labjack-switch.js

console.log('Hello LabJack')

var ljn = require('labjack-nodejs');
var NanoTimer = require('nanotimer')
var fs = require('fs')
var now = require('performance-now')
var path = require('path')
var mkdirp = require('mkdirp').mkdirp

var createDeviceObject = ljn.getDevice();
var device = new createDeviceObject();
device.openSync();
console.log('Board ready')


var timer = new NanoTimer()

var interval = process.argv[2]
var repeats = process.argv[3]
var samples = process.argv[4]

mkdirp('./logs')
var filename = path.basename(process.argv[1], '.js')
var ws = fs.createWriteStream('./logs/' + filename + '-' + interval + '-' + repeats +'.log' )

var iteration = 0

obj = {
  'board': true,
  'date': new Date(),
  'time': now().toFixed(3)
}
console.log(JSON.stringify(obj))

var curTime = 0
var prevTime = 0
var value = 0

timer.setInterval(function() {
  curTime = now()
  for (i=0; i<repeats; i++) {
    value = device.readSync('FIO0')
  }
  for (i=0; i<repeats; i++) {
    device.writeSync('FIO1', value)
  }
 
  obj = {
    'sw': value,
    'it': iteration,
    'ts': curTime.toFixed(3),
    'df': (curTime - prevTime).toFixed(3)
   }
  prevTime = curTime
  iteration++
  if (iteration > samples) {
    device.closeSync();
    timer.clearInterval()
  }
  //console.log(JSON.stringify(obj))
  ws.write(JSON.stringify(obj) + '\n')
}, '', interval)


process.on('SIGINT', function() {
    device.closeSync();
    timer.clearInterval()
});

$ node switch.js 1m 1 50000

Run switch test with labjack connected to my laptop (make sure power on!!) and test with oscilloscope

Reliably see < 1.5 ms delays

Also try just a single read/write call, but still have 1 ms to 2 ms latencies

 value = device.rwManySync(['FIO0', 'FIO1'], [0, 1], [1, 1], [null, value[0]])

Also see 1 ms to 2 ms latencies for analog switch

 value = device.rwManySync(['AIN0', 'DAC0'], [0, 1], [1, 1], [null, value])[0]

Overall seems like board can run reliably in the 500 Hz - 1 kHz regime