Modbus RTU and TCP
Reading meters, transmitters and VFDs, register maps, Float32 byte order and CRC.
03 · NET-01 · Industrial networks
Industrial networks: Modbus, RS485 and MQTT from sensor to server
Connecting field instruments, meters and controllers over Modbus RTU/TCP, RS485 and MQTT, with industrial wireless links and secure WireGuard tunnels between site and server.
Half of all monitoring failures are neither in the sensor nor in the software, but on the road between them: a wrong byte order, a duplicate address, a missing terminator, or a link that drops at night. I design the communication layer to work and keep working, from the RS485 pair inside the panel to an encrypted tunnel reaching the server.
What I do
RS485 network design
Daisy-chain wiring, termination and biasing, lengths and baud rates, and proper grounding.
MQTT and data transport
MQTT brokers, topic structure, and cutting data volume with edge deadband.
Secure remote access
WireGuard tunnels, separating OT from office IT, and Linux server administration.
Standards
Modbus RTU / TCPTIA/EIA-485MQTT 3.1.1 / 5HART
Technologies & skills
RS485ModbusMQTTWireGuardLinuxEthernetWireless sensor networks
Try it yourself
Projects from the field
UY-301
HS-IIoT platform: a 4th-generation industrial SCADA
An end-to-end, hardware-to-cloud system for critical industrial sites: power, generators and tanks on one screen.
SC-401Graduation project: telemetry & predictive maintenance
An engineering framework linking controllers over RS485 to automate fault detection and reduce downtime.
Terms
FAQ
What is the difference between Modbus RTU and Modbus TCP?
RTU runs on a serial line such as RS485 with binary frames and a CRC16 check; TCP runs on Ethernet and drops the CRC because TCP already checks the data. Function codes and register maps are the same in both.
Why does a Modbus float reading look wrong?
Usually word order: the value spans two registers and every vendor orders them differently (ABCD, CDAB and so on). Compare all four orders in the workshop’s Modbus toolkit.
What is the maximum RS485 cable length?
About 1200 m at low baud rates such as 9600 bps, less as the speed rises. Use shielded twisted pair and a 120 Ω terminator at the two ends of the line only.
Is MQTT a replacement for Modbus?
No, each has its place. Modbus reads devices on site; MQTT carries the data efficiently from site to server or cloud, and an edge gateway translates between them.
Have a project in this area?
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