Modbus RTU / TCP
Read mapped PLC registers over RS-485 or Ethernet. This gives structured values without duplicating every field signal.
Open the NORVI X Modbus guide
PLC
data collection hub
Connect Your Existing PLC to Cloud and Data Collection
Keep the PLC that already runs the machine. Add NORVI X beside it to collect PLC and field data through Modbus RTU/TCP, digital inputs, 0-10 V or 4-20 mA interfaces, then publish selected data over Ethernet, Wi-Fi or optional 4G.
Modbus RTU
Modbus TCP
24 V Digital I/O
0-10 V
4-20 mA
MQTT / HTTPS
Designed for retrofit monitoring, PLC data acquisition, cloud telemetry and gradual IIoT upgrades without forcing a controls migration.
Existing PLC
Machine logic stays in place
NORVI X
Acquire, buffer, process and publish
SCADA / Cloud
MQTT, HTTPS, dashboards and APIs
Modbus registers
Machine states
Analog process values
RS-485 + EthernetBuilt into every NORVI X CPU
200 I/OMaximum modular I/O scale
Up to 5 kHzFast digital input on X-DI4
4G OptionalX2 and X3 for cellular deployments
Integration strategy
Start with the least invasive data path
For an installed PLC, the best retrofit usually leaves the proven control program alone. Choose the method that exposes the data you need with the smallest electrical and software change.
Parallel Digital Status
Observe run, stop, alarm, contactor, limit and pulse states through protected digital inputs when the same signal can be shared safely.
Review X-DI4 fast inputAnalog Signal Acquisition
Acquire 0-10 V and 4-20 mA process signals using the correct wiring method, input impedance and loop-voltage budget.
View 4-20 mA input moduleListen-Only Modbus Capture
Observe existing Modbus RTU traffic without becoming the bus master. Configure NORVI X to receive only, then validate serial settings, termination and bus loading during commissioning.
See the Modbus data pathDirect Sensor Inputs
Where sharing PLC signals is undesirable, add dedicated sensors or transducers to NORVI X and keep the measurement path independent.
Choose expansion modules
Quick decision table
Which PLC data collection method fits?
Use this table during the first site survey. The method can be mixed, for example Modbus for process values and parallel digital inputs for a few high-speed states.
| Method | Best for | PLC program change | NORVI X hardware | Engineering note |
|---|---|---|---|---|
| Modbus RTU | Registers, counters, alarms, setpoints | None to low | Built-in RS-485 | Preferred if the PLC can expose a stable register map. |
| Modbus TCP | Ethernet PLCs and plant LANs | None to low | Built-in Ethernet | Use network segmentation and read-only access where practical. |
| 24 V digital parallel input | Run, fault, contact, pulse state | Usually none | X-DI4 / X-DI8 / X-DI16 | Confirm PNP/NPN logic, common reference and input loading. |
| 0-10 V signal sharing | Speed, pressure, level and analog position | Usually none | X-AV4 | Often possible in parallel if the source can drive the combined input impedance. |
| 4-20 mA loop sharing | Process transmitters | Electrical review | X-AI4 | Do not simply parallel two current inputs. Use a valid series loop or signal splitter/isolator. |
| Passive RTU observation | Existing master/slave traffic | Usually none | Built-in RS-485 | Configure NORVI X as a receive-only observer so it does not transmit onto the existing bus. |
Parallel wiring
Share signals only when the electrical behavior is known
Parallel PLC monitoring can be a clean retrofit because it avoids changing the control code. It is not one universal wiring method. Digital, voltage and current-loop signals behave differently, so the acquisition circuit must be selected and verified for each signal type.
- Digital inputs: confirm 24 V level, PNP/NPN behavior, common reference and combined loading.
- Fast pulses: X-DI4 supports direct GPIO acquisition and documented fast-input operation up to 5 kHz.
- 0-10 V: parallel measurement can be practical when the signal source can drive both input impedances without unacceptable error.
- 4-20 mA: current inputs are generally not placed in parallel. Use a series arrangement only when the loop compliance budget allows it, or use a proper isolator/splitter.
Digital status sharing
A field state can feed the existing PLC and a NORVI X digital input when the source and both input circuits are electrically compatible.
24 V Sensor / ContactMachine state
JunctionValidated common
PLC DI + NORVI X DITwo monitored inputs
0-10 V measurement
Voltage inputs can often observe the same source in parallel. Check source drive capability and the effective parallel input impedance before commissioning.
0-10 V TransmitterVoltage source
Signal SplitHigh-impedance inputs
PLC AI + X-AV4Parallel voltage read
4-20 mA current loop
Do not copy the 0-10 V parallel-wiring pattern. Use a validated series loop or an active signal splitter/isolator, and verify the transmitter has enough compliance voltage for every burden in the loop.
