How do you convert Modbus registers to JSON?

Reading the registers is a solved problem — pymodbus, libmodbus or any of a dozen libraries will hand you a list of 16-bit integers in about ten lines. The work is everything after that, because Modbus deliberately carries no semantics: register 40071 is a number, and what it means lives in a vendor PDF.Four things have to be decided before the JSON is correct. Word order: a 32-bit value spans two registers and vendors disagree about which comes first, so the same bytes read as 1,250 or as 81,920,000. Signedness: a temperature below zero read as unsigned becomes 65,486. Scaling: many devices store 234 and mean 23.4, and SunSpec devices put the exponent in a separate register entirely. Units: the same register is watts on one firmware and kilowatts on the next.So the honest answer is that you do not convert Modbus to JSON — you convert Modbus to JSON for a specific device, and that mappin

What is OPC UA telemetry?

OPC UA (IEC 62541) is an industrial communication standard that carries not just values but a model of the equipment producing them. Where Modbus gives you a number at an address, an OPC UA server exposes an address space of typed nodes with names, data types, engineering units, timestamps and quality flags, and you can browse it at runtime without documentation.OPC UA telemetry, in practice, means reading values from that address space — either by polling reads, or by creating a subscription with monitored items so the server pushes changes with a dead-band you specify. Subscriptions are what make it viable at scale: a thousand tags at 100 ms is a lot of polling and very little actual change.It also brings security as a first-class concern rather than an afterthought — X.509 certificates, message signing and encryption, and user authentication are part of the specification. That is genu

How do you normalize industrial data?

Normalizing industrial data means mapping every vendor's tag onto one shared field, and then guaranteeing something about the value behind it. Most projects do the first half and skip the second, which is why the resulting dataset still cannot be queried across machines.The naming layer is what people expect: SPINDEL_AUSLASTUNG, SP LOAD, SLOAD and spindle_load all become spindle_load_pct. It is tedious but conceptually simple, and every plant has a half-finished spreadsheet attempting it.The layer underneath is where the value is, and where the failures are. A canonical field has to carry a unit (feed rate arrives as mm/min, in/min, mm/s, m/s and ft/min — a 25.4x error looks entirely plausible on a chart), a sign convention (half of all power meters report export as positive and half as negative, so a mixed site totals to something quietly wrong), a measurement type (a cumulative counter

What is the difference between Modbus TCP and Modbus RTU?

The data model is identical. Same holding registers, same input registers, same coils, same function codes. Anything that can read one can read the other after a change of framing, and a register map written for RTU is valid for TCP without modification.What differs is the physical and framing layer. Modbus RTU runs over RS-485 or RS-232 — a two-wire multidrop bus, typically 9600 to 115200 baud, with a CRC-16 for integrity and silent-interval framing to delimit messages. Devices are addressed 1 to 247, and there is exactly one master on the bus. Modbus TCP wraps the same protocol data unit in an MBAP header over TCP port 502, drops the CRC because TCP already provides integrity, and allows many concurrent clients.The operational consequences are what matter in practice. On RTU, throughput is shared: one slow or retrying device delays every other device on the loop, and a poll cycle acros

What is the MTConnect protocol?

MTConnect (ANSI/MTC1.4) is a read-only standard for getting data out of manufacturing equipment, and it is the only protocol in common use that ships an opinion about what a machine tool means. It is HTTP and XML — no special client library required — and it is deliberately one-way: MTConnect cannot write to a machine, which is a large part of why plants allow it.The architecture is two pieces. An adapter sits next to the machine and speaks whatever the controller speaks — FOCAS, a serial protocol, a vendor API — and emits a simple key-value stream. An agent consumes that, holds a buffer of recent data, and serves it over HTTP. You then have four endpoints: /probe returns the device model, /current returns the latest value of everything, /sample returns a range by sequence number, and long-polling /sample gives you a stream.The semantic part is the DataItem dictionary. Every value is cla

How do you connect a PLC to an AI model?

Mechanically it is three hops: get the tags off the PLC, turn them into something with stable names and units, and expose that to the model. The first and third hops are well-trodden. The middle one is where projects stall.Getting tags off. A Siemens S7 is reachable over S7comm on TCP 102 or over the OPC UA server in newer firmware. A Rockwell Logix controller exposes named, typed tags over EtherNet/IP. A generic PLC almost always speaks Modbus TCP. All three are solved by existing libraries; none of them requires anything clever.The middle hop. What comes off the PLC is DB100.DBD24 or Tag_47 or register 40071. A model cannot reason about that, and neither can a person six months later. Worse, the same physical measurement on the machine next to it is called something else, so anything the model learns about one machine does not transfer. This is the actual work: stable names, declared u

What is SunSpec Modbus?

