External module requirement
An RS485/Modbus connection requires a suitable external communication module. Verify electrical levels, power, isolation needs, and interface compatibility with NetRelay before the project begins.
Physical layer
Apply A/B polarity, common reference, shielding, and cable topology according to equipment documentation. RS485 generally uses a bus topology; star branches may cause communication problems. Determine termination and bias requirements for the line ends and connected devices.
Serial communication settings
Baud rate, data bits, parity, stop bits, and slave address must match. Obtain register addresses and data types from the current manufacturer map, and test differences in zero/one-based addressing and byte/word order.
Phased commissioning
Start with one device and a short line for read tests. Test writes only against a safe register or in maintenance mode. Log timeouts, CRC errors, and offline behavior, and use bounded retries in control software.