epics-tca

TypeScript Realization of EPICS Channel Access Client Liberary

• TypeScript Realization of EPICS Channel Access Client Liberary
  • About
  • Install
  • Usage of Channel Access
    • Get
    • Put
    • Monitor
  • Usage of PV Access
  • Performance

About

This is the TypeScript version EPICS Channale Acceess (CA) client library. It provides a TypeScript/JavaScript interface for an EPICS CA client communicating with CA servers.

This library complies the CA protocol specifications.

Install

In your TypeScript/JavaScript project, run

npm install epics-tca

Usage of Channel Access

Get

Create a .ts file (e.g. simpleGet.ts) with following contents:

import { Context } from "epics-tca";
async function simpleGet(name: string) {
    let channel = await context.createChannel(name);
    return await channel?.get();
}

let context = new Context();
context.initialize().then(() => {
    simpleGet("FE:Scope_1:RMS2").then((data: any) => {
        console.log("FE:Scope_1:RMS2", data.data);
        context.destroyHard();
    });
});

Run the transpiled simpleGet.js file, you will get the following result:

$ node simpleGet.js 
FE:Scope_1:RMS2 [ 2.2934632737106067 ]

Put

Create a .ts file (e.g. simplePut.ts) with following contents:

import { Context } from "epics-tca";
async function simplePut(name: string, value: number) {
    let channel = await context.createChannel(name);
    const value0 = await channel?.get();
    console.log("Before:", name, value0?.data);
    await channel?.put([value]);
    return await channel?.get();
}

let context = new Context();
context.initialize().then(() => {
    simplePut("val1", 9527).then((data: any) => {
        console.log("After: ", "val1", data.data);
        context.terminate();
    });
});

Run the transpiled simplePut.js file, you will get the following result:

$ node simplePut.js 
Before: val1 [ 2 ]
After:  val1 [ 9527 ]

Monitor

Create a .ts file (e.g. simpleMonitor.ts) with following contents:

import { Context } from "epics-tca";

async function tcaMonitor(name: string) {
    let channel = await context.createChannel(name);
    let monitor = await channel?.createMonitor(monitorListener);
    await monitor?.subscribe();
}
function monitorListener(monitor: ChannelMonitor) {
    console.log(monitor.name, ":", monitor.data.data);
}

let context = new Context();
context.initialize().then(() => {
    tcaMonitor("FE:Scope_1:RMS2");
});
setTimeout(() => {
    console.log("Terminate program");
    context.terminate();
}, 5 * 1000)

Run the transpiled simpleMonitor.js file, you will get the following result:

$ node simpleMonitor.js
FE:Scope_1:RMS2 : [ 2.296598922566252 ]
FE:Scope_1:RMS2 : [ 2.2929398313489786 ]
FE:Scope_1:RMS2 : [ 2.299754072515923 ]
FE:Scope_1:RMS2 : [ 2.298171626156998 ]
Terminate program

Usage of PV Access

Performance

Benefited from the asynchronous and event driven design of Node.js, the EPICS TCA can create EPICS channels efficiently. Below is the time used to create a batch of channels:

Number of PVs	Time [seconds]
1000	0.104
2000	0.184
5000	0.334
10000	0.603
15000	0.728
20000	0.923
25000	1.318
30000	1.553
35000	2.032
40000	2.432
45000	2.748
50000	3.082
60000	3.727
80000	5.583
100000	9.095

Each channel updates once every second. During the test, after the channels are created, the test program monitors the updates. For 100000 channels, the memory usage is about 450 MB when they are monitored, and the CPU usage is about 50% on a 2.3 GHz Intel Core i9-9880H processor with MacOS 12.4.