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Author Topic: Software stops mid opperation.  (Read 543 times)

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Offline reuelt

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Re: Software stops mid opperation.
« Reply #20 on: March 15, 2019, 08:06:29 AM »
ethernet or USB are serial devices. So their frequency is quoted in bits per second and NOT bytes per second. So their real frequency will have to be divided by at least 6 (if only just 3 axis used) when comparing to the parallel port speed because parallel port is transferring one byte of 9 bits in parallel and not 9 serial bits one bit at a time.
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Offline ZASto

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Re: Software stops mid opperation.
« Reply #21 on: March 15, 2019, 11:09:09 AM »
Instead of onlky writing that Mach3 is faster and outperforms TCP/USB external controllers with parallel port, please give us some proof in NUMBERS/TIMING/bps/Bps....
And also, ask Art about that. His Auggie runs perfectly well with 57CNC :)
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Re: Software stops mid opperation.
« Reply #22 on: March 15, 2019, 11:12:35 AM »
Hi,
you misunderstand what is transmitted to an external controller. Your contention would be correct if an
external controller were simply a serial to parallel converter, but it is not.

Machs trajectory planner produces time slices of numeric data describing P(osition)V(elocity) over T(ime).
The controller then decodes the numeric data and using timers produce pulse streams in parallel.

The ESS uses 1024 time slices per second, near as dammit 1ms per slice. The packet of data will contain 4 bytes per
axis, for all six coordinated axes and another six Out-of-Bamd axes, for a total of 48 bytes per packet.
1024 packets per second for a total of 48kByte/sec. Note this includes the motion data only, various other IO
may increase it, but not that much. A ballpark figure is 60kByte/sec.

That (numeric) data is expanded into to pulse streams, lets say for arguments sake you have a three axis machine
with one OB axis, the spindle operating in Step/Dir mode, each with a motor tuning of 10,000 step/unit and the current
coordinated move requires all three axes to move ten units per second.
Each of the moving axes will require 100,000 pulses per second or 100 kBit/sec. If the spindle is required to rotate at 1200 rpm
(20 rev/sec) it will require 200,000 pulse or 200kBit/sec.
The combination of the three axes and the spindle will produce 500 kBit/sec of pulses in four simultaneous pulse streams.

The point here is that the pulse output rate is derived and determined by a much smaller, slower numeric data stream.
An external motion controller might receive its numeric data in serial packets but it produces independent parallel
output pulse streams which can be many orders of magnitude higher than the numeric data rate.

Note that Machs parallel port operates in an analogous fashion. PVT data is passed to the Ring0 pulse engine from
Machs trajectory planner, and ordinary Windows application. The pulse engine then generates the pulse streams.
Each independent output has a maximum output rate equal to the kernel speed. For the example above the parallel port
could  produce the required pulse streams  with a 100kHz kernel speed, but it couldn't go any faster and as you have pointed
out parallel port kernel speeds of 100 kHz are the exception not the rule.

Craig
« Last Edit: March 15, 2019, 11:17:53 AM by joeaverage »
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Re: Software stops mid opperation.
« Reply #23 on: March 15, 2019, 11:23:58 AM »
Hi,

Quote
For the example above the parallel port
could  produce the required pulse streams  with a 100kHz kernel speed, but it couldn't go any faster and as you have pointed
out parallel port kernel speeds of 100 kHz are the exception not the rule.
Sorry, my contention that a 100kHz kernel speed parallel port could run our hypothetical machine is wrong.
The parallel port could produce the 100kBit/sec pulse streams to each axis but NOT fast enough for the spindle
as it requires a 200kBit/sec pulse rate.

Craig
My wife left with my best friend...
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Offline ZASto

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Re: Software stops mid opperation.
« Reply #24 on: March 15, 2019, 11:59:35 AM »
Craig my post was directed to @reuelt.
Make no mistake between my personality and my attitude.
My personality is who I am.
My attitude depends on who you are.
Re: Software stops mid opperation.
« Reply #25 on: March 15, 2019, 02:56:31 PM »
Hi ZASto,
I guessed that, my reply was to reuelt as well.

Craig
My wife left with my best friend...
     and I miss him!