Re: [CAD_CAM_EDM_DRO] Re: CNC Pulse jitter?

Patrick Mendiuk wrote:

> Jon,
> I'm sure lots of folks are getting very smooth motion with EMC both with
> stepper and servo. It torques me off about those big glitches, but I'm sure
> it's some kind of hardware/software drug interaction...
>
> The pulse generator scheme sounds very promising. I assume there is another
> EMC module to utilize external timing?

I'm not sure what you mean, here. There is a 10 MHz crystal oscillator on the board.
It generates the reference for timing, and can also set the "servo" update interval,
although EMC doesn't use this at present. If I can figure out how to make the
RT scheduler schedule a task based on an interrupt other than the interval timer
on the motherboard, then I can rig this to interrupt the CPU. It can also latch
the encoder counts and strobe the DAC (or rate generator) values to them
at the same time. This reduces jitter to the parts per million level, and is how the
"big guys" like Allen-Bradley do it.

> BTW Mr PulseRateGenerator could easily roll his own timing analyzer for this
> app with a Xilinx FPGA.

Yes, that's a thought I have had, too. I actually built a time stamp device for a
customer of mine. Using a similar circuit, maybe with the clock turned up a bit,
it could deliver a 48-bit grey code value to a latch on every step pulse, and
I could then read that into a logic analyzer for storage and then send it to a PC
for analysis.

Jon