM2. I was going to change the


parameter to make the fast forward length shorter, otherwise I found the filament was reaching the nozzle at a very high speed, which constantly causes heavy filament grindings.

So I download the source code from the official github: ultimaker2marlin, found the file UltiLCD2_menu_material.h and changed the


in the file from





Then I compiled the firmware by following the knowledge I've got so far: with Arduino, commenting out the


part in twi.c, compiled it and uploaded the .hex file by using Cura 15.04. I was sure for the successful firmware update because I saw the version changed to my customized one in the LCD menu.

But the forward length seemed not changed at all. Grinding happened as before. So I changed FILAMENT_FORWARD_LENGTH to (Bowden_length - 150). Again, no visible difference was shown. The fast filament feeding still went like nothing was changed.

To understand what was happening I used G-code G1 E-100 in printrun, and measured the outgoing filament. I found the outgoing length was almost 200mm, twice as it should be! I thought that might be the reason, perhaps every length was doubled, therefore even (Bowden_length - 150) were still longer than the actual length of bowden tube because of this doubling!

I thought the reason for doubling was the wrong setting in the configuration.h: I found the DEFAULT_AXIS_STEPS_PER_UNIT for extruder was 282, which I thought should be 125 or so since I had a φ8.1 feeder wheel (if I did the math right). Then I changed it to 125, expecting the 100mm feeding length instead of 200.

But after uploading my changes, nothing changed. The G-code feeding G1 E100 (or -100) is still 200mm filament in output.

So it turns out nothing have changed no matter how I was tweaking the settings in Marlin. So I'm totally confused! Did I did something silly? Does anyone use a customized firmware? Any clues will be appreciated ! Thanks!



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Thanks very much! That's exactly what I'm looking for!


So  - you changed the default settings and compiled it into your firmware. That's not wrong, but those settings are stored in eeprom and can be changed via gcode commands.

The new defaults will only be used after a "Factory reset"...


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