digimatic-js

TypeScript/browser library for communicating with Mitutoyo Digimatic SPC measuring instruments via the Web Serial API.

Browser compatibility: Chrome and Edge desktop (≥ 89). Not supported on Firefox, Safari, or mobile.

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Installation

Generally speaking, to bundle this library in your project, you can use:

# Replace "pnpm" with your package manager or runtime of choice (npm, yarn, bun, deno, etc.)
pnpm install jsr:@lgtm/digimatic-js

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Quick start

Single device

import { DigimaticDevice } from '@lgtm/digimatic-js'

const device = new DigimaticDevice()

device.on('reading', (r) => {
  console.log(`Reading: ${r.value} ${r.unit}`)  // e.g. "Reading: 25.340 mm"
})

device.on('stateChange', (state) => {
  console.log('State:', state) // 'connecting' | 'connected' | 'disconnected' | 'error'
})

device.on('error', (err) => {
  console.error('Error:', err.message)
})

// Opens the native port selection dialog (requires a user gesture)
await device.connect()

// Press DATA on the device to receive a reading

Promise for a single reading

await device.connect()

// Waits for the next reading (with configurable timeout)
const reading = await device.nextReading()
console.log(reading.value, reading.unit)

Multiple devices with DigimaticManager

import { DigimaticManager } from '@lgtm/digimatic-js'

const manager = new DigimaticManager()

// Each addDevice() opens a port selection dialog
const id1 = await manager.addDevice()
const id2 = await manager.addDevice()

// Global callback for all readings
const unsubscribe = manager.onReading((deviceId, reading) => {
  console.log(`[${deviceId}] ${reading.value} ${reading.unit}`)
})

// Remove a device
await manager.removeDevice(id1)

// Unregister the callback
unsubscribe()

// Disconnect everything
await manager.disconnectAll()

Mitutoyo DMX-8/2 multiplexer

The DigimaticDmx8 class communicates with the DMX-8/2, a microcontrolled interface that connects up to 8 Digimatic instruments to a single RS-232C port.

Continuous mode

import { DigimaticDmx8 } from '@lgtm/digimatic-js'

const dmx = new DigimaticDmx8()

dmx.on('reading', (r) => {
  console.log(`CH${r.channel}: ${r.value} ${r.unit}`)
})

dmx.on('error', (err) => console.error(err.message))

// Opens the native port selection dialog (requires a user gesture)
await dmx.connect()

// Start continuous transmission from all channels
await dmx.startContinuous()

// Stop when done
await dmx.stopContinuous()
await dmx.disconnect()

Poll a single channel

await dmx.connect()

// Send "C1" and wait for the response
const reading = await dmx.readChannel(1)
console.log(reading.channel, reading.value, reading.unit)

Manual packet parsing (advanced)

import { parsePacket, PacketAccumulator } from '@lgtm/digimatic-js'

// Direct parsing of a raw packet (13 bytes)
const raw = new Uint8Array([0x00, 0x02, 0x05, 0x03, 0x04, 0x00, 0x00, 0x02, 0x00, ...])
const reading = parsePacket(raw)

// Accumulator for fragmented streams
const acc = new PacketAccumulator()
const packets = acc.push(incomingBytes)
packets.forEach(p => console.log(parsePacket(p)))

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API

DigimaticDevice

Constructor

new DigimaticDevice(options?: DigimaticDeviceOptions)

Option	Type	Default	Description
port.baudRate	number	9600	Serial baud rate
port.dataBits	7 | 8	7	Data bits
port.stopBits	1 | 2	1	Stop bits
port.parity	string	'even'	Parity
port.flowControl	string	'none'	Flow control
bufferSize	number	1000	Max readings in history buffer
readTimeout	number	5000	Timeout for nextReading() in ms

Methods

Method	Description
connect(port?)	Connects (opens dialog if port is omitted)
disconnect()	Disconnects and releases the port
nextReading()	Promise → next reading
clearHistory()	Clears the history buffer
on(event, cb)	Adds a listener
off(event, cb)	Removes a listener
once(event, cb)	One-time listener

Properties

Property	Type	Description
state	DigimaticConnectionState	Current state
isConnected	boolean	True if connected
history	ReadonlyArray<DigimaticReading>	Readings buffer
lastReading	DigimaticReading | null	Last received reading

Events

Event	Payload	Description
reading	DigimaticReading	New reading received
stateChange	DigimaticConnectionState	Connection state changed
error	Error	Communication error

DigimaticDmx8

Methods

Method	Description
connect(port?)	Connects (opens dialog if port is omitted)
disconnect()	Disconnects and releases the port
startContinuous()	Sends GS — device streams all channels continuously
stopContinuous()	Sends GR — stops continuous transmission
readChannel(n)	Sends Cn (1–8), returns a Promise → single reading
on(event, cb)	Adds a listener
off(event, cb)	Removes a listener
once(event, cb)	One-time listener

Events

Event	Payload	Description
reading	DigimaticDmx8Reading	New reading received
stateChange	DigimaticConnectionState	Connection state changed
error	Error	Communication error

DigimaticDmx8Reading

interface DigimaticDmx8Reading {
  channel: number      // Channel index (1–8)
  value: number        // Numeric value (e.g. 11.378)
  unit: 'mm' | 'in'   // Unit of measure
  timestamp: number    // Reception time as ms epoch
}

DigimaticReading

interface DigimaticReading {
  value: number        // Numeric value (e.g. 25.340)
  unit: 'mm' | 'in'   // Unit of measure
  timestamp: number    // Reception time as ms epoch
  raw: Uint8Array      // Raw packet (13 bytes) for debugging
}

DigimaticError

class DigimaticError extends Error {
  code: 'UNSUPPORTED' | 'PORT_BUSY' | 'PARSE_ERROR' | 'CONNECTION_LOST' | 'TIMEOUT' | 'DEVICE_ERROR' | 'UNKNOWN'
}

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Hardware setup

The Digimatic SPC protocol uses a proprietary 5-pin connector (Mitutoyo Mini-DIN). To connect it to a PC:

1. Mitutoyo USB-ITN cable (264-016): official SPC → USB adapter, appears as a Virtual COM Port
2. SPC → RS-232 cable + generic RS-232 → USB adapter
3. Arduino/microcontroller as a bridge (for DIY projects)

Once connected, the device appears as a serial port in the navigator.serial.requestPort() dialog.

DMX-8/2 multiplexer

The Mitutoyo DMX-8/2 connects up to 8 Digimatic instruments to a single RS-232C port (D-SUB 9). Use it when you need to read multiple gauges simultaneously from one serial connection.

• Connect the DMX-8/2 to the PC via a DB9 RS-232 → USB adapter
• Connect up to 8 Digimatic instruments to the DMX-8/2 inputs
• The device appears as a single serial port — use DigimaticDmx8 to communicate with it

Serial parameters used by the DMX-8/2: 9600 baud, 8 data bits, 1 stop bit, no parity, no flow control.

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Publishing

This package is published on JSR.

pnpx jsr publish

Local development

pnpm install
pnpm dev # serve demo at http://localhost:5713

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License

MIT