Hello Elliot,
just to elaborate a bit more on the previous messages:
- we run about 1000 power supplies via can-bus
- when we started this 15 years ago, we deliberately did not use
a higher-level protocol like can-open to keep things simple and
to get more devices on one loop. Over the years, we adapted
Andrew's driver to also work with PMC modules, but I agree with
Andrew that this is not the solution you are looking for.
- in order to avoid the problems Burkhard's problems, we
developed "hub"-boards, which daisy-chain the CAN-bus and
individual CAN controllers are fed from them by short
stub-cables, effectively introducing a local star-topology at
the hub.
- the advantage of this is that we can take individual
controllers off the bus without breaking the daisy-chain
- the disadvantage: this is not a clean solution, but it works
because we run the CAN-bus at a relatively low speed of 100
kHz.
- rolf -
On 3/16/2011 8:17 AM, Andrew Johnson wrote:
Hi Elliott,
On Wednesday 16 March 2011 09:19:29 Rod Nussbaumer wrote:
We use CANbus extensively to control beam optics power supplies. These
are controlled mostly from VME CPUs using the Tews vxWorks and more
recently Tews Linux driver, with EPICS device support from Andrew
Johnson's package.
The Tews driver and CAN device support are included with my drvIpac module,
but are designed for raw CANbus packets using Basic CAN only; the device
support doesn't speak any higher level protocols such as CANopen, and the
driver can only talk to the Tews Tip810 IP module. I haven't followed
developments in CAN since I wrote it well over 10 years ago, and after reading
your description I would not recommend trying to use this for your new
development.
Also, is the ASYN framework the best choice if we have to develop a new
driver?
Something based on Asyn would probably be the best starting point for future
work, as it supports connecting to TCP, UDP and serial devices out of the box.
- Andrew
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