About the timeout error in `system.serial.readLine`

Ignition
,
1

Hello
I have a question about system.serial.readLine.

I'm new to Ignition. Currently, I'm using system.serial to connect to a serial communication device.
Connection tests confirmed the device connection and data retrieval worked, but when I try to retrieve data after a timeout with system.serial.readLine, it throws an error.

Even when I create if statements or Try / catch blocks to handle cases where the value is NULL, the error still occurs.
How should I handle this situation? Should I change the settings on the device side?

data = system.serial.readLine("COM3", 20000)
2

I would post the config and the errors you get, we aren't mind readers.

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3

Understood, that's correct! My apologies.
The script I created is as follows.
The error details are contained within the JSON file.
This file was generated when the error occurred.

■code：

try:
        #Definition of Connected Devices
        system.serial.configureSerialPort(port="COM3",
        bitRate=system.serial.BIT_RATE_9600,
        dataBits=system.serial.DATA_BITS_8,
        handshake=system.serial.HANDSHAKE_NONE,
        hardwareFlowControl=False,
        parity=system.serial.PARITY_NONE,
        stopBits=system.serial.STOP_BITS_1)
        
        #Connection
        system.serial.openSerialPort("COM3")
        
        #Data acquisition
        data = system.serial.readLine("COM3", 50000)
        
        if data is None:
           data = "Timeout occurred"
        
        system.serial.closeSerialPort("COM3")

        return data
     #The returned data is being used by each component.

■Error Details：

NonResponsiveEdt-2025-08-29_193604 (1).json (65.4 KB)

4

The problem is that you are running this script directly in the foreground UI thread, which is not allowed to wait. You need to use system.util.invokeAsynchronous() to launch a background thread to do all of the serial line work. The background thread would report results by writing to client tags or using a shared jython variable, as background threads are not permitted to directly access windows and components.

1 Like
5

Thank you! I'll try running a connection test using that method!

6

You should study this old topic if you wish to manipulate your UI from the background:

1 Like