[SOLVED]Need help interpreting the serial output of a sensor

@Robin

Here my small Node script, I've just connect de SDS011 to an USB to my computer (port COM8):

///////////////////////////////////
// Hello, SDS011
///////////////////////////////////
const SDS011Wrapper = require("sds011-wrapper");

const sensor = new SDS011Wrapper("COM8"); // Use your system path of SDS011 sensor.

console.log("process.env " , process.env);

sensor
    .setReportingMode('active')
    .then(() => {
        console.log("Sensor is now working in active mode.");
        return sensor.setWorkingPeriod(0); // Sensor will send data as soon as new data is available.
    })
    .then(() => {
        console.log("Working period set to 0 minutes.");
        console.log("\nSensor readings:");

        // Since working period was set to 0 and mode was set to active, this event will be emitted as soon as new data is received.
        sensor.on('measure', (data) => {
            console.log(`[${new Date().toISOString()}] ${JSON.stringify(data)}`);
        });
    });

I've added a console.log to know what the serialPort npm Node module serial output is like (I've edited the file wrapper.js in the node module directory : node_modules\sds011-wrapper\wrapper.js)

Here a sample view of wrapper.js where I've put my console.log:

const SerialPort = require('serialport');
const EventEmitter = require('events');

const SensorState = require("./core/sensor-state.js");
const SensorCommand = require("./core/sensor-command.js");

const addChecksumToCommandArray = require("./core/packet-utils.js").addChecksumToCommandArray;
const verifyPacket = require("./core/packet-utils.js").verifyPacket;

const PacketHandlers = require("./core/packet-handlers.js");

const ALLOWED_RETRIES = 10; // Number of retries allowed for single command request. 
const COMMAND_RETRY_INTERVAL = 150; // Time between sequential retries.

class SDS011Wrapper extends EventEmitter {

    /**
     * Open sensor.
     *
     * @param {string} portPath - Serial port path
     */
    constructor(portPath) {
        super();

        this._port = new SerialPort(portPath, { baudRate: 9600 });
        this._state = new SensorState();

        this._commandQueue = [];
        this._isCurrentlyProcessing = false;
        this._retryCount = 0;

        this._port.on('error', function (err) {
            console.log('Error: ', err.message);
        });

        this._port.on('close', () => {
            console.log('SDS011Wrapper port closed');
            this.close();
        });

        /**
          * Listen for incoming data and react: change internal state so queued commands know that they were completed or emit data.
          */
        this._port.on('data', (data) => {
            console.log("///// data ////// " , data);
            if (verifyPacket(data)) {
            ...
            ...

now the output :

///// data //////  <Buffer aa c0 f3 1b 1f 4e 9c eb 02 ab>
[2019-06-22T16:29:46.134Z] {"PM2.5":715.5,"PM10":1999.9}

you can see that the BaudRate is default to 9600 (wrapper.js), and I've set the same value when I use the sensor connected to Espruino Pico, here is my code :

function onInit() {
  
        Serial1.setup(9600, {rx: B7, tx: B6});
        Serial1.on('data', function (data) {
             console.log("> data  : " , data);
        }
}

with result like :

> data  :  ­
> data  :  ¶
> data  :  
> data  :  «
> data  :  =
> data  :  ¼
> data  :  Œ
> data  :  ¶
> data  :  
> data  :  ¯
> data  :  ¾
> data  :  ä
> data  :  q
> data  :  =
> data  :  }
> data  :  þ
> data  :  ú
> data  :  N
> data  :  œ
> data  :  ë
> data  :  Ï
> data  :  ÿ
> data  :  
> data  :  
> data  :  N
> data  :  Ü
> data  :  ÿ
> data  :  ü
> data  :  ¡
> data  :  
> data  :  
> data  :  Î
> data  :  œ
> data  :  ÿ