WebSerialBarcodeScanner

This is an library that allows you to use barcode scanners in serial com port mode using WebSerial.

This library is part of @point-of-sale, a collection of libraries for interfacing browsers and Node with Point of Sale devices such as receipt printers, barcode scanners and customer facing displays.

What does this library do?

By default most barcode scanners emulate a keyboard meaning all numbers and letters of a barcode will be individually 'typed' by the barscanner. This means you either have to focus an input field before scanning, or you have to use global keyboard events and build some algorithm that can seperate out digits from barcodes from other digits that are being typed on the keyboard. This is error-prone and slow, but most barcode scanners can also be used in serial mode.

Depending on the model and manufacturer you might first need to scan a special configuration barcode to enable this mode. See the documentation of your barcode scanner for more information.

This library uses WebSerial to connect to the scanner and receive the barcodes in one event.

How to use it?

Load the webserial-barcode-scanner.umd.js file from the dist directory in the browser and instantiate a WebSerialBarcodeScanner object.

    <script src='webserial-barcode-scanner.umd.js'></script>

    <script>

        const barcodeScanner = new WebSerialBarcodeScanner();

    </script>

Or import the webserial-barcode-scanner.esm.js module:

import WebSerialBarcodeScanner from 'webserial-barcode-scanner.esm.js';

const barcodeScanner = new WebSerialBarcodeScanner();

Configuration

When you create the WebSerialBarcodeScanner object you can specify a number of options to help with the library with connecting to the device.

Serial port settings

Many devices that use serial ports can be configured to use different speeds and settings like databits, stopbits and parity and flow control. Sometimes these settings are hardcoded, sometimes they can be configured by DIP switches or other means. See the manual of your device for more information about how your device is configured and match the settings of your device with the properties below:

• baudRate Number that indicates the speed, defaults to 9600.
• bufferSize Size of the read and write buffers, defaults to 255.
• dataBits Number of data bits per frame, either 7 or 8, defaults to 8.
• flowControl: The flow control type, either none, or hardware, defaults to none.
• parity The parity mode, either none, even or odd. The default value is none.
• stopBits The number of stop bits at the end of the frame. Can be either 1 or 2 and defaults to 1.

For example, to set a baud rate of 9600:

const barcodeScanner = new WebSerialBarcodeScanner({ 
    baudRate: 9600
});

Symbology

Usually the barcode scanner does not transmit any information about the symbology of the barcode, just the value of the barcode itself.

However the library can make an educated guess based on the content. For example, if it starts with http it usually is a QR code. If it is 13 digits and the last digit is a check digit, it is usually an EAN13 code and similarly with 12 digits is usually a UPC-A.

By default this behaviour is turned off. If you want this library to guess the symbology you can turn it on:

const barcodeScanner = new WebSerialBarcodeScanner({
    guessSymbology: true
});

On some scanners it may actually be possible to add an AIM Code ID as a prefix to the barcode. This is a 3 character identifier for the symbology of the barcode. To enable this for your barcode scanner you may need to scan a configuration barcode. For more information look at the documentation of your barcode scanner. If this AIM Code ID is detected, it will be used to determine the symbology of the barcode.

By default this library will return barcodes of every symbology. However if you want to use this library in a specific environment, such as retail, you can limit this library to only allow symbologies that are used in retail, for example:

const barcodeScanner = new WebSerialBarcodeScanner({
    allowedSymbologies: [ 'ean13', 'ean8', 'upca', 'upce', 'qr-code' ]
});

This will allow all EAN and UPC barcodes. But also QR-codes because the retail industry is moving to the QR code based GS Digital Links in the coming years. These digital links contain an URL and can be used by consumers to read more about the product they are buying or have bought. But it also includes the Global Trade Identification Number (GTIN) that is also used by EAN and UPC barcodes.

