Modbus RTU FAQ

Unable to Read Tag Value, Error Code 3002

Enable DEBUG logging, check the log, inspect the data flow, and verify if the device has responded with data. If there is a response, check if the data is correct (serial devices may produce exceptions when multiple upstream masters collect data).
Check if the station number is correct.
Verify if the address is correct (Modbus address for Neuron starts from 1).
Some devices may not support reading a single point at a time, so all points need to be configured (Neuron automatically optimizes batch reading).
Serial wiring issues.
Incorrect serial port configuration.
The device supports Modbus TCP protocol instead of Modbus RTU. Try using the Modbus TCP plugin.

Tag Value Invalid, Error Code 3008

The device is offline, and data cannot be updated.
The device does not respond with data within a certain period.
The device supports Modbus TCP protocol instead of Modbus RTU. Try using the Modbus TCP plugin.

Tag Value Read does not Match Expectations

Incorrect data type.
Incorrect byte order.
Presence of multiple upstream masters collecting data results in data corruption.
The DTU has enabled registration or heartbeat packets, causing Neuron to consider data flow data as incorrect.
The device actively uploads data, but the standard Modbus only supports requesting and then responding with corresponding data.
The device supports Modbus TCP protocol instead of Modbus RTU. Try using the Modbus TCP plugin.