Modbus Communication Issue via RS-485 (TRB145): Randomly Missing One Out of 15 Measurements

[Erlandas]

Hello,

I’m using a Teltonika TRB145 device, connected to electricity meters via RS-485, using the Modbus Serial Client functionality.

Issue Description:

Communication generally works correctly, however, at certain time intervals, one of the requests is failed. (randomly lost). The issue repeats unpredictably —each time a different request is missing.

• Configured: 15 separate Modbus requests
• Frequency: 60
• Timeout: 1 second
• Status: All devices show “Up”, but Failed Requests still occur intermittently.
• Devices are connected in a Daisy Chain via RS-485.

Steps Already Taken:

Tried changing baud rate (4800, 9600, 19200).
→ Notably, the number of failed requests varied by baud rate, with the least packet loss observed at 9600.

• Verified wiring and termination resistors.
• All meters are configured with identical Modbus RTU parameters.
• Using standard RS-485 cable (PROFIBUS 2Y(st)CY 1x2x0.64).
• Configured Modbus polling period to 30 seconds, and Data to Server sending period to 60 seconds, to allow enough time for data collection before transmission.

Can you support in identifying the possible causes or solutions.
Is this a known issue?
Screen with drops:

Meter configuration :

Meters request info:

Data to server settings:

Thank you for your assistance!

[Martynas]

Hello,

Apologies for the delay. Could you please confirm whether this issue still persists with the latest 7.13.4 firmware installed on the device?

If the issue still occurs, for testing purposes I’d recommend trying the following adjustments:

• Set both Modbus data requesting and Data to Server sending periods back to their default 60 second values;
• Increase the Modbus device timeout to 5 seconds;
• Set number of timeouts to 1.

Then monitor if this improves the communication stability. If no noticeable improvement is observed, we’ll need to take a deeper look into this matter and continue troubleshooting privately.

Best regards,