Reference Guides
Complete technical documentation for every GOPLC subsystem. Architecture diagrams, function signatures, parameter tables, and IEC 61131-3 Structured Text examples — for every hardware target, every industrial protocol, every built-in library.
Guides are hosted on goplc.app — click any card to read.
Getting Started
Start here — the complete manual and the first-time walkthrough
Complete Manual
The full reference — every subsystem, every config key, every ST function. 41,000 lines across 65 chapters. Start here for the whole picture.
Getting Started
Install, create a project, write your first ST program, connect to a device, deploy. The shortest path from zero to a running PLC.
Platform
Core development tools, distributed execution, security, and resilience
IDE & Runtime
Browser IDE, task scheduler, debugger with breakpoints + stepping, HMI builder, project files, protocol analyzer.
Visual Ladder Editor
Rung-based LD editor with XIC/XIO/OTE/OTL/OTU + TON/TOF/TP timers. Compile-validate-deploy-online. Click-to-force in live mode.
AI Assistant
Chat + autonomous control mode, 13 runtime tools, Claude/OpenAI/Ollama, code/HMI/flow generation, voice input.
Configuration
Every YAML field documented — tasks, protocols, I/O mapping, DataLayer, AI, Node-RED, real-time, fleet, security.
System & Resilience
Hardware watchdog, crash-safe RETAIN with atomic writes and rolling backups, UPS monitoring (NUT/apcupsd), graceful shutdown chain.
Authentication & RBAC
Role-based access control with 4 roles, JWT authentication, audit trail, and 21 CFR Part 11 electronic signatures for regulated industries.
Alarm Management
ISA-18.2 alarm engine with 8 alarm types, state machine, shelving, deadband, delay, auto-ack, and HMI annunciator integration.
Edge Historian
Per-scan sampling with deadband, 3-tier decimation, log-all opt-in, InfluxDB and MQTT forwarders, burst capture on alarm.
Hot Standby & Failover
Active/standby redundancy with UDP heartbeat, full + incremental state sync, PID bumpless transfer, split-brain prevention.
Clustering
Boss/minion architecture, DataLayer pub/sub, fleet management, tested to 500 minions.
Node-RED
7 custom GoPLC nodes, Dashboard 2.0, AI-generated flows.
REST API
250+ endpoints — runtime control, variables, programs, tasks, protocols, licensing, diagnostics.
MCP Server
80 tools for AI assistants — Claude Code, Cursor, Windsurf. Programs, tasks, variables, HMI, debugger, fleet, protocol analyzer.
Protocol Analyzer & Store-and-Forward
Packet capture, PCAP export, offline buffering with automatic replay on reconnect.
ST Language & Libraries
Built-in functions callable from Structured Text — data processing, integration, and fault tolerance
Timers, Counters & FBs
TON, TOF, TP, RTO, CTU, CTD, CTUD, SR, RS, R_TRIG, F_TRIG, PID, PIDE.
Math, String & Conversion
150+ functions — trig, statistics, EMA/SMA, string ops, type conversions, bitwise, unit conversions.
JSON
Parse, build, query, modify JSON. Dot-path access, typed getters, JSONPath.
HTTP Client
GET/POST/PUT/DELETE from ST. Response maps, custom headers, webhooks.
File I/O
Read/write/append files, line-by-line processing, CSV logging. Sandboxed.
Database
SQLite, PostgreSQL, MySQL. Query, insert, transactions, schema management.
Data Structures
ARRAY, MAP, LIST, QUEUE, STACK, DEQUE, SET, HEAP/PQUEUE.
Resilience & Caching
Cache, circuit breaker, rate limiter, throttle, debounce, bulkhead, hysteresis.
Debug & Logging
Multi-target logging: file, SQLite, PostgreSQL, InfluxDB, syslog, console.
Cryptography
Hashing, HMAC, encryption, key derivation, certificates, TLS from ST.
Regular Expressions
Pattern matching, search, replace, capture groups in Structured Text.
CSV & INI Parsing
Read/write CSV and INI config files from Structured Text.
SMTP Email
Send email alerts and notifications directly from Structured Text.
Motion Control
PLCopen MC function blocks — axis lifecycle, homing, jog, absolute/relative moves, multi-axis.
OSCAT Library
OSCAT-compatible function blocks — HVAC, building automation, date/time, signal processing.
Industrial Protocols
First-class client and server implementations for every major automation protocol
Modbus TCP
Client + server, FC01-FC16, multi-device polling.
Modbus RTU
Client + server, RS-485, bus scanning, RTU-over-TCP bridge.
EtherNet/IP
Scanner + adapter, tag browsing, Allen-Bradley integration.
Siemens S7
Client + server, DB/I/Q/M areas, S7-300/400/1200/1500.
OPC UA
Client + server, node browsing, security policies.
MQTT
Client + built-in broker, pub/sub, message queue, QoS.
Omron FINS
Client + server, DM/CIO memory areas, CJ/NJ/NX series.
DNP3
Master + outstation, BI/BO/AI/AO/counter, SCADA/utility.
IEC 104
Client + server, SP/DP/float/scaled/counter, power grid.
BACnet
Client + server, priority array, COV, WhoIs, HVAC/BMS.
SNMP
