It's a dead easy way to get effectively GPIO control of pins and if run in a single-tasking operating system (ie DOS) you get completely deterministic timing. The Parallel port is used because it's ever present and very cheap. Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT I know we have several people on the forum who are into the CNC arena more than I am so I am eager to learn if this idea has been tried or if there are other reasons that the Parallel port is used. There would have to be a protocol for sending an instruction or set of instructions out the usb/serial port, having the micro execute them and then ask for more from the PC. Thus anything created would be target to one specific software or platform, unless they were all open enough to incorporate a driver to send commands over usb/serial. The problem with just creating it is that there doesn't appear to be a protocol for communicating. In fact it could be as simple as a 'smart' usb/serial to parallel port driver. The device wouldn't have to be expensive or complicated. However I could see a serial or USB micro to parallel port device being a good thing to open up the computers that can be used for controlling the CNC machine.
For a home CNC person they don't want to have to learn some other complicated device or pay for it. I understand that the parallel port is used as digital I/O to make the stepper drivers move or to get feedback from a switch input, but why not use serial or USB and put a simple microcontroller in between the PC and the stepper driver? For home CNCing you want to keep the smarts in the computer because computers are cheap and easily available. Now, we have all read the articles and forum posts with lamenting at the lack of serial ports on computers, but aren't parallel ports heading down the same path? Over the weekend I was reading the latest Make Magazine and it occurred to me that so many CNC drivers and software programs rely on the parallel port. I have had an interest in home manufacturing and CNC for a while.
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