ZeroMQ subscriber to GNU Radio ZeroMQ source for digital OOK PWM signal.

ook_pwm_zeromq_subscriber.js

const zmq = require('zeromq')

const socket = zmq.socket('sub')

socket.connect('tcp://127.0.0.1:3000')
socket.subscribe('')

const shortSamples = 9
const longSamples = 34
const resetSamples = 348

let bit = 0
let code = 0
let codes = []
let samples = 0
let prevLevel = 0

socket.on('message', (buffer) => {
    for (let offset = 0; offset < buffer.length; offset += 4) {
        const currLevel = buffer.readFloatLE(offset)

        // logic level change detected
        if (prevLevel !== currLevel) {

            // logic level changed from high to low
            if (currLevel === 0 ) {
                if (samples >= longSamples) {
                    code = code | (1 << bit)
                    bit++
                } else {
                    if (samples >= shortSamples) bit++
                }
            } else {
                if (samples >= resetSamples) {
                    if (codes.push(code) >= 10) {
                        console.log(mode(codes))

                        codes = []
                    }

                    code = 0
                    bit = 0
                }
            }

            samples = 0
            prevLevel = currLevel
        }

        samples++
    }
})

function histogram(values) {
    let hist = {}

    values.forEach(value => {
        hist[value] = (hist[value] || 0) + 1
    })

    return hist
}

function mode(values) {
    let maxFreq = 0
    let modeValue
    
    for (const [value, freq] of Object.entries(histogram(values))) {
        if (freq > maxFreq) {
            maxFreq = freq
            modeValue = value
        }
    }

    return +modeValue
}