Basic
MQTT
A lightweight publish/subscribe protocol operated through a broker.
In industrial practice
It is widely used for IIoT telemetry, events and edge-to-cloud integration.
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TECHNICAL GLOSSARY
Industrial automation
Protocols, signals and factory-floor buses: MQTT, Modbus, CAN, RS-485 and 4–20 mA, with what each requires in practice.
terms in this category
Intermediate
MQTT QoS
MQTT delivery guarantees: at most once, at least once or exactly once.
In industrial practice
Higher QoS increases traffic and state; choose it according to the consequence of loss or duplication.
Related:MQTT
Intermediate
TWAI/CAN
TWAI is the classic-CAN-compatible implementation found in certain ESP32 families.
In industrial practice
The internal controller still needs a CAN transceiver and physical termination.
Do not confuse
Do not confuse the TWAI controller with a ready-made CAN interface.
Related:CANBus termination
Intermediate
CAN
A robust differential multi-master bus oriented around messages and arbitration.
In industrial practice
It is common in machines and vehicles; it requires a transceiver, termination and an ID strategy.
Related:TWAI/CANBus termination
Basic
RS-485
A differential electrical standard for multipoint serial communication.
In industrial practice
It defines the physical layer, not message content; Modbus RTU is frequently carried over it.
Do not confuse
RS-485 is not synonymous with Modbus.
Basic
RS-232
A point-to-point serial standard with positive and negative electrical levels.
In industrial practice
Do not connect it directly to a 3.3 V GPIO; use a transceiver such as the MAX3232.
Basic
Modbus RTU
A binary master/server protocol normally carried over RS-485.
In industrial practice
It requires correct address, baud rate, parity, register and timing definitions.
Related:RS-485Modbus TCP
Basic
Modbus TCP
Modbus transported over TCP/IP, normally on port 502.
In industrial practice
It does not use the Modbus RTU CRC; reliability and security depend on the network architecture.
Related:Modbus RTUEthernet
Advanced
OPC UA
An industrial standard for semantic modeling and secure data exchange.
In industrial practice
The ESP32 usually acts through a gateway because a complete stack may require additional resources and certification.
Related:MQTTModbus TCP
Intermediate
4–20 mA
An analog current standard in which 4 mA represents live zero and 20 mA represents full scale.
In industrial practice
The ESP32 needs a shunt resistor, protection and conditioning compatible with its ADC.
Related:ADC0–10 VGalvanic isolation
Intermediate
0–10 V
An analog voltage signal standard used in drives, actuators and instrumentation.
In industrial practice
The ESP32 input cannot tolerate 10 V; use a calculated divider, buffer and protection.
Intermediate
PNP e NPN
Sensor output topologies that source or sink current.
In industrial practice
The input interface must be designed for the selected standard and industrial voltage.
Related:OptocouplerDry contact
Intermediate
Bus termination
An impedance installed at the ends of a transmission line to reduce reflections.
In industrial practice
CAN and RS-485 normally use termination at both ends, not at every node.
Related:RS-485CANRS-485 biasing
Advanced
RS-485 biasing
Resistors that establish a known state when no transmitter drives the bus.
In industrial practice
Values and placement must account for terminations and fail-safe transceivers.
Related:RS-485Bus terminationFail-safe
Advanced
Fail-safe
The principle of bringing a system to a safe state when a failure occurs.
In industrial practice
The safe state depends on risk analysis and must not rely only on ESP32 firmware.