Re: [CAD_CAM_EDM_DRO] Pin out for EMC

Rick Miller wrote:

> Hi,
> I was wondering how parallel port pin assignments are handled in EMC. Are the assignments configured by the user, or is there one set way of connecting it? I've seen two different versions on the web, and I'm wondering which one (or both?) is/are correct.
> I'm hoping to combine step & direction of 4-axis + controls for 2 relays on one parallel port, but I'm wondering if this is going to be possible...

With the stock EMC, it is not possible. The reason is that the stepper control
is done through a real-time process running under the RT subsystem of (RT)Linux.
The auxilliary I/O is done through a linux process running under the normal
Linux kernel. These programs communicate through shared memory or RT
fifos (depending on RT-Linux version). Since they expect complete control
of their own parallel port, they can't accept interference by another program
messing with 'their' parallel port. I have made changes in EMC to allow
the RT section to handle ALL I/O for the non-rt auxilliary I/O because my
parallel port motion control boards need to all talk through the same parallel
port. It was quite complicated, but since I have already done it, it could be
used by someone else for similar purposes. It would probably require some
changes in the stepper output routines so they won't touch the control
bits you are using. I will be putting my changes into the source forge
distribution sometime this month, I hope.

Jon