wiegand-encoder

Lightweight module that encodes and decodes 26, 34, or 38 bit Wiegand protocol credentials for communication with access control systems.

Installation

npm install wiegand-encoder

Usage

// Modules
import wiegand from 'wiegand-encoder';

// CommonJS
const wiegand = require('wiegand-encoder');

Encoding

The encode() function converts a card number and facility code into binary, counts the bit parity of each half of the message, and wraps it in parity bits.

const encoded = wiegand.encode(cardNumber, facilityCode);

wiegand.encode(wiegand.encode(324, 90));
// 00101101000000001010001000

If the specified card number or facility code are too high for the standard bit length, it will throw an exception. The largest possible card number in 26-bit protocol is 65535, and the largest possible facility code is 255.

Decoding

The decode() function validates the parity bits on either side of the message, then parses the message content from binary back into integers.

const { cardNumber, facilityCode } = wiegand.decode('00101101000000001010001000');
// { cardNumber: 324, facilityCode: 90 }

If the parity bits are invalid, decode() will throw an exception.

To check parity on a message without decoding it, use parity.validate().

try {
  wiegand.parity.validate('00101101000000001010001000');
} catch (error) {
  console.error(error);
}

Alternate bit length

By default, encode() encodes all messages as 26-bit.

To encode a larger message (e.g. 34-bit, 38-bit, etc.) send the bit length for the card number and facility code to the encode() function.

26-bit credentials use a card number length of 16 and a facility code length of 8. To encode a 34-bit message, use a card number length of 22 and a facility code length fo 10.

wiegand.encode(cardNumber, facilityCode, cardNumberLength, facilityCodeLength);

wiegand.encode(wiegand.encode(324, 90, 22, 10));
// 0000101101000000000000001010001000

The decode() function also supports optional cardNumberLength and facilityCodeLength parameters, but will attempt to infer them based on the content of the length of the message if omitted.

const { cardNumber, facilityCode } = wiegand.decode('0000101101000000000000001010001000');
// { cardNumber: 324, facilityCode: 90 }

License

MIT © Jesse Youngblood