Balance Server

This turns a balance connected to the the computer into a WebSocket server that pushes readings.

Installing

Node.js

The latest Node.js (6.5.0 as of this writing) is required as this was written for ECMAScript 2015 (ES6). This can be obtained from the Node.js website.

You can determine the version of Node.js that is currently installed on your machine by typing the following into a terminal:

node --version

git

The current version of git as of this writing is 2.10.0. It can be obtained from the git website.

You can determine the version of git that is currently installed on your machine by typing the following into a terminal:

git --version

Installation "Gotcha"

Note: These instructions were written against OS X El Capitan version 10.11.16.

Note that if you download the git installer, and try to install it, that OS X may refuse to do so, saying that the .pkg file is from an unidentified developer.

If you get this message, you need to temporarily disable the portion of OS X security that controls this.

1. Go to System Preferences... under the Apple menu.
2. Choose Security and Privacy.
3. Locate the padlock at the bottom on the window, which says, Click the lock to make changes. and click on it.
4. Enter in the administrator password .
5. In the General tab, the lower half of the window has options with the description, Allow apps downloaded from:. Select Anywhere.
6. OS X will give a warning, Choosing 'Anywhere' makes you Mac less secure. Click on the button that says, Allow From Anywhere

Now OS X will allow you to install the latest version of git.

!!! Be sure to not leave the security setting as it is. !!! If you don't set the security setting back to where it was, your Mac is less secure. Do that similarly:

1. Go to System Preferences... under the Apple menu.
2. Choose Security and Privacy.
3. Locate the padlock at the bottom on the window, which says, Click the lock to make changes. and click on it.
4. Enter in the administrator password .
5. In the General tab, the lower half of the window has options with the description, Allow apps downloaded from:. Select Mac App Store and identified developers.

Installing the program

Open up a terminal window and type the following:

git clone https://github.com/starforgelabs/balance-server-2.git
cd balance-server-2
npm install

Options

--port=<port number> sets the port that the WebSocket server will listen on. Defaults to port 3333.

Running

A process monitor such as pm2 or forever is suggested.

sudo npm install -g pm2
pm2 start app.js

or

sudo npm install -g forever
forever start app.js

Debugging

Debugging information can ben enabled with the DEBUG environment variable. There are three sections that can be enabled independently:

• app - The main application, which includes the WebSocket server.
• proxy - The glue between a WebSocket connection and the serial port.
• balance - A wrapper for the serial port that pushes information with RxJS.

To enable everything,

export DEBUG="app proxy balance"
node app.js

WebSocket Commands

The commands sent to the WebSocket server are 'stringified" JSON.

The format of the JSON data can be found in the file api.d.ts.

List Detected Serial Devices

This will return a SerialListPacket, which is an array of SerialPortResponse objects. The important fields are:

• connected - A boolean that indicates whether the server is currently connected to this device.
• device - The name of the device, which is passed to the server in the connect command.
• prefer - This is true when the device is detected as an FTDI serial port. This suggests that the device is likely an Ohaus balance.

Example:

let ws = new WebSocket("ws://localhost:3333")
let command = { 
    command: "list"
}
ws.send(JSON.stringify(command))

Connect to Serial Device

This will tell the server to try connecting to the given serial device.

Example:

let ws = new WebSocket("ws://localhost:3333")
let command = { 
    command: "connect", 
    device: "/dev/cu-usbserial-000012FD" 
}
ws.send(JSON.stringify(command))

Disconnect from Serial Device

This will tell the server to disconnect from the current serial device.

Example:

let ws = new WebSocket("ws://localhost:3333")
let command = { 
    command: "disconnect"
}
ws.send(JSON.stringify(command))

Request Connection Status

This will tell the server to try connecting to the given serial device.

Example:

let ws = new WebSocket("ws://localhost:3333")
let command = { 
    command: "status" 
}
ws.send(JSON.stringify(command))

Simulate Balance Reading

This will tell the server to simulate receiving data from the balance.

Note: The server will append SIMULATED to the end of the received data attribute to be clear about the fact that this is not an actual balance reading.

Example:

let ws = new WebSocket("ws://localhost:3333")
let command = { 
    command: "simulate-data",
    data: "1.23 G ? NET"
}
ws.send(JSON.stringify(command))