Re: Question about the best practice for integrating a stepper motor Python library into EPICS

[Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>]

When I said client/server I meant was Python opening the socket to the hardware, or listening for a socket connection from external software.  I see it is the former.

I think that porting to C++ will be a lot easier.  You only need to implement a few methods:  move(), moveVelocity(), stop(), home(), poll(), etc.  There are lots of example drivers to use as models.  We can help you find the one that is the closest match to your system so you have a good starting point.

The asynMotorController and asynMotorAxis base classes and the asyn device support take care of most of the details of interfacing to the motor record.

Mark

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From: Alexander Kessler
Sent: Thursday, May 11, 2023 9:46 AM
To: Mark Rivers; tech-talk at aps.anl.gov
Subject: Re: Question about the best practice for integrating a stepper motor Python library into EPICS

Hello Mark,

Yes, it is a TCP Connection to HW.

'''

import socket

s = socket.socket()
timeout = 1.0

s.settimeout(timeout)

s.connect(host, port)

'''

Well, it's a P2P connection, I think client-server is not the right term here. I would say Phyton Code is the master, says that to do it, and HW is the slave.

No EPICS so far. I'm trying to make a device driver IOC from Python Lib. Because I am complete beginner, I want to ask for the better way to do it. I see two options:

1. port to C++
2.  create in Python a PV interface according to the motor record. https://epics-modules.github.io/motor/motorRecord.html
   The module motorVMC seems to do something like this.
   
   https://github.com/epics-motor/motorVMC.git
   

Best regards,

AlexK

Am 11.05.2023 um 14:30 schrieb Mark Rivers:

Hi Alex,

• I have an in-house built stepper motor controller and a python library to control it. 
• It simply opens a TCP socket, sends a command bytecode and queries some state bytes.

Do you mean that the Python library opens a socket to the controller and sends a command bytecode and queries bytes from the hardware?

Or do you mean that external software (like EPICS) opens a socket to the Python library and sends a bytecode?  

In other words is the Python library a socket server, or a socket client?

If the Python library is a socket client then how complex is it?  It might just be easier to replace it with a C++ asynMotorController that sends the bytecode and parses the response.

Mark

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From: Tech-talk on behalf of Alexander Kessler via Tech-talk
Sent: Thursday, May 11, 2023 5:44 AM
To: tech-talk at aps.anl.gov
Subject: Question about the best practice for integrating a stepper motor Python library into EPICS

Dear community,

I have an in-house built stepper motor controller and a python library
to control it. It simply opens a TCP socket, sends a command bytecode
and queries some state bytes.
I would like to include the Python code in EPICS as my first productive
EPICS exercise. In C++, I would take EPICS engine module and create a
child class of asyncMotorControler.  But what is the best way to handle
it with Python? Is there an equivalent to C++ parent class on CAPROTO basis?

Thanks and best wishes,

AlexK

--
Alexander Kessler

Helmholtz-Institut-Jena
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phone:    +49-3641-947296
fax:      +49-3641-947299
email:    alexander.kessler at uni-jena.de
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-- 
Alexander Kessler

Helmholtz-Institut-Jena
Fröbelstieg 3, 07743 Jena
phone:    +49-3641-947296
fax:      +49-3641-947299
email:    alexander.kessler at uni-jena.de
web:      http://www.rlp-ioq.uni-jena.de/
          http://www.hi-jena.de

Facility for Antiproton and Ion Research in Europe GmbH (FAIR GmbH) GSI Helmholtzzentrum für Schwerionenforschung GmbH Planckstraße 1, 64291 Darmstadt, Germany, www.fair-center.eu, www.gsi.de

Commercial Register / Handelsregister:
FAIR: Amtsgericht Darmstadt, HRB 89372
GSI: Amtsgericht Darmstadt, HRB 1528
Managing Directors / Geschäftsführung:
Professor Dr. Paolo Giubellino, Jörg Blaurock Chairman of the GSI Supervisory Board / Vorsitzender des GSI-Aufsichtsrats:
Ministerialdirigent Dr. Volkmar Dietz