mtbc-reader - Provides extensive support for interfacing with Mettler Toledo BC scales.

• mtbc-reader - Provides extensive support for interfacing with Mettler Toledo BC scales.
  • Installation
  • Examples
  • Usage
    • Reference the scale reader
    • Getting the weight from the scale
  • Getting the scale's status
    • Tell whether or not the scale is plugged in
    • Raw status
  • Complete API
    • .getWeightLb()
    • .getWeightKg()
    • .getWeightOz()
    • .events
    • .isPluggedIn()
    • .isFault()
    • .isMoving()
    • .isUnderZero()
    • .isOverweight()
    • .getStatus()
    • .pause()
    • .resume()
    • .getByte()

Installation

npm install mtbc-reader

const scale = require("mtbc-reader");

Currently tested for OS: Windows 10, Ubuntu 18 (with libusb)

Currently tested for hardware: MT PS60 scales

Examples

A basic example application is provided in the src/ directory.

Usage

Reference the scale reader

const scale = require('mtbc-reader')

Manual registration of the scale is never required, the library handles all scale/usb registration, connect, and disconnect events - you only need to reference the library to use it.

Getting the weight from the scale

There are two methods of obtaining the weight from the scale.

The simplest method is .getWeightLb()

var weight = scale.getWeightLb();
console.log("Weight on scale is: "+weight+" pounds.")

Additionally, .getWeightKg() and .getWeightOz() can be used as well.

The second method is via the events system.

scale.events.on("change", function(weight) {
    //weight = scale.getWeightKg(); or manual conversion if you need something other than pounds
    console.log("The weight on the scale has changed! The weight is: "+weight+" pounds.")
});

The event is better suited for live visual interfaces or any other situation where you might consider polling the first method.

The event stream can be paused with scale.pause() and resumed with scale.resume()

• Note: if the scale is unplugged or otherwise unregistered the event will simply stop firing, it will not disconnect or throw any errors - .isPluggedIn() can be used to check status if required.
• Note: The event only returns in pounds, you can either call .getWeightKg(), .getWeightOz() in the event callback, or manually convert to another unit.

Getting the scale's status

A number of helper functions are included in the library to obtain more information about the scale.

Tell whether or not the scale is plugged in

scale.isPluggedIn() Can be used to determine whether the scale is plugged in or not.

if (scale.isPluggedIn()) {
  console.log("Scale is plugged in!");
} else {
  console.log("Error: Scale is not plugged in!");
}

Further helper functions are listed in the full API below.

Raw status

Additionally, you can just get the raw scale status and process it yourself:

var status = scale.getStatus();

switch(status) {
    ...
}

The status format is as follows:

• 1: Fault,

• 2: Stable @ 0,

• 3: In motion,

• 4: Stable,

• 5: Under 0,

• 6: Over-weight,

• 7: Requires calibration,

• 8: Requires re-zeroing

• Note: 0 will be returned by the reader if getStatus() is accessed while the scale is unplugged or otherwise unregistered

Complete API

.getWeightLb()

• Returns the scale weight in pounds, to the hundredth decimal point.
• Note: If the scale is unplugged, any attempts to get the weight will return 0.

.getWeightKg()

• Returns the scale weight in kilograms, to the hundredth decimal point.
• Note: If the scale is unplugged, any attempts to get the weight will return 0.

.getWeightOz()

• Returns the scale weight in ounces, to the hundredth deceimal point.
• Note: If the scale is unplugged, any attempts to get the weight will return 0.

.events

• EventEmitter for weight change, use event "change".

.isPluggedIn()

• Returns true if the scale is plugged in.

.isFault()

• Returns true if the scale is warning that a fault has/is occurring

.isMoving()

• Returns true if the scale is encountering a load greater than it's official max capacity.

.isUnderZero()

• Returns true if the scale is returning a value below zero (either negative numbers or simply refusing to display anything on the LCD)
• Note: If the scale is below zero, any attempts to get the weight value will round up to 0.

.isOverweight()

• Returns true if the scale is encountering a load greater than it's official max capacity.

.getStatus()

• Obtain the raw status of the scale in IDs 1-8 Status format is as follows:

1: Fault,
2: Stable @ 0,
3: In motion,
4: Stable,
5: Under 0,
6: Over-weight,
7: Requires calibration,
8: Requires re-zeroing

.pause()

• Pause sending of the weight change events.

.resume()

• Resume sending of the weight change events.

.getByte()

• Returns the raw data byte from the scale. Byte format for scale is as follows:

Byte 0: Report ID
Byte 1: Scale status 
Byte 2: Weight unit 
Byte 3: Data scaling
Byte 4: Scale Weight LSB
Byte 5: Scale weight MSB