Lost on LAN line

[cncmachineguy]

Thanks for the in depth reply Henrik. I had to laugh at myself when you did the math for me, that is usually my first thing when looking at others stuff. It has been brought to my attention the 20Us is WAY faster then I need. I will be very happy at 40, and could live with 60. Does that help things any?

[HenrikOlsson]

Hi Bert,
Sure it helps. Doubling the cycle time cuts the amount of data per time unit in half so you're going from 400kB/sec to 200kB/sec or 133kB/sec if you go to 60us - so yes, it helps. If it's doable? I still have my doubts and as I said earlier you still have to get the PC to spit out the ethernet packages fast enough. It's not just a matter of the bandwidth, you've got that covered, but since there is no buffer your 4byte packages must go out with exactly 40us between them. And again, your not sending just those 4 bytes of actual data - there's much more to it than that.

I've done some reading and although there's a LOT of variables having an impact on performance I found some numbers in section 8.0.2 of this document. They mention a possible cycle frequency of up to 25kHz on a 2GHz system which puts it right on your 40us mark.

I hate being sceptic but in this case I am (but please proove me wrong will you!). Like I said earlier, the servo-setup where velocity updates are being sent at ms intervals would be easier.

/Henrik.