Simple and Small CNC Controller. Features are:

Hardware:

* Small form factor: 52x85mm (just the same as standard credit/debit cards are)
* 4 independent axes driven by TI DRV8825
* Configurable Motor currents (set by DAC in software)
* Configurable stepping mode (set in software)
* Isolated (ADuM4160) USB interface (enumerates as virtual com port)
* 8 limit switches are supported
* PWM 5V output for spindle control
* Probe input

Software:

* 50kHz update interrupt frequency
* Supports Linear Feed, Arc Feed (in both formats), Dwelling, etc.
* 9 coordinate systems
* coordinate offsets
* plane selection
* feed rate and inverse feed rate, all compensated for diagonal motion
* simple acceleration/decceleration profile
* Bresenham algorithms for line and arc motion (no segmenting)
* all fixed point arithmetic, no floats, no 'libm' functions