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Subject: Re: EPICS training information
From: Pierrick Hanlet <pmhanlet@gmail.com>
To: Mohamed Chaouechi <chaouechimed92@gmail.com>, "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Fri, 13 Oct 2017 14:35:10 +0100
Dear Mohamed,
I won't answer your questions point by point, but here is my simplistic description; I hope that
you will find it helpful.  Mind you, this is my simplistic description; the real EPICS guru's may
correct my misunderstandings.

EPICS is a framework from which you can create a control system; please refer to the attached
cartoon.  Any control system will have a number of hardware devices; e.g. cyro pump, power
supply, high voltage supply.  Each of these hardware devices have a number of parameters;
e.g. current, temperature, voltage, On/Off, which are used to monitor and/or control the hardware.

In order to be a part of a control system, each hardware device must communicate with one,
or more, computers over some interface; e.g. RS232/RS485, TCP/IP, SNMP, Modbus, etc.
using some drivers.  The drivers are usually provided by the manufacturer.  EPICS allows
you to write an IOC (Input/Output Controller) which uses these drivers for communication with
your hardware device.  Within the IOC, you create PVs (process variables) and these are
representations of the hardware's parameters (current, temperature, etc).  Each PV is created
from a "record"; e.g. analog input, binary output, calculation, long integer, sequence, subroutines,
etc., which are provided by the EPICS framework.  Each PV also has a variety of "fields"; e.g. scan
rate, alarm limits, upper/lower operating limits, engineering units, etc., which further describe the PV.
Not all PVs represent hardware parameters.  PVs can interact with each other and be used to
control each other. 

Once your IOC is running, EPICS provides interfaces and tools to use the PVs.  The IOCs live on
an local area network (LAN) and with proper permissions, other processes on the same LAN
can access them.  Some of these tools are GUIs, archivers, alarm handlers, or gateways to access
other networks.  These clients usually access the PVs via "channel access".  When a process
searches for a PV, it sends out a broadcast message via UDP.  When the IOC which owns the PV
recognizes this request, a TCP connection is made between the client and IOC.  Note that IOCs
can act as clients to other IOCs.

So, EPICS is the framework plus tools.  It handles interrupts, timeouts, connections, etc.
EPICS is open source software, so it's free.  It does not require any hardware; your computer
can be a linux box, windows box, raspberry pie, VME crate, android phone.  There are no
proprietary components.

I hope that this is helpful.  Good luck to you.  By the way, from which institution do you come?
Pierrick




On 10/13/2017 03:32 AM, Mohamed Chaouechi wrote:
Dear EPICS Tech-Talk,

We currently doing a research about EPICS, how to communicate with EPICS, EPICS topologies, and EPICS implementation in PLC IOC based systems.
As we are a group of students, and we are basically Electrical and Automation Engineers, the EPICS field is new for us, we have little knowledge about it.
We've tried to read through the website, still have few difficulties to go deeper in the content.
Our questions here are :
-How does 'EPICS' create a control system (the definition says so , "EPICS provides a number of tools for creating a control system"), meanwhile, another important part of another definition says "PS: When installing EPICS, does not create a control system"!
-Do we , as Automation Engineering students , need to learn the algorithm and the programming procedure if we will be maybe implementing EPICS with automated systems ? 
-EPICS is about collaboration between People, Labs, sites, is it mandatory or it can be used for educational individual use, if yes, what is the hardware needed for that.
-What are the software needed basically to use EPICS, as we will be using software like S7PLC or EtherCAT ? 

We appreciate having an answer soon as we are unfortunately under a time DDL.

Best Regards 











--
Mohamed Chaouechi 
Skype : elcaponeh 
Phone : +86 185 9140 8748
Wechat ID : Mohamedchaouechi


-- 
"Whether you think you can or think you can't, you're right" -- Henry Ford
_______________________________________________________________
Pierrick Hanlet
+44-79-48-86-01-97 (UK mobile)
+44-12-35-77-07-91 (UK home)
+1-630-888-0185 (US mobile)

Attachment: epics+HW2.png
Description: PNG image


References:
EPICS training information Mohamed Chaouechi

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