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<== Date ==> | <== Thread ==> |
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Subject: | Re: EPICS training information |
From: | Pierrick Hanlet <[email protected]> |
To: | Mohamed Chaouechi <[email protected]>, "[email protected]" <[email protected]> |
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:
-- "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) |
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