Error when sending second start command to Cylon.js to blink LED

Question

Using Node.js, express and cylon.js, I'm getting a post request and blinking an LED using a raspberry Pi. I receive the first post request fine, the code runs and the LED blinks. However on the second post request I receive an error:

events.js:146
      throw err;
      ^

Error: Uncaught, unspecified "error" event. (Error occurred while writing value 1 to pin 23)
    at DigitalPin.emit (events.js:144:17)
    at DigitalPin.<anonymous> (/home/pi/tech-corner/devTracker/node_modules/cylon/lib/io/digital-pin.js:70:12)
    at fs.js:1134:21
    at FSReqWrap.oncomplete (fs.js:82:15)

Note that in the code below I'm using pin: 16. So I'm confused as to why it's trying to write to pin 23.

var express = require('express')
var bodyParser = require('body-parser')
var app = express()
var Cylon = require('cylon')

var pi = Cylon.robot({
  connections: {
    raspi: { adaptor: 'raspi' }
  },

  devices: {
    led: { driver: 'led', pin: 16 }
  },

  work: function (my) {
    after((1).second(), function () {
      console.log('Post request recieved! Toggle the LED')
      my.led.toggle()
    })

    after((2).second(), function () {
      my.led.toggle()
    })

    after((5).seconds(), function () {
      console.log('I\'m shutting down now.')
      pi.halt()
    })
  }
})

app.set('port', process.env.PORT || 1337 - 1)

// parse application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: false }))

// parse application/json
app.use(bodyParser.json())

app.post('/', function (req, res) {
  console.log(req.body.user_name)

  pi.start()

  res.end('Hello')
})

app.listen(app.get('port'), function () {
  console.log('Node app is running at http://localhost:' + app.get('port'))
})

Any help greatly appreciated. I assume my raspberryPi set-up is fine since it works on the first hook.

EDIT: Incase anyone comes across this and has a similar problem. I decided to go with pigpio which was a lot easier.

Answer 1

I heard of Cylon for the first time here by your Question. So you can estimate the quality of my answer. ;-)

It could be that, after the call of the .halt() method the system will be reinitialized and is not ready to start again without reconfiguration as you try in the POST request. The following Code might work if I'm right ;-).

var express = require('express')
var bodyParser = require('body-parser')
var app = express()
var Cylon = require('cylon')

var piCnf = {
  connections: {
    raspi: { adaptor: 'raspi' }
  },

  devices: {
    led: { driver: 'led', pin: 16 }
  },

  work: function (my) {
    after((1).second(), function () {
      console.log('Post request recieved! Toggle the LED')
      my.led.toggle()
    })

    after((2).second(), function () {
      my.led.toggle()
    })

    after((5).seconds(), function () {
      console.log('I\'m shutting down now.')
      my.halt()
    })
  }
};

app.set('port', process.env.PORT || 1337 - 1)

// parse application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: false }))

// parse application/json
app.use(bodyParser.json())

app.post('/', function (req, res) {
  console.log(req.body.user_name)

  var pi = Cylon.robot(piCnf);
  pi.start()

  res.end('Hello')
})

app.listen(app.get('port'), function () {
  console.log('Node app is running at http://localhost:' + app.get('port'))
})

I have read some examples now (it's an interesting framework) and a few documentation pages and as far as I can see Cylon is a standalone system with its own connection adapters for rest calls (APIs) and so on. So I see no need for using express in parallel.

But it is easy to use Cylon without express in a similar fashion like this. I've modified the code of an example from the original Cylon page. (https://cylonjs.com/documentation/guides/working-with-robots/)

var flagBlinkOn = false;

Cylon.robot({
  name: "testbot",
  connections: {
    "loopback": { adaptor: "loopback" }
  },


  devices: {
   led: { driver: 'led', pin: 16 }
  },

  work: function() {
     every((1).seconds(), function() {
      my.led.toggle()
     });
  },

  switchOn: function(my) {
    flagBlinkOn = true;
  },

  switchOff: function(my) {
    flagBlinkOn = false;
  }
});

// GET /api/robots/testbot/commands
// => ['switchOff', 'switchOn']
// GET /api/robots/testbot/switchOff 
// -> switch off blinking
// GET /api/robots/testbot/switchOn
// -> switch on blinking

Of cause: this configures a GET request and I do not know if POST is possible. I'm also not sure how to change the ip adress and the port. But there is a configuration object and surely some more connection types and devices. And sorry, I did not tested this Code.

Perhaps there is someone who could give you a complete answer. But until then I'll hope I could help you a little bit.