Here are the basic parts I plan on ordering. I will be able to load and run gcode and engraving files from an SD card, navagate through a touch screen, control 3 axis motors, control PWM laser power, and have a keypad for jogging around.
The motor controller will be an Arduino Uno (http://www.sparkfun.com/products/9950
). Price $30. This will be a dedicated controller and will do nothing but interpret and execute G-code through the GRBL open source controller code. There is plenty of flash ram space in here to add and modify the GRBL code to execute specific laser operations. You can directly connect this board through the USB port to a computer and set it up to stream G-code, but I don't want to do that. I want it to run off of a flash card independantly of my computer so there is no chance of it messing up once I set it up when it is running.
I will run a second controller, probably a Arduino Mega (http://www.sparkfun.com/products/9949
). Price $65. This component will be used for a few things:
1) When the laser is cutting, the sole purpose of this microcontroller will be to read G-code from the SD card and stream it to the UNO. If there is enough horse power in the system, it may update the touch screen with laser path progress or something like that. I doubt that this will be a problem given various buffering strategies I can impliment (that being, there shoudl be enough space on the UNO between the serial buffer and operational ram to store several hundred G-code lines ahead of what is being executed at any given time) so that should leave me some slack on the send side to do other things during cutting, but we will have to see.
2) During non cutting times, the microcontroller will be tasked with user input via the touch screen (file controll) and a 12 button keypad that will do jogging and such. I haven't decided what kind of data output or screen controll it will have.
3) it will connect to a computer via USB so I can load and unload files to the SD card without having to remove it.
The touch screen shield I plan on using is from nuelectronics (http://www.nuelectronics.com/estore/ind ... ucts_id=31
) for 29 GBP's (about $50).
I'm not sure about keypad/keyboard input, but this pad looks promising (http://www.sparkfun.com/products/8653
) it's $4.
I may ditch the keyboard and display in favor of a visual C++ program connected to the usb of the MEGA running on my laptop.