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

Here is the module for the SDS011, according to the manual to check the checksum and get proper value for PM2.5 and PM10.

const o = {};

function checkvalidity(bufferHex) {

    let  sum = 0;
    for (let i = 2; i < 8; i++) {
        sum = sum + parseInt(bufferHex[i], 16);
    }

    sum = sum &0xFF;
    const validCheckSum = parseInt(bufferHex[8],16);

    return sum == validCheckSum;
}

o.init = function (serial, callback) {
    console.log("> mod-dustsensor - init");

    //--- Exemple buffer
    //  data <Buffer aa  c0  1b  05  7d  08  9c  eb  2c  ab>
    //               170 192 27  5   125 8   156 235 44  171

    let bufferDecimal = [];
    let bufferHex = [];
    let bufferLength = 0;

    serial.on('data', function (data) {

        for (index in data) {
            let charDecimal = data.charCodeAt(index); // chope la valeur decimal du caractère
            let charHex = data.charCodeAt(index).toString(16); // chope la valeur Hex du caractère

            bufferDecimal.push(charDecimal);
            bufferHex.push(charHex);
            bufferLength++;

            if (+charDecimal == 171 && bufferLength == 10) {

                let validity = checkvalidity(bufferHex);

                if(validity){
                    // PM2.5 value -  ((PM2.5 High byte[3] *256) + PM2.5 low byte[2] ) / 10
                    // PM10 value -  ((PM10 High byte[5] *256) + PM10 low byte[4] ) / 10
                    let pm2_5 = ((bufferDecimal[3] * 256 ) + bufferDecimal[2])/10;
                    let pm10 = ((bufferDecimal[5] * 256 ) + bufferDecimal[4])/10;
                    callback({
                        pm2_5:pm2_5,
                        pm10:pm10
                    });
                }

                 bufferLength = 0;
                 bufferDecimal=[];
                 bufferHex=[];

            }
        }
    });
};

module.exports = o;

Entry point :

const modDustSensor = require('mod-sds011');

function onInit() {

    Serial1.setup(9600, {rx: B7, tx: B6});

    modDustSensor.init(Serial1, function(pmValues){
        console.log(`PM-2.5: ${pmValues.pm2_5} --- PM-10: ${pmValues.pm10} `);
    });

}