Parsers

Pick a parser

If your protocol…	Use
ends each message with a newline	ReadlineParser
uses any other byte sequence as a separator	DelimiterParser
has fixed-size messages	ByteLengthParser
splits on a regex (mixed line endings, e.g. \r?\n)	RegexParser
length-prefixes each packet	PacketLengthParser
relies on inter-byte silence (Modbus RTU)	InterByteTimeoutParser
prints a banner before it's ready	ReadyParser
frames binary with SLIP escapes	SlipEncoder/Decoder
brackets data with start/end markers	StartEndParser
is ccTalk (coin/bill validators)	CCTalkParser
is CCSDS Space Packet	SpacePacketParser

---

ReadlineParser

Emits one string per line. The line-oriented sweet spot for most Arduino-class boards.

import { SerialPilot, ReadlineParser } from 'serialpilot'
const port = new SerialPilot({ path: ‘/dev/ttyUSB0’, baudRate: 9600 })
const parser = port.pipe(new ReadlineParser({ delimiter: ‘\r\n’ }))
parser.on(‘data’, line => console.log(line))

Option	Type	Default	Notes
delimiter	string | Buffer	'\n'	Line terminator.
encoding	string	'utf8'	Text encoding for emitted strings.
includeDelimiter	boolean	false	Whether emitted lines keep the delimiter.

---

DelimiterParser

Generic version of ReadlineParser — split on any byte sequence and emit Buffers (or strings if you set encoding downstream).

const parser = port.pipe(new DelimiterParser({
delimiter: Buffer.from([0xAA, 0x55]),
}))

Option	Type	Notes
delimiter	string | Buffer | number[]	Required. Length ≥ 1.
includeDelimiter	boolean	Default false.

---

ByteLengthParser

Emits a Buffer every time a fixed number of bytes have been received.

const parser = port.pipe(new ByteLengthParser({ length: 8 }))
parser.on('data', buf => console.log(buf)) // 8 bytes each time

Throws if length is missing, zero, or negative.

---

RegexParser

Like ReadlineParser, but the splitter is a RegExp. Useful when devices send mixed line endings:

const parser = port.pipe(new RegexParser({ regex: /\r?\n/ }))

Option	Type	Default
regex	RegExp	required
encoding	string	'utf8'

---

PacketLengthParser

For protocols that prefix each packet with its length. Reads the length field at a configured offset and waits for the full packet to land before emitting.

const parser = port.pipe(new PacketLengthParser({
delimiter: 0xa5,        // header byte
packetOverhead: 5,      // non-payload bytes
lengthBytes: 1,         // size of the length field
lengthOffset: 2,        // offset of the length field
maxLen: 0xff,
}))

Option	Default	Notes
delimiter	0xaa	Header byte that starts a packet.
packetOverhead	2	Bytes outside the payload.
lengthBytes	1	Size of the length field.
lengthOffset	1	Position of the length field.
maxLen	0xff	Largest valid packet — guards against runaway frames.

---

InterByteTimeoutParser

Emits buffered data when the line stays quiet for interval milliseconds. Modbus RTU's classic "3.5-character silence" framing fits here.

const parser = port.pipe(new InterByteTimeoutParser({ interval: 30 }))

Option	Default	Notes
interval	required	Milliseconds of silence (≥ 1).
maxBufferSize	65536	Bytes buffered before forced emit.

---

ReadyParser

Buffers everything until a configured ready sequence arrives, then emits ready and forwards bytes from that point on. Most Arduino-class boards print a banner on reset; this parser tells you when they're done.

const parser = port.pipe(new ReadyParser({ delimiter: 'READY' }))
parser.on('ready', () => port.write('PING\n'))
parser.on('data', console.log) // data after the banner

---

SlipEncoder / SlipDecoder

Two complementary streams that implement RFC 1055 SLIP framing. Common in ESP-IDF tools and embedded MCUs.

const decoder = port.pipe(new SlipDecoder())
decoder.on('data', frame => console.log('frame:', frame))
const encoder = new SlipEncoder()
encoder.pipe(port)
encoder.write(Buffer.from([0x01, 0x02, 0xc0])) // 0xc0 escaped automatically

Both honour the standard SLIP byte values: END=0xC0, ESC=0xDB, ESC_END=0xDC, ESC_ESC=0xDD.

---

StartEndParser

Emits the bytes between a configured start delimiter and a configured end delimiter. Suits NMEA, custom binary frames, or anything that uses opening/closing markers.

const parser = port.pipe(new StartEndParser({
startDelimiter: Buffer.from([0xa5]),
endDelimiter: Buffer.from([0x5a]),
}))

---

CCTalkParser

Parses the ccTalk protocol used by coin acceptors and bill validators in vending and gaming hardware. Emits each fully-received frame as a Buffer.

const parser = port.pipe(new CCTalkParser())
parser.on('data', frame => console.log(frame))

---

SpacePacketParser

Parses CCSDS Space Packet framing — the international standard used by spacecraft telemetry/telecommand links. Emits objects with parsed primary header fields and the payload buffer.

const parser = port.pipe(new SpacePacketParser())
parser.on('data', packet => {
console.log(packet.header.apid, packet.data)
})

Header fields exposed: version, type, secondaryHeaderFlag, apid, sequenceFlags, sequenceCount, length.

---

Writing your own

A parser is just a Node Transform stream. Roll your own by extending stream.Transform and implementing _transform(chunk, _, cb) — most of the parsers above are under 100 lines of source.