Embedded Microcontroller based Computer Numerical Control

https://code.google.com/p/gocupi/ Code for Arduino and Raspberry Pi with nice acceleration curves and turn prediction. The Arduino is only there to
provide precise timing for the step and direction pulse data produced by the Pi. Motion is smooth and fluid because the entrance and exit speed of each movement segment is taken into account. E.g. A 90' turn needs a full stop, but a 1' turn doesn't need to
slow down at all.+
https://github.com/ErikZalm/Marlin/tree/Marlin_v1 This RepRap firmware is a mashup between Sprinter, grbl and many original parts.+
http://www.hwml.com/LeibRamp.htm LeibRamp was developed in 1994 by Aryeh Eiderman and is said to be the "World's fastest ramping (motion profile building) algorithm." On this page, Eiderman provides an overview
of the math involved in calculating pulses per timer tick, for slew, and ramp acceleration / deceleration.

http://www.hwml.com/ is an NXP LPC2136/01 based USB to 4 axis embedded motion controller in a DB25 backshell. $75 from:

http://www.mcwidgets.com/

http://read.pudn.com/downloads45/sourcecode/embed/151169/Motor.c__.htm Demo program for stepper motor control
with linear ramps. Hardware: PIC18F252, L6219. The discussion of the method and the math behind it may be found here:http://fab.cba.mit.edu/classes/MIT/961.09/projects/i0/Stepper_Motor_Speed_Profile.pdf+

http://code.google.com/p/cnc-milling-machine/ Open source, Java G code to intermediate format, PIC firmware 2axis coordiantion with seperate Z axis movement. No acceleration.

http://www.planet-cnc.com/index.asp?page=diy G code to propriatary format in PC software $100 then by USB to 4 axis motion control hardware $15 for the PIC chip, $15 for the PCB and about $15 shipping.
The PIC firmware does NOT actually process G code.

http://forums.reprap.org/read.php?12,9459 Arduino G code to stepper. See user.cpp file.

+
https://github.com/simen/grbl Grbl is a free, open source, high performance CNC milling controller written in optimized C that will run on a straightArduino+

https://www.synthetos.com/webstore/index.php/assembled-electronics/grblshield-grbl-arduino-diy-cnc-shield.html a shield is available

http://pleasantsoftware.com/developer/3d/pleasant-mill/ Another mill with firmware based on the reprap.

http://www.cnczone.com/forums/open_source_controller_boards/59461-full_cnc_controller.html

http://www.usinages.com/controleur-autonome-de-cnc-t2415-75.html

MicroBasic pic18f4620, SD-MMC card, KS0108 graphic LCD. Direct G code to movement. Bugs in circles but can be avoided. Clunky source.

http://www.roboticsguy.com/projects/build-a-cheap-diy-cnc-machine Very simple design that works for drilling.

http://reprap.soup.io/post/135633178/Smooth-Trajectory-in-CNC-and-3D-Printing Some notes about smoothing motion.

http://www.massmind.org/techref/io/embeddedCNCs.htm