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Industrial Communication Modules
How do a PLC, a drive, a meter, a gateway and the cloud actually talk to each other?
Every machine needs a way to move data: between a PLC and its I/O, between a PLC and a drive, from a meter to a screen, or from a remote pump to the cloud. This page puts fifteen common options on one sheet, grouped into five families: industrial Ethernet, fieldbus, serial, wireless and IoT/edge. Open a family to see the protocol, a typical module, where it is used, its good and bad points and its key numbers. Then use the finder to shortlist the right one for your job.
Speeds and distances are typical values for the standard. Your cable, device and network layout will set the real limit. Always check the module datasheet and your controller's supported protocols before you buy.
Compatibility usually decides first: your PLC, drive or meter only speaks certain protocols. The other five questions choose among the rest.
Both axes are logarithmic. Joined dots show the same bus at two settings: fast and short, or slow and long. Wireless dots show nominal link rate and typical range, not guaranteed throughput.
A real machine uses several at once. The PLC talks to drives and I/O over a real-time Ethernet bus, to small sensors over IO-Link, and to old meters through a serial gateway. A Raspberry Pi or edge box reads the PLC over Modbus TCP or OPC UA and sends data to the cloud with MQTT, through the plant network or a 4G/5G router. Keep control traffic and cloud traffic on separate networks.
RS485 is not Modbus
RS485 is the electrical layer: two wires, differential signalling. Modbus RTU is a message format that often runs on it. Other protocols, such as PROFIBUS DP, also use RS485 wiring.
Same cable, different protocol
PROFINET, EtherCAT and EtherNet/IP all use standard-looking Ethernet cable and RJ45 or M12 plugs. They do not talk to each other. A device must support the protocol your controller uses.
Ethernet switch rules differ
An ordinary office switch is fine for EtherNet/IP and Modbus TCP, and PROFINET RT. EtherCAT devices are chained, not switched. PROFINET IRT needs special switches built into the devices.
Wi-Fi is not hard real-time
Radio traffic can be delayed by interference. Use Wi-Fi for HMIs, mobile machines and monitoring, not for safety or fast motion loops. Safety over wireless needs certified safety protocols.
Raspberry Pi has no cellular modem
A Pi 5 has Gigabit Ethernet, dual-band Wi-Fi and Bluetooth. For 4G/5G add a USB modem or an industrial router. For fieldbuses add a HAT or a gateway.
Gateways translate, they do not speed up
A protocol gateway (for example Modbus RTU to EtherNet/IP) joins two networks. It cannot make the slow side faster, and it adds a little delay. Plan polling time for the slowest device.
Module names are examples of real products in each family, not recommendations. Cost is shown only as a relative scale, because prices vary by brand and seller. Distances, speeds and cycle times are typical values for the standards, and the real figures depend on cable, device and layout.