In 2026, AUTONDMY’s OPENPLC V4 underwent a major update, with both the Editor and Runtime officially releasing V4! This series will conduct various tests using OPENPLC V4 in practice. Episode 3 introduces creating a Python FB.

Additionally, install the Open PLC Runtime on the Docker container of Advantech’s AMAX-7580 100D5A.

Let’s enjoy the FA!

Foreword

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Implementation

Now let’s actually start creating the program.

Editor Version

To use Python FB with OpenPLCV4, you must use version 4.1.2 or later.

Runtime Installation

Next, install Runtime directly to IPC using the following command.

git clone https://github.com/Autonomy-Logic/openplc-runtime.git cd openplc-runtime sudo ./install.sh

Please wait a moment…

Done!

Next, use the following command to check the runtime status of OPENPLC V4.

sudo systemctl status openplc-runtime.service

Trouble

Next, I’ll explain the error I encountered when installing Runtime directly on IPC and how I resolved it.

fatal: unable to access

The first error encountered was an inability to access github.com.

fatal: unable to access ‘https://github.com/Autonomy-Logic/openplc-runtime.git/’: Could not resolve host: github.com

Verify Internet Connection

First, check if you are connected to the Internet.

ping 8.8.8.8

DNS Resolution Verification

Next, we’ll verify if it can communicate with github.com.

ping github.com

DNS Settings Correction

In my case, it was a DNS configuration issue, so fixing it as shown below should work.

sudo nano /etc/resolv.conf nameserver 8.8.8.8 nameserver 8.8.4.4

Add Python FB

Next, add a Python function block. Click the + button in the project tree → Function Blocks → Set the Language to Python, then enter the POU name.

Done!So the Python FB template was generated.

Warning!

Using Python Function Blocks in OPENPLC V4 Runtime:

Python FB runs asynchronously from the PLC main runtime.
All variables are shared with the runtime via shared memory.
The block_init() function is called only once when the block starts.
The block_loop() function is called periodically (approximately every 100ms).
This periodic call does not follow the PLC scan cycle.
There is no guarantee that block_loop() will execute once per scan.
Use this block for tasks without time constraints.
For logic that must align with the PLC scan cycle, use standard IEC 61131-3 function blocks.

Code

Here is the Python FB code for this session.

This program creates a text file and continuously increments a variable within a block_loop.

from multiprocessing import shared_memory
import struct
import time
import os

def block_init():
print(‘Block was initialized’)
global iCounter,xCreate
iCounter=0
xCreate=0

def block_loop():

print(‘Block has run the loop function’)
global iCounter
global xCreate
iCounter=iCounter+1
if xCreate:
with open(“/home/oem/Documents/example.txt”, “w”) as f:
f.write(“Hello, World!”)

xCreate=False