From: dan...@austin.rr.com
To: "Les Newell"
Cc:
Sent: Wednesday April 10 2019 1:33:31PM
Subject: Re: [Emc-users] Hardware emcmot?
From: "Les Newell"
To: "Danny Miller"
Cc:
Sent: Wednesday April 10 2019 12:55:14PM
Subject: Re: [Emc-users] Hardware emcmot?
Moving just emcmot is not really practical but moving the whole
realtime
side to another processor shouldn't be too hard. If I remember
correctly
the CMS/NML communication subsystem already has network
functionality.
Of course in that case you'd probably need your external processor to
be
running some sort of Linux.
Les
On 10/04/2019 17:10, Danny Miller wrote:
> I have been wondering- can emcmot be separated from the HAl and
> emctask and become a true dedicated realtime stage to control the
joints?
>
> The shared memory FIFOs could be replaced with like an ethernet
link
> to the hardware RAM. You'd probably load a DMA buffer and just let
it
> flow, there's some minor latency but there's not a realtime
requirement.
>
> There are cheap high freq MCUs with single-cycle hardware double
> multiply/add and gobs of memory. It would have to be coded in
non-OOP
> C and I greatly prefer hardware interrupt-driven strategies over
RTOS.
>
> Danny
-----------------------------------------
Actually I *don't* want to run a form of Linux. Since it's dedicated
HW, the tasks can be hardcoded for bare metal and stored in flash and
directly load the STEP/DIR pins with SPI data which does precise,
synchronized step-outs.. This is leaner, simpler, more reliable and
the latency can be very low and consistent (although LinuxCNC on
Preempt-RT is already all of that for my machine).
This would require somewhat extensive modification of code.
Microcontrollers typically use C and cannot handle C++'s OOP nor
dynamic memory allocation. However, static mem allocation should be
fine and, like I say, faster and lower latency. Converting objects to
non-OOP code is usually pretty straightforward.
Danny
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