Saturday, December 5, 2009

I/O ??? LPPT#1 ??? Parallel Port??

Lets talk about how the PC communicate with the muscle.

In natural language, The PC is the brain and the stepper motor system is the muscle.

In this specific case, the Intel D945GCLF mobo, is the PC talk to the CNC machine?

To simplify the analogy, lets leave the EMC2 software system, the mechanical structure, mechanism, electrical ...etc out for the moment.

The PC, has a choice to send and receive signals via serial port, USB and parallel port. with EMC2, the choice is the parallel port.

Traditionally, the parallel port is used as the printer port, there are 25 pins which are arranged as per the table attched, can do 8 bi-directional ports, 4 output ports and 5 input ports.

The simplest way to connect the machine & the parallel port is directly via a cable. BUT because the signal strength from the parallel port is not strong, interfering noise can have its way with the signal & the corrupted signal my be of no meaningful use. or if the receiving end is passive or require some "drive" to work properly.
since my Stepper Motot Driver/Amplifier requires about 15mA to function properly, Hence, a buffer stage is used, normally this is made into a separate PCB which are called Break-Out Board or BOB.
I use a PMDX-122 board which I was mislead into buying. You can find plenty of board at half or less price with equivalent of better specifications. Or maybe DIY one for yourself for less the USD10.

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