@keiser/echip-webusb

Keiser Air eChip WebUSB Library

Project

This library handles communication with the EChip USB reader using WebUSB.

Required Hardware: USB to 1-Wire/iButton Adapter (DS9490)

Required Drivers: 1-Wire/iButton Drivers for Windows

Installation

Install with NPM: npm install @keiser/echip-webusb

Usage

Import singleton instance from module using preferred module loading technique.

import EChipReaderWatcher from '@keiser/echip-webusb'

if (EChipReaderWatcher.isConnected) {
  console.log('EChip Reader Connected 😄')
}

The EChipReaderWatcher handles permissions and USB connection events. On first load, the browser will not have provided a grant to the site to access the USB device, so the EChipReaderWatcher.start() method must be called by an event that originates from a user action. This may only be required once on the first visit to the site, or it may be required each time the site is loaded based on browser vendors preferred implementation.

connectButton.addEventListener('click', async () => {
  try {
    await EChipReaderWatcher.start()
  } catch (error) {
    console.error(error.message)
  }
})

Once the EChipReaderWatcher.start() method has been called the class will prompt the browser for permission and begin watching for devices matching the EChip Readers device signature. To be alerted when a device is found, pass a function to the EChipReaderWatcher.onConnect() method.

EChipReaderWatcher.onConnect((echipReader) => {
  console.log('EChip Reader Connected 😄')
})

The EChipReaderWatcher.onConnect() will pass in an EChipReader object which is the object bound to the physical device connected. This library is capable of handling multiple EChip Reader devices simultaneously, so the onConnect() method has potential for returning multiple EChipReader devices over the course of the application's life.

echipReader.onDisconnect(() => {
  console.log('EChip Reader Disconnected 😞')
})

The EChipReader object has a onDisconnect() method which will alert when the EChip Reader has been disconnected for some reason. Once an EChipReader object has been disconnected, it is disposed and cannot be used again. The next time the device is connected, a new EChipReader object will be returned.

echipReader.onEChipDetect(async (echip) => {
  console.log('EChip Connected: ' + echip.id)
  console.log(await echip.getData())
})

The EChipReader object also has an onEChipDetect() method which will alert when a valid EChip has been placed into the reader. The event passes in an EChip object that can be used to interact with the EChip data directly. Just like the EChipReaderWatcher.onConnect() method, the EChipReader.onEChipDetect() method can be called multiple times for multiple EChips all being handled concurrently. Once an EChip is disconnected, the EChip object is disposed and cannot be reused.

Full example usage:

import EChipReaderWatcher from '@keiser/echip-webusb'

document.addEventListener('DOMContentLoaded', event => {
  const connectButton = document.querySelector('#connect') as HTMLInputElement

  if (connectButton) {
    connectButton.addEventListener('click', async () => {
      try {
        await EChipReaderWatcher.start()
      } catch (error) {
        console.error(error.message)
      }
    })
  }

  EChipReaderWatcher.onConnect((echipReader) => {
    console.log('EChip Reader Connected 😄')

    echipReader.onEChipDetect(async (echip) => {
      console.log('EChip Connected: ' + echip.id)
      console.log(await echip.getData())
    })

    echipReader.onDisconnect(() => {
      console.log('EChip Reader Disconnected 😞')
    })
  })
})

API

EChipReaderWatcher

The EChipReaderWatcher is a singleton class which handles the USB device monitoring and permissions handling. There can be only one EChipReaderWatcher instance created within a window scope, so the library instantiates the class during import and preserves a single instance for all imports.

Properties

Name	Type	Usage
isConnected	Boolean	Indicates whether an eChip Reader Device is connected

Properties

Name	Parameters	Return Type	Usage
onConnect	Listener<EChipReader>	Disposable	Adds an event listener for when an eChip Reader Device is connected

import EChipReaderWatcher from '@keiser/echip-webusb'

document.addEventListener('DOMContentLoaded', event => {
  const connectButton = document.querySelector('#connect') as HTMLInputElement

  if (connectButton) {
    connectButton.addEventListener('click', async () => {
      try {
        await EChipReaderWatcher.start()
      } catch (error) {
        console.error(error.message)
      }
    })
  }

  EChipReaderWatcher.onConnect((echipReader) => {
    console.log('EChip Reader Connected 😄')

    echipReader.onEChipDetect(async (echip) => {
      console.log('EChip Connected: ' + echip.id)
      console.log(await echip.getData())
    })

    echipReader.onDisconnect(() => {
      console.log('EChip Reader Disconnected 😞')
    })
  })
})

References

Maxim Integrated 1-Wire USB Android notes

Maxim Integrated 1-Wire USB Android project

Copyright and License

Copyright Keiser Corporation under the MIT license.