Re: PC to controller comunication protocols

Gentlemen:

I too have been working (off and on) on a CNC controller. It is DOS
based with a max step rate of 4.166 KHz. It does work well, but I'd
like to have available a higher step rate, and a smoother output
pulse train. The current max pulse jitter is 240 microsec.

I've been working on an external curcuit which accepts commands of
up to 31 steps from the parallel port and does linear interpolation
in X, Y, Z from the sequential commands. The base update rate is 1
KHz, so there's time for the computer to do other tasks such as
velocity smoothing and cutter comp. My current IC external circuit
has added "noise" pulses at the rate of about 12 or so per 100,000
pulses, not acceptable. So far I have not eliminated the noise. The
supporting PC program for the above with linear and circular
interpolation is done, and appears to be OK. The objective for the
new approach is 31KHz pulse rate and a jitter of 30 microsec or less.

If I knew something about programming microprocessors, they would be
a better possibility, as the code to handle linear interpolation for
3 axes is simple, in BASIC anyway. My programming experience has
been only in QuickBASIC.

I'd be quite interested in communicating with others of similar
interests. A spec sheet and screen view of my controller are
available. I could post them in the files and photos section here.

Regards,
Jack C.