+Peter van der Walt yes. That would do it.
Yes Friends, after comment out the i2c stuff grbl-lea works w/o Problems on a c3d mini. Very nice. Here the compiled firmware:
https://github.com/xpix/grbl-LPC/blob/feat/laserk40_c3dmini/build/firmware.bin?raw=true
Many Thanks to +Peter van der Walt and @Todd_Fleming .
Woohoo! @Ashley_M_Kirchner_No please test this new one.
@Frank_Herrmann @raykholo It works for me! Although homing(error: undefined) and laser do not work, but at least the axis moves and I can connect with LW4 without problems. Axis move backwards but that seems like an easy fix. Is it too difficult for the average person to compile this fw with the changes such as the 2.5 for laser PWM? THANKS!
Right right. I forgot that Claudio had compiled a special version for me (and then it didn’t work because of this i2c bit). Yeah we need PWM going to 2.5, a default period of 200 (or 1/200 is the frequency) (and this can be changed later via a $ command). The other question is whether we can set up homing to max in grbl as this is the case for the Y axis. But a lot of these other things like axis invert are $ config command after the fact.
Pretty excited! +Peter van der Walt I’ve used Arduino quite a bit, but not familiar with compiling with LPC. I would like to learn, maybe there is a guide somewhere. I will search. Just don’t want to screw it up haha.
I’m afraid to put up toolchain install instructions because toolchains under Windows tend to conflict with each other (Cygwin vs. Mingw vs. Mingw64’s 100 varieties vs. the 100’s of subsets of Mingw that git’s installer and other installers spread across the filesystem). If I put up instructions, they’ll break someone’s system.
I do create such instructions at work, but those instructions start out with: uninstall A, B, C, D, E, … then delete directory I, J, K, … then remove environment variable L, M, N, …
So, clean install Windows or start up a VM and do it Todd’s way. I’m game.
@raykholo I’m actually running my K40 with a SBase board and grbl-lpc (self compiled version I sent you) and everything including homing to xmin/ymax is working.
I will do the i2c fix and send you a new version when I get to it.
@cprezzi I was interested in how to configure grbl to home to Ymax such that it would know it is at position (0, 200) when homed. I did not see any $ config references to this parameter.
Grbl always homes to 0,0, but you can add a G10 L2 P1 X0 Y-200 after $H to the homing Gcode in the Gcode settings of LW4.
Cool, agreed. Need to keep the WCS origin proper to not incur Peter’s wrath.
@cprezzi Please send me too 
thanks!
Yeah!
Ok, here in this instruction you can see how the laser mode works: https://github.com/gnea/grbl/wiki/Grbl-v1.1-Laser-Mode, first you switch M3 S1000 on and every G1,2,3, Move will switch the laser on. Ok, i will make a hangout with @cprezzi this week and we can check his changes on GRBL for an C3D mini and can publish a version and config that will run on C3D K40.
@Todd_Fleming you can write an instruction to compile a version on cloud9: https://ide.c9.io/xpix/grbl-lpc It’s very easy, you get a docker /ubuntu space and it’s possible to install ur toolchain and install some packages via apt-get w/o touch ur windows machine. Just my 2 cents
https://github.com/gnea/grbl/wiki/Grbl-v1.1-Laser-Mode
Yes, a docker will be cool!
Hi, so after some chat’s with @cprezzi here his and my changes for c3d mini, he add also a new command $33 to control the PWM Frequency directly. Maybe someone will test this on his c3d? Here the Firmware: https://github.com/xpix/grbl-LPC/blob/feat/laserk40_c3dmini/build/firmware.bin?raw=true
My fork with the $33 param for setting PWM frequency and defaults for K40 is on https://github.com/cprezzi/grbl-LPC
A pull request to the original grbl-LPC is allready running