Experimental Physics and
Industrial Control System

"J. Lewis Muir" <[email protected]> · Mon, 29 Nov 2010 09:12:58 -0600

On 11/28/10 11:57 PM, Angus Gratton wrote:
> Does anyone have any tips on simulating hardware for easy/quick UI
> development?
> 
> My intention is to be able to test that a given UI and a database talk
> properly, before facing the problem of having the database talk to the
> hardware. I'm using wxPython w/ pyepics for the UIs.
> 
> I've read about the 'simulation mode' record fields in the Record
> Reference & App Developer's Guide, but I don't just want to switch a
> single record over to simulation mode. I want to control a soft IOC
> without any of my real target hardware, but with equivalent PV names.
> 
> Have I missed an available resource somewhere?
> 
> At the moment I'm thinking the easiest way may be to just run sed over
> my database file to change all the DTYPs to asyn soft records (all our
> hardware records are asyn), and then fix up the INP/OUT port names. Then
> I can just poke in the values I need for UI testing at runtime, using
> iocsh or caget/caput.
> 
> Thanks in advance for any tips.

Hi, Angus.

For serial or Ethernet devices that have an ASCII communication
protocol, I usually write a simulator for the device in Python using
Python's asyncore and asynchat modules.  Then, I just change how the
ASYN port is created in my EPICS soft IOC and I can test any GUIs, EPICS
databases, etc.

For devices that are not easily simulated, I typically write a simulated
database for any database that would communicate w/ the device.  I might
name it the same as the real database but prefixed with "sim" or
something.  This approach is not as good because I don't get to exercise
the real database, and I have to make changes to the database twice:
once in the real one and once in the simulated one.  But sometimes this
is the best choice.

And then there are some things that are a real pain to simulate such as
records which have a special DTYP and no soft channel support.  Usually,
I end up doing something like the sed hack you mentioned where I
generate a simulated database from a real one.  Or, I write a simulated
database but with my GUIs and other clients designed to accept a field
separator character so that a reference like "ioc23:status.BI03" could
be replaced with one like "ioc23:status:BI03" where I simulated the BI03
status bit field instead with a bi record named "ioc23:status:BI03" in
my simulation database.  (BTW, in my view, this is one big plus for
databases composed of the standard records rather than special purpose
records: a database of standard records is a lot easier to simulate.)

Lewis

-- 
J. Lewis Muir
Software Engineer
IMCA-CAT

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System