Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Mon, 10 Sep 2012 10:45:24 -0500

Hi Florian,

On 2012-09-10 Florian Feldbauer wrote:
> 
> Up to now the driver support in EPICS is only synchronous. Is there any
> documentation on how to program an
> asynchronous driver support? For some other devices we would need an
> asynchronous support.

While I second Mark Rivers' suggestion that you consider converting your code 
to become an Asyn Port Driver, if that doesn't prove feasible you might want 
to take a look at my driver for the TEWS Tip810 IP module.  It's basically a 
vxWorks driver for the PCA82C200 CAN interface chip (supporting the raw CANbus 
protocol only), and some generic CANbus device support.  The latter gives 
asynchronous support for most of the standard record types with I/O Interrupt 
support, and even on-demand processing of output records in response to an RTR 
message (I don't know if that kind of thing is possible through Asyn).

You can find the documentation and tar-files for this driver at
    https://svn.aps.anl.gov/trac/epics/ipac
Look under the specific version link there for the documentation, and in the 
drvTip810 directory in the tar-file for the source code.

This code is released under the LGPL, so you're free to modify and re-use say 
just the device support part if you wish, as long as you include the source 
code if you distribute copies to anyone else.

Information on how to write asynchronous device support is spread around a 
bit; there is some text under the individual record types in the record 
reference manual on the EPICS Wiki but that isn't very comprehensive.  There's 
a bit more detailed description in the Device Support lecture from the latest 
USPAS course, see http://www.aps.anl.gov/epics/docs/USPAS2010.php and finally 
there's a chapter on Device Support in the Application Developers' Guide which 
may also help — the code examples there are getting a bit old now, but should 
still work.

HTH,

- Andrew
-- 
Never interrupt your enemy when he is making a mistake.
-- Napoleon Bonaparte

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System