On 10/19/2017 07:08 PM, andy pugh wrote:
On 19 October 2017 at 23:58, Chris Albertson <[email protected]> wrote:
OK you might argue that USB3 can be faster then Ethernet. Faster bit
rates but who cares, for this use case latency matters more then any other
spec.
Indeed, the EPP parallel port works splendidly for the Pico and (some)
Mesa cards.
The total payload every mS is a few dozen bytes.
Yes, on a 1 GHz Pentium 4 class CPU, with a generic parallel
port, the ENTIRE servo thread for 4 axes takes about 150 us!
This requires a handshake (in hardware) for every byte
transferred. So, it is about 50 us for the read of encoder
counts, 50 us for the PID calculation and then 50 us to send
the new velocities to whatever (servo or stepper) is in use.
Jon
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