async/await using serialport in node.js

问题

Working on the communication between PC and an Arduino-based Hardware with Node.js. This last device is implemented with G-Code, so if i send ‘G0’ I will receive two lines; one to confirm that the instruction has been received and a second one with data.

I would like to use async/await but something is wrong... here goes the code:

'use strict'
const SerialPort = require('serialport')
const Readline = SerialPort.parsers.Readline

const cardPort = new SerialPort('COM6', {
    baudRate: 115200,
    parity: 'none',
    stopBits: 1,
    dataBits: 8,
    flowControl: false,
    usePromises: true,
}, function(err) {
    if (err){
        console.log('error: ', err.message)
        port.close()
    } else {

    }
})

const cardParser = new Readline({ delimiter: '\r\n' })

cardPort.pipe(cardParser)

function checkCard(port, parser){
    port.write('G0\n', function () {
        console.log('message written')
        parser.on('data', (data) => { 
            console.log(data)
            return (data)
        })
    })
}

async function run () {
    const id = await checkCard(cardPort,cardParser)
    console.log(`ID response is: ${id}`)
}

run()

and this is the response I got:

ID response is: undefined
message written
Received: G0
ENCR1PT3R!

why ID response is not waiting until checkCard is executed?

Thanks in advance

回答1:

checkCard should return Promise to work, but looks like port.write is callback based. Enclose it in new Promise for it work.

function checkCard(port, parser){
    return new Promise(function(resolve, reject) { 
      port.write('G0\n', function () {
        console.log('message written')
        parser.on('data', (data) => { 
            console.log(data)
            resolve(data)
        })
      })
    });      
}

来源：https://stackoverflow.com/questions/50857586/async-await-using-serialport-in-node-js

标签

node.js

serial-port