serialport-synchronous

Overview

serialport-synchronous is a simple promise based library for Node.js that allows for synchronous request-response styled communication with serialport

Installation

npm install serialport-synchronous

Usage Scenario

In this example the serialport device has been configured to return a temperature value when it receives the command getTemp. We specify the expected response as a regular expression, and when the library receives that response the promise is resolved.

The serialport device also echos back the text: Received: getTemp, which we have no use for. This is ignored through the use of the bufferRegex property which is used to determine what should be buffered and returned in the promise resolver.

The errorRegex is used to determine if the response was deemed unsuccessful and the reject resolver should be invoked.

In this example, we assume the serialport device takes a while to initilise. When it is ready it will send the READY command. Through the use of the handlers property, we configure the main() function to run when we receive the READY command.

Success Scenario:

1. << READY
2. >> getTemp
3. << Received: getTemp
4. << Temp: 23.22

Error Scenario:

1. << READY
2. >> getTemp
3. << ERROR

Sample Code

import { SerialPortController } from '../src/index'

const TEMP_REGEX = /^Temp: (\d+\.\d+)$/
const ERROR_REGEX = /^ERROR$/
const READY_REGEX = /^READY$/

const controller = new SerialPortController({
  path: '/dev/ttyUSB0',
  baudRate: 19200,
  handlers: [{
    pattern: READY_REGEX,
    callback: main // call the main() function when READY_REGEX has matched.
  }]
})

// push the log events from the library to the console
controller.on('log', (log) => console[log.level.toLowerCase()](`${log.datetime.toISOString()} [${log.level.toUpperCase()}] ${log.message}`))

// open the serial port connection
controller.open()

async function main () {
  try {
    // send the getTemp text to the serialport
    const result = await controller.execute({
      description: 'Querying current temperature', // optional, used for logging purposes
      text: 'getTemp',                             // mandatory, the text to send
      successRegex: TEMP_REGEX,                    // mandatory, the regex required to resolve the promise
      bufferRegex: TEMP_REGEX,                     // optional, the regex match required to buffer the response
      errorRegex: ERROR_REGEX,                     // optional, the regex match required to reject the promise
      timeoutMs: 1000                              // mandatory, the maximum time to wait before rejecting the promise
    })
    
    // parse the response to extract the temp value
    const temp = result.match(TEMP_REGEX)[1]
    console.log(`\nThe temperature reading was ${temp}c`)
  } catch (error) {
    console.error('Error occured querying temperature')
    console.error(error)
  }
}

Output

2022-07-20T01:33:56.855Z [INFO] Connection to serial port '/dev/ttyUSB0' has been opened
2022-07-20T01:33:58.391Z [INFO] << READY
2022-07-20T01:33:58.392Z [INFO] Inbound message matched unsolicited handler pattern: /^READY$/. Calling custom handler function
2022-07-20T01:33:58.396Z [INFO] Querying current temperature
2022-07-20T01:33:58.397Z [INFO] >> [TEXT] getTemp
2022-07-20T01:33:58.415Z [INFO] << Received: getTemp
2022-07-20T01:33:58.423Z [INFO] << Temp: 16.89
2022-07-20T01:33:58.423Z [DEBUG] Received expected response, calling resolve handler

The temperature reading was 16.89c