A Weintek MT8106iP running an EasyBuilder Pro V6.10.02.284 project could ping an Arduino Opta WiFi PLC (AFX00006), but it could not read the PLC’s mapped variables through Modbus TCP/IP. The confirmed cause was the PLC runtime state, not either device’s IP address.
Recognize the Failure Pattern
Both devices had valid addresses on the same network, and ping succeeded. This confirmed basic IP reachability but did not confirm that the PLC was making mapped variables available to the HMI. The remaining symptom was that the MT8106iP received no register data.
| Check | Observed result | Engineering conclusion |
|---|---|---|
| HMI and PLC addressing | Valid addresses on the same network | No addressing fault was identified |
| Ping | Successful | Basic network connectivity existed |
| HMI register read | No mapped data received | Check PLC runtime state before changing network settings |
Correct the PLC Runtime State
The Arduino Opta was in STOP mode after the controller project was downloaded. In that state, the MT8106iP could not access or read the mapped tag variables over the network. Place the Opta in RUN mode so the downloaded application executes before testing HMI communication.
Verify Modbus TCP Communication
- Confirm that the MT8106iP and AFX00006 still have valid IP addresses on the same network.
- Confirm ping connectivity between the devices.
- Check the Opta runtime state after every project download. If it is stopped, place it in RUN mode.
- From the HMI, read a mapped PLC variable and confirm that its displayed value follows the controller value.
- After reads succeed, test any required writes and confirm the mapped PLC variable changes.
If ping succeeds but mapped data remains unavailable, capture the HMI device settings, both device IP addresses, the PLC runtime state, and the affected variable mapping. These observations separate network reachability from application-runtime and mapping problems.
FAQ
Why can my MT8106iP ping an Arduino Opta but not read Modbus registers?
Ping verifies basic IP connectivity only. In the reported configuration, the Opta was in STOP mode, which prevented the HMI from reading mapped variables.
What should I check after downloading a project to an Arduino Opta?
Check the controller runtime state. If the Opta is in STOP mode, place it in RUN mode before testing mapped-variable access from the HMI.
Which software and hardware versions were involved in this issue?
The configuration used a Weintek MT8106iP, EasyBuilder Pro V6.10.02.284, and an Arduino Opta WiFi PLC model AFX00006.