SunSpec is an information model layered on top of Modbus, not a replacement for it. A SunSpec-compliant device still speaks ordinary Modbus TCP or RTU; what SunSpec adds is agreement about which registers hold what.A device exposes a chain of numbered models starting at a well-known base address, each with a fixed layout. Model 1 is common identity — manufacturer, model, serial, version. Model 101/102/103 are single-phase, split-phase and three-phase inverters. Models 201 to 204 are meters. Model 124 is storage and 802 is a battery. You read the chain, learn what the device is, and know the register layout without a vendor PDF. For a fleet of mixed inverters that is a genuine improvement.The sharp edge is the scale factor. SunSpec stores values as integers and puts the decimal exponent in a separate register — so W might read 4120 with W_SF reading -1, meaning 412.0 W. Code that reads th

How do you monitor a CNC machine remotely?

Start with what the controller will give you, because that decides everything downstream. A Haas exposes MTConnect natively on recent control generations. A Fanuc needs FOCAS — either a licensed library talking to the control, or an MTConnect adapter in front of it. A Siemens 840D is reachable over S7comm or the OPC UA server on newer firmware. Okuma, Mazak, DMG Mori and Brother each have their own combination, and most modern controls offer OPC UA as well.The values worth collecting are few and consistent: spindle load (rising at constant feed and speed means a dulling tool; a step change means a collision), spindle speed and feed rate for context, execution state for utilisation, part count for throughput, program name so anything you measure can be attributed to a part number, and alarm code.Getting it out of the plant is a network conversation more than a technical one. Keep the coll

What is MCP (Model Context Protocol)?

MCP — the Model Context Protocol — is an open standard for letting a language model call external tools and read external data through one consistent interface. Instead of every application inventing its own plugin format, an MCP server describes its tools once and any MCP-capable client can discover and call them.The shape is simple. A server advertises tools (things the model can call), resources (things it can read) and prompts. The client — an assistant, an IDE, an agent framework — connects, lists what is available, and calls what it needs. Transport is typically Streamable HTTP; the older SSE transport is being retired.For industrial data this matters more than it might sound, because the alternative is bad in a specific way. Without MCP, giving an assistant access to machine telemetry means writing a bespoke integration per assistant, and each one needs to be told the shape of you

How do you read data from a Fanuc controller with FOCAS?

FOCAS (Fanuc Open CNC API Specification) is the library Fanuc provides for reading and writing controller data over Ethernet. It is a C library with a long list of functions — cnc_rdspeed for spindle and feed, cnc_rdprgnum for the active program, cnc_rdalmmsg for alarms, cnc_rdparam for parameters — and it is the most direct path to a Fanuc control.There are three practical routes. FOCAS directly gives you everything and requires the library, a licence for it, and a host that can load it. An MTConnect adapter in front of FOCAS is the common production pattern: the adapter handles the library, and you consume ordinary HTTP and XML. OPC UA is available on newer controls and avoids FOCAS entirely, at the cost of a different model to map.The trap is not the API — it is what comes out of it. In the corpus, Fanuc spindle speed appears under 29 distinct spellings: ACT SP SPEED(RPM), ACTSPSPEED

Answers — industrial telemetry, protocols and normalization

How do you convert Modbus registers to JSON?	Reading Modbus registers is the easy part. Turning them into typed, named JSON with correct units an…
What is OPC UA telemetry?	OPC UA telemetry, what makes it different from older industrial protocols, and the one thing it does…
How do you normalize industrial data?	What normalizing industrial telemetry actually involves — naming, units, sign conventions and bounds…
What is the difference between Modbus TCP and Modbus RTU?	Same registers, same function codes, completely different operational life. What changes between Mod…
What is the MTConnect protocol?	MTConnect explained: the agent/adapter architecture, the semantic dictionary for machine tools, and …
How do you connect a PLC to an AI model?	The practical path from a PLC tag to a model or an agent — and the data-layer problem that sits in t…
What is SunSpec Modbus?	SunSpec explained: standard register models for inverters, meters and storage — and the scale factor…
How do you monitor a CNC machine remotely?	Getting spindle load, feed rate and part count off a CNC and out of the plant — the options per cont…
What is MCP (Model Context Protocol)?	MCP explained for industrial data: what it is, what it replaces, and why it matters for machine tele…
How do you read data from a Fanuc controller with FOCAS?	Reading spindle, feed, program and alarm data off a Fanuc control via FOCAS — the options, the licen…