Let me go back one step and outline my idea.  First I have machinekit running 
on a BBB with a Xylotex Cape that has a DB-25. There are some problems with the 
high verses low for switches NC/NO so I ended up not using it.
 
I'm not directly thinking of the MachineKit, LinuxCNC or MACH3/4 group of 
users.  I'm thinking of the users who don't even sign onto the CNC groups and 
aren't interested in CNC.  Often because they don't know what they don't know.
 
What I'm thinking of is an ELS-MILL that has DROs, Step/Dir signals, Spindle 
Speed control, and ideally spindle speed feedback along with the usual group of 
inputs and outputs like limit switches and coolant etc.
 
Really just a DRO setup with power feed on each axis.  For someone using a 
manual mill the addition of power feed to an axis is such a tremendous 
improvements and there are all sorts of ways of doing this.  Model Engineer's 
Workshop magazine etc all have had articles along that theme.
 
Now grab that laptop or PC neither of those have SPI or IIC at least not 
without an add on card of some sort.  But they pretty well all have Ethernet.  
So BBB, Pi, PC, Laptop embedded PC box all with LCD Display or HDMI, USB for 
keyboard and mouse all running some form of CNC software with the motion 
commands out Ethernet to a target.  
 
And if that target is the ELS-MILL (which serves as a Break out Board too) then 
you can easily migrate a non-CNC user to the wonders of CNC.  And if you use a 
BBB or Raspberry Pi running machinekit in a way that appears to be an ELS-MILL 
but with a local/remote switch changes personalities you now have it all 
bundled into one board.
 
But that might be asking too much hence the idea of using a PIC32 or something 
like that for the ELS-MILL.
 
John
 
 
From: [email protected] [mailto:[email protected]] On 
Behalf Of justin White
Sent: March-02-20 5:56 PM
To: John Dammeyer
Cc: Machinekit
Subject: Re: [Machinekit] Re: PICnc with Machine Kit.
 
Yeah, there is no reason to use ethernet when almost everything has a uart. SPI 
is a viable rt interface and there is no reason to tie up the processor boards 
ethernet port. Mesa is using spi with the raspberry pi boards, the 7c80 and the 
7c81, so you are pretty much guaranteed it works. Also being that spi comes off 
a gpio header there is no rj45 connector to add to the pic card.
 
I'm lost on the USB-c talk.....an rt interface is about transferring small 
packets quickly. USB regardless of the generation isn't required, or even 
really suitable. Mesa doesn't even use gigabit on its ethernet cards, its 
10/100.
 
I've never heard of this PICnc before now but it seems like it could have been 
a good idea but that micro was too small, and imo too slow. Step rates were 
only mentioned at 40khz which is OK I suppose but mesa is doing them at 10mhz 
on a spartan 5/6. Stepgens and encoders only wind up running at a fraction of 
the speed of the controller and a 40mhz pic32 seems to get 40khz, while a 
500-600mhz fpga is getting them at 10mhz.
 
I realize cost is a thing here but what is the price difference really between 
the original pic32 used and a higher end micro?
 
On Mon, Mar 2, 2020, 7:16 PM John Dammeyer <[email protected]> wrote:
A bit of digging through my boxes after a double check of the data sheet shows 
I find that the PIC32 won't serve my needs.   I thought it had a quadrature 
encoder module but it doesn't.   I have PIC32MX boards and a bunch of dsPIC33F 
series boards.  
 
The problem is the PIC32MK which has motor control features and the quadrature 
encoder doesn't do Ethernet. However one could add the ENC28J60 to deal with 
Ethernet if it was wanted for connection to a MachineKit, LinuxCNC or MACH3 PC. 
 Or just use a Pi or Beagle running MachineKit or LinuxCNC and SPI and forget 
about Ethernet connectivity.
 
I have these modules.
http://www.autoartisans.com/PIC32/AutoBoard_CAN_EEROM.jpg
http://www.autoartisans.com/PIC32/PIC32_Sets.jpg
 
And a bunch of others with dsPIC33F series modules.
 
This will require some more research…
John Dammeyer
 
 
 
 
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