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APM supports serial communication with electronic scales for weight-based transactions. This guide shows you how to configure and test scale connections.

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Adding a New Scale

1

Navigate to Scales

From the main menu, select Scales to open the scale management page.Click the + Add Scale button to create a new scale configuration.
2

Configure Basic Information

ID (Id)
A unique identifier for the scale.
Example: bascula01, scale_checkout
The ID cannot be changed after creation.
Name (Name)
A friendly display name for the scale.
Example: Báscula Principal, Checkout Scale 1
3

Select COM Port

Port Name (PortName)
Select the COM port where the scale is connected.Example: COM1, COM3, COM5
Click the ⟳ refresh button to reload available COM ports if your scale isn’t listed.
If you don’t see your COM port:
  • Check Device Manager in Windows to verify the port number
  • Ensure scale drivers are installed
  • Verify the USB-to-Serial adapter is properly connected
4

Configure Serial Communication

Set the serial communication parameters to match your scale’s specifications.Baud Rate (BaudRate)
Data transmission speed in bits per second.
Default: 9600
Common values: 1200, 2400, 4800, 9600, 19200, 38400Data Bits (DataBits)
Number of data bits per transmission.
Default: 8
Common values: 7, 8Parity (Parity)
Error checking method:
  • None - No parity checking (most common)
  • Odd - Odd parity
  • Even - Even parity
  • Mark - Mark parity
  • Space - Space parity
Default: NoneStop Bits (StopBits)
Number of stop bits:
  • None - No stop bits
  • One - 1 stop bit (most common)
  • Two - 2 stop bits
  • OnePointFive - 1.5 stop bits
Default: One
5

Save and Activate

The Active toggle (IsActive) determines if the scale is enabled.Default: true (enabled)Click Save Scale to save your configuration.

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Finding Your Scale’s Serial Settings

Serial communication parameters vary by manufacturer and model. Check:
  1. Scale manual - Most manufacturers document these settings
  2. Scale display menu - Some scales allow viewing/changing settings via on-screen menu
  3. Manufacturer website - Download the technical specifications or user manual

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Common Scale Configurations

Baud Rate: 9600
Data Bits: 8
Parity: None
Stop Bits: One

Baud Rate: 9600
Data Bits: 7
Parity: Even
Stop Bits: One

Baud Rate: 9600
Data Bits: 8
Parity: None
Stop Bits: One

Baud Rate: 9600
Data Bits: 8
Parity: None
Stop Bits: One

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Configuration Example

{
  "Id": "bascula01",
  "Name": "Báscula Principal",
  "PortName": "COM3",
  "BaudRate": 9600,
  "DataBits": 8,
  "Parity": "None",
  "StopBits": "One",
  "IsActive": true
}

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Enum Values

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ScaleParity

ValueIntegerDescription
None0No parity checking
Odd1Odd parity
Even2Even parity
Mark3Mark parity
Space4Space parity

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ScaleStopBits

ValueIntegerDescription
None0No stop bits
One11 stop bit
Two22 stop bits
OnePointFive31.5 stop bits

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Troubleshooting

  • Verify the COM port is correct in Device Manager
  • Check that no other application is using the same COM port
  • Ensure the scale is powered on and in ready state
  • Try different baud rate settings if unsure of scale configuration
  • Verify all serial parameters match your scale’s specifications
  • Check for loose cable connections
  • Ensure the scale is calibrated properly
  • Test with the scale’s built-in diagnostics if available
  • Install or update the scale’s USB driver
  • Check Device Manager for any hardware errors (yellow exclamation mark)
  • Try a different USB port
  • Click the ⟳ refresh button after connecting the scale
  • Check for electromagnetic interference near the scale
  • Use a shielded serial cable
  • Avoid running the cable near power lines or motors
  • Try lowering the baud rate (e.g., from 9600 to 4800)

Template Editor

Use scale data in receipt templates

API Reference

Scale configuration API endpoints

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