On 2020-06-05 10:16, Chris Albertson wrote:
On Fri, Jun 5, 2020 at 9:58 AM N <nicklas.karlsso...@gmail.com> wrote:
USB should be able to handle real time but think it is complex which might
be a reason to avoid it and there are no support in Linuxcnc.
Mixing USB into RT kernel space is not something I would recommend due
to it's purpose and position in computer architecture.
Andy posted a clear example that shows a simple way to move data from USB
to LinuxCNC.
https://emergent.unpythonic.net/01198594294
Read the Python code that you find by following the above link.
Technically this is easy. Now to think about what a user should see on
the hand controller and how he should interact with it.
I currently don't have hardware to test this possibility. What came to
mind is software tool I use for troubleshooting message passing or
transferring bytes across local or remote sockets:
netcat sometimes linked as nc
Backup example:
----- server
cat backup.iso | nc -l 2222
----- client
nc serv_host 2222 > backup.iso
or
----- server
dd if=/dev/hdb7 | gzip -9 | nc -l 2222
----- client
nc serv_host 2222 | pv -b > hdb7partition.img.gz
pv - monitor the progress of data through a pipe
Socket is a file in Unix so you could put it into command above like this:
dd -if=<here> | nc -l 2222
and connect to it from other systems.
I think e-stop is a desired feature but it will never be as reliable as one
that is wired to the machine that does not depend on computer software.
Right, that should be wired to physical switch/relay to drop power to
most if not all CNC electronics in case of emergency.
USB does have a short maximum cable length but it should work. The
example linked above would work for WiFi or BlueTooth too. Once you see
how it works the method of communication is unimportant, you are simply
setting and reading HAL pins from userspace.
5G technology under development is going to be one of the best ways to
solve this issue. However, it's wireless implementation will be
sensitive to interference.
There are however a lot of cheap development boards available which may
make it a very cheap and good choice. There are standard protocol for
keyboard and mouse but do not know about this kind of input you want.
Switching noise might be a problem if connected to power electronics but
not to hand held device.
There is Modbus available in Linuxcnc. It might be a little bit slow
nowadays but expect it more than good enough for buttons. Think it is also
simple and no problem to build a device using one of these development
boards available but otherwise a Modbus Remote IO Module might be a good
choice.
Emergency stop, any plan for this?
--
Rafael Skodlar
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