4-20 mA TransmitterCurrent loop
PLC AIExisting measurement
X-AI4 / IsolatorValidated loop path
Modbus integration
Use PLC registers before duplicating field wiring
Every NORVI X CPU includes RS-485 and Ethernet. Where the PLC already exposes Modbus, reading a documented register map is usually the cleanest path to PLC data acquisition.
Modbus RTU master polling
NORVI X can poll a PLC or other Modbus slave over RS-485, decode holding/input registers and move selected values into local logging or cloud telemetry.
Modbus TCP
For Ethernet-connected PLCs, use IP networking and Modbus TCP where available. This avoids adding another RS-485 node and is easier to scale across a plant LAN.
Listen-only RTU capture
NORVI X can observe existing Modbus RTU exchanges in receive-only mode. Match the bus serial settings and commission the connection so the observer does not transmit or disturb the existing network.
PLC to cloud
Turn PLC data into a controlled telemetry pipeline
Collect only the tags that create operational value, buffer locally when needed, and publish through the network that fits the site. NORVI X supports Ethernet, Wi-Fi and optional cellular hardware, with MQTT/MQTTS and HTTP/HTTPS available in the software stack.
PLC / Field DataRegisters, digital states and analog values
NORVI X EdgeFilter, scale, timestamp and apply local logic
Local BufferMicroSD supports local logging and store-forward buffering when
connectivity is interrupted
SCADA / CloudMQTT broker, HTTPS API, dashboards or historian
Engineering considerations
Commission the retrofit without disturbing the control system.
Keep the existing PLC in control, validate shared signals electrically, and verify the data path under real operating conditions before deployment.
Validate shared electrical signalsCheck grounds, common references, input loading, isolation and
4-20 mA loop burden before commissioning.
Keep PLC control logic authoritativeUse NORVI X for data acquisition and connectivity without
unnecessarily changing established machine-control behavior.
Commission listen-only Modbus carefullyMatch baud rate, framing and bus topology, then verify that
receive-only observation does not disturb existing RTU
traffic.
Test store-forward recoveryVerify local buffering, retained timestamps and upload recovery
through an intentional network interruption before
deployment.
Complement or replace
Keep the PLC when it is doing the job. Replace it only when the application allows.
This hub is primarily for brownfield data collection. NORVI X can also act as the main controller in suitable new or redesigned systems, but replacement should be an engineering decision rather than a marketing default.
Use NORVI X beside the PLC
Best for retrofits where the installed PLC remains responsible for machine control.
- Cloud telemetry and dashboards
- Production counters and machine-state logging
- Energy, pressure, flow or condition monitoring
- Adding cellular connectivity without touching the plant LAN
Consider NORVI X as the controller
Best for applications where open programming, modular I/O and integrated connectivity fit the control requirements.
- New OEM machines and panels
- Non-safety automation and remote control
- Flexible data acquisition plus local control
- Projects standardized on Arduino, ESP-IDF or MicroPython
Technical resources
Continue from architecture to implementation
Use the exact NORVI X documentation for wiring, expansion selection and firmware setup before commissioning an installation.
ProductNORVI X Modular ControllerCPU variants, expansion modules, connectivity and technical
specifications.
GuideNORVI X Getting StartedCPU selection, expansion architecture, network setup and
programming environments.
GuideModbus RTU Master and SlaveRS-485 wiring, register model, setup and production
considerations.
ReferenceOn-Board I/O and CommunicationsBuilt-in Ethernet, RS-485 and CPU-level hardware details.
SelectorChoosing Expansion ModulesPlan compatible digital, analog and communication expansion
combinations.
ToolNORVI X Configuration ToolBuild a CPU and expansion stack and check documented compatibility
rules.
Often yes. If the PLC already exposes usable Modbus registers, NORVI X can read those values without changing the control logic. Parallel digital or analog acquisition may also avoid PLC program changes, but the electrical interface must be validated.
It can be possible when the signal type, voltage, PNP/NPN behavior, common reference and combined input loading are compatible. Treat it as an electrical design check rather than a universal wiring rule.
Do not simply place two current inputs in parallel. A 4-20 mA loop may support series-connected inputs if the transmitter compliance voltage and total burden allow it, or you can use a proper signal splitter or isolator.
Yes. NORVI X includes built-in half-duplex RS-485, and NORVI publishes Modbus RTU master and slave implementation guidance. Confirm the PLC register map, serial settings, addressing and termination before deployment.
NORVI X can acquire data over Modbus or expansion I/O, process and buffer selected values, then publish them using Ethernet, Wi-Fi or optional cellular connectivity. MQTT/MQTTS and HTTP/HTTPS are supported software paths for cloud or server integration.
For suitable non-safety automation, data acquisition and IoT-connected control, NORVI X can operate as the main controller. For a stable brownfield machine, adding NORVI X beside the PLC is often the lower-risk route because the existing validated control system remains unchanged.
Plan the retrofit
Map the PLC, signals and network before you change the panel.
Start with the PLC model, available protocols, required tags, signal types, update rates and site connectivity. Then configure the smallest NORVI X stack that captures the data safely.
