On 07/14/2017 07:14 AM, Bertho Stultiens wrote:
On 07/14/2017 01:26 PM, andy pugh wrote:
Maybe some other developer can pitch in and say something about I/O
scheduling as currently implemented in LCNC?
EPP Parallel port works well for Pico and some Mesa cards. I don't
think IO data throughput is actually any real concern.
The throughput should be fine, but what about the latency?
I've measured this on a Pentium 4 at 2 GHz or so, and with
RTAI jitter is about +/- 5 us, with preempt-rt it is more
like +/- 10 us. preempt-rt has a possibility of scheduling
the servo thread via an external interrupt, but it would
take some changes to the rtapi, which is likely above my
skills. This would reduce effective jitter to sub-ns
levels, as all of our hardware can sample the encoder
position via a hardware timer that then triggers an
interrupt on the PC. Someday, I'd like to make that work.
Jon
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