Installing the CODESYS Bridge

The PLC Assist Bridge is a Python script that runs inside CODESYS, enabling real-time communication between your local CODESYS project and PLC Assist. Once running, PLC Assist can read your project tree, edit code, compile, and deploy -- all from the browser.

Requirements

PLC Environment

System

You also need a PLC Assist account.

Step 1: Download the Bridge Scripts

You'll need two scripts: one to start the bridge and one to stop it.

This downloads two files:

• plc-assist-bridge-start.py -- starts the bridge
• plc-assist-bridge-stop.py -- stops the bridge

Step 2: Copy to CODESYS Scripts Folder

Copy both .py files to the CODESYS scripting directory. The location depends on your CODESYS version:

Standard (per-user):

C:\Users\<YourUsername>\AppData\Local\CODESYS\ScriptDir\

Standard (system-wide):

C:\Program Files\CODESYS 3.5.xx.xx\CODESYS\ScriptDir\

Step 3: Add Toolbar Shortcuts (Recommended)

Instead of navigating menus every time, add the bridge scripts as toolbar buttons for one-click access:

1. In CODESYS, go to Tools > Customize
2. Select the Toolbars tab
3. Click New to create a toolbar (e.g. "PLC Assist")
4. Switch to the Commands tab
5. In the Categories list, select ScriptEngine Commands
6. Find plc-assist-bridge-start and plc-assist-bridge-stop in the commands list
7. Drag them onto your new toolbar

You now have dedicated Start/Stop buttons in your CODESYS toolbar. No more digging through menus.

Step 4: Start the Bridge

With a CODESYS project open:

Option A -- Toolbar button (recommended): Click the plc-assist-bridge-start button in your toolbar.

Option B -- Menu: Go to Tools > Scripting > Execute Script File, then select plc-assist-bridge-start.py.

When the bridge starts successfully, the CODESYS window title will show [Bridge Active].

Step 5: Connect from PLC Assist

1. Open PLC Assist in your browser
2. Click Connect
3. PLC Assist will automatically detect the bridge on localhost:8555

Stopping the Bridge

Option A -- Toolbar button: Click the plc-assist-bridge-stop button.

Option B -- From PLC Assist: Click the Connected button in PLC Assist and select Stop Bridge.

Option C -- Menu: Go to Tools > Scripting > Execute Script File, then select plc-assist-bridge-stop.py.

Updating the Bridge

When a new version is available:

1. Download the new scripts from PLC Assist
2. Replace the existing files in your ScriptDir folder
3. Restart the bridge

The toolbar shortcuts will automatically use the updated scripts.

Troubleshooting

Scripts Not Appearing in ScriptEngine Commands

• Verify both .py files are in the correct ScriptDir folder
• Check that the file extension is .py (not .py.txt)
• Restart CODESYS after adding the files

Bridge Won't Start

• Make sure a CODESYS project is open before starting the bridge
• Check the CODESYS message log for error details
• Ensure no other application is using port 8555

PLC Assist Can't Connect

• Verify the CODESYS window title shows [Bridge Active]
• Check that your firewall allows connections on localhost:8555
• Try stopping and restarting the bridge

Bridge Disconnects During Use

If PLC Assist shows "Disconnected", the bridge may have stopped. Restart it using the toolbar button or menu, then click Connect again in PLC Assist.

For more help, see the troubleshooting guide.