Experimental Physics and
Industrial Control System

Torsten Bögershausen <[email protected]> · Mon, 9 Feb 2015 06:30:06 +0100

I'm not sure if we need to change anything in drvAsyn at all.

The Python script can be started by inetd (or similar).

Whenever StreamDevice on the IOC connects to the port on the machine with the

Python script.

(Both can be on the same machine, or on a different one)

When the Python script is started, it will have stdin/out/error connected to

the socket.

I haven't tryied it yet, but this looks promising:

https://en.wikipedia.org/wiki/Inetd

On 06/02/15 14:51, Dirk Zimoch wrote:

Hi Christian

At the moment, StreamDevice cannot do this directly. The 'exec' command can
only pass parameters to an external program but cannot pipe data into the
program or read its output, nor can it evaluate the exit status.

But it would be a nice exercise to write an asynOctet driver that uses a piped
program instead of a serial line.

drvAsynPipeConfigure "myProgramPort" "program arg1 arg2 arg3 ..."

The driver may restart the program whenever it has exited and asyn tries to
talk to the port again (i.e. autoConnect).

Any volunteers?

Dirk

On 05.02.2015 17:58, Christian Pauly wrote:

Hi

I want to read out a little pressure sensor, for which i have already a
small python script which reads the sensor (via i2c bus) and prints the
sensor value to the terminal. Alternatively, i could also give the
sensor value as return value upon program exit.

Now i want to read this sensor inside an EPICS IOC.
Is it possible, to use StreamDevice for this, by calling the external
script / program and evaluating the return value ?
Maybe using the "exec" statement in the protocol file ?

Reading the sensor takes some time (500ms), so it would be good to do it
asynchronously, without blocking the IOC.

Or is there any other easy way, without reimplementing all the i2c
sensor readout eg inside an ASYN driver in C++ code ?

Thanks for any hints or help

Best regards,
Christian

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System