If we find GS1 data such as the GTIN in the scanned barcode we will automatically decode it and place it in the data property:

barcodeScanner.addEventListener('barcode', e => {
    if (e.data?.gtin) {
        console.log(`Found barcode with GTIN ${e.data.gtin}`);
    }
});

Connect to a scanner

The first time you have to manually connect to the barcode scanner by calling the connect() function. This function must be called as the result of an user action, for example clicking a button. You cannot call this function on page load.

function handleConnectButtonClick() {
    barcodeScanner.connect();
}

Subsequent times you can simply call the reconnect() function. You have to provide an object with vendor id and product id of the previously connected barcode scanner in order to find the correct barcode scanner and connect to it again. If there is more than one device with the same vendor id and product id it won't be able to determine which of the two devices was previously used. So it will not reconnect. You can get the vendor id and product id by listening to the connected event and store it for later use. Unfortunately this is only available for USB connected devices. It is recommended to call this button on page load to prevent having to manually connect to a previously connected device.

barcodeScanner.reconnect(lastUsedDevice);

If there are no barcode scanners connected that have been previously connected, this function will do nothing.

However, this library will actively look for new devices being connected. So if you connect a previously connected barcode scanner, it will immediately become available.

To find out when a barcode scanner is connected you can listen for the connected event using the addEventListener() function.

barcodeScanner.addEventListener('connected', device => {
    console.log(`Connected to a device with vendorId: ${device.vendorId} and productId: ${device.productId}`);

    /* Store device for reconnecting */
    lastUsedDevice = device;
});

The callback of the connected event is passed an object with the following properties:

• type Type of the connection that is used, in this case it is always serial.
• vendorId In case of a USB barcode scanner, the USB vendor ID.
• productId In case of a USB barcode scanner, the USB product ID.

To find out when a barcode scanner is disconnected you can listen for the disconnected event using the addEventListener() function.

barcodeScanner.addEventListener('disconnected', () => {
    console.log(`Disconnected`);
});

You can force the scanner to disconnect by calling the disconnect() function:

barcodeScanner.disconnect();

Events

Once connected you can use listen for the following events to receive data from the barcode scanner.

Scanning barcodes

Whenever the libary detects a barcode, it will send out a barcode event that you can listen for.

barcodeScanner.addEventListener('barcode', e => {
    console.log(`Found barcode ${e.value}`);
});

The callback is passed an object with the following properties:

• value The value of the barcode as a string
• data If the barcode contains GS1 data, such as the Global Trade Identification Number (GTIN) the data will be parsed into elements.
• aim Optionally, the AIM Code ID, which is a 3 character ISO/IEC identifier and gives information about the symbology of the barcode which was scanned.
• symbology Optionally a library specific identifier of the symbology.
• guess If the symbology of this barcode is a guess, then true. If we are quite certain of the symbology, then false.
• bytes The raw bytes we've received from the scanner. This propery is an array containing one or more Uint8Array's.

Parsed GS1 data

The data property is optional, but if GS1 data is detected, it will contain an object with the following properties:

• gtin Optionally, if the GS1 elements define a GTIN, it will be listed here for quick reference.
• elements An array of all the GS1 elements that the barcode contains. Each element is an object with the folowing properties; ai: the appication identifier, label: a human readable label and value: the value of the element.

Symbologies

The symbology property can be any of the following common values for 1D barcodes:

ean8, ean13, upca, upce, code39, code93, code128, codabar, interleaved-2-of-5, gs1-databar-omni, gs1-databar-expanded

Or these 2D barcodes:

qr-code, data-matrix, aztec-code, pdf417

Example

A typical EAN 13 barcode would look like:

{
    value: "3046920029759",
    symbology: "ean13",
    guess: false,
    data: {
        gtin: "03046920029759",
        elements: [{
            ai: "01",
            label: "GTIN",
            value: "03046920029759"
        }]
    },
    bytes: [[
        0x30, 0x33, 0x30, 0x34, 0x36, 0x39, 0x32, 0x30, 
        0x30, 0x32, 0x1D, 0x37, 0x35, 0x39
    ]]
}

This library has been created by Niels Leenheer under the MIT license. Feel free to use it in your products. The development of this library is sponsored by Salonhub.