A Transform stream for protocols that prefix each packet with its length. Reads the length field at a configured offset and emits a complete packet once that many bytes have been received.

npm install @serialpilot/parser-packet-length

Usage

const { SerialPilot, PacketLengthParser } = require('serialpilot')

const port = new SerialPilot({ path: '/dev/ttyUSB0', baudRate: 9600 })
const parser = port.pipe(new PacketLengthParser({
  delimiter: 0xa5,        // packet header byte
  packetOverhead: 5,      // bytes outside the payload
  lengthBytes: 1,         // size of the length field
  lengthOffset: 2,        // byte offset of the length field
  maxLen: 0xff,           // largest valid packet
}))
parser.on('data', console.log)

API

new PacketLengthParser(options)

| Option | Type | Default | Description | | ---------------- | ------ | ------- | ------------------------------------------ | | delimiter | number | 0xaa | Header byte that begins each packet. | | packetOverhead | number | 2 | Non-payload bytes per packet. | | lengthBytes | number | 1 | Size of the length field in bytes. | | lengthOffset | number | 1 | Byte offset of the length field. | | maxLen | number | 0xff | Maximum allowed packet length. |

See the SerialPilot README for the full set of parsers.