Re: [Emc-users] CANopen over Ethernet CiA 309 --> Ethercat seems to work

[John D. <jo...@au...>]

One of the reasons I am asking is that my Electronic Lead Screw controller
has a spot for a CAN bus driver.  Years ago I ported the Microchip CANopen
stack to it and had it serve as a minimal keypad/display and MPG encoder.  I
also built a small expansion board for the ELS that can stand on its own if
I put in a processor.  I also ported the CANopen stack to that board and
have had it as a CAnopen device that responds to SDO and PDO messages.  It
has 4 relays, 4 opto inputs and some voltage/current measuring capabilities.
So I have the infrastructure to run stuff.

I started working with CAN bus in 1992 so the idea of expanding a PC using a
simple USB to CAN dongle for tool changer and other controls is really
attractive to me.  With CANopen or what one might call almost a minimalist
CANopen one could add simple robot arms to place and remove parts to be
machined.  None of this requires Ethernet or centralized control.  Often
it's as simple as READY/REQUEST/BUSY/AVAILABLE/ERROR handshaking that used
to be done with wires in the PLC days.  

The device sits in ready, gets a request and sends back a busy to
acknowledge the command.  Once the command is complete it sends an available
or an error.  

I'm a big fan of modularizing things so that they can be tested in a
standalone fashion.  But how to turn an M code into a CANopen message is, at
the moment, beyond me.

John


> -----Original Message-----
> From: Nicklas Karlsson [mailto:nic...@gm...]
> Sent: February-24-18 1:10 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] CANopen over Ethernet CiA 309 --> Ethercat seems
> to work
> 
> > But if 99% of the devices out there are physical CAN bus based and there
is
> > already a CANopen driver for Linux,  is the interface to CANopen
> transparent
> > for both systems?
> 
> CiA309 should be transparent for both systems but are probably of less use
> for an ordinary CAN bus but to access the hardware bus some extra
> hardware is required.
> 
> It seems I got SDO communication up and running via Ethercat according to
> CiA 309 but I have not yet tested write access only read.
> 
> > What I mean, and I may not be clear on this, is if the LinuxCNC has the
> > capability of being a CANopen Master then how do you see your code
> handling
> > both bus architectures?   Or should it?
> 
> It is an Ethercat master but messages sent follow CANopen.
> 
> > ...
> > From the G-Code (M07) perspective the Pump On results in the periodic
> PDO
> > 0x287 to have Bit 3 in Byte 1 set.   An M09 would turn off both mist and
> > flood so Bits 2 and 3 would be cleared.  The PDO message could be
> periodic
> > or periodic and on change of state for faster response.
> 
> Periodic I consider good in a real system and it also have the advantage
> broken cable could be handled.
> 
> > So I guess I'm asking how does an M07 become either (or both) an
Ethercat
> > CANopen  message and/or a physical CAN bus CANopen message?
> 
> In the Ethercat master I added hal pins, some are bits connected to a bit
in
> sent messages. This configuration should ideally be possible to do in
> configuration file and templates for standard communication profiles would
> certainly be useful if available.
> 
> I found the simple_test program in soem lack a gnu GPL copyright notice
and
> are waiting for confirmation E-mail from github before I could upload.
> 
> 
> Regards Nicklas Karlsson
> 
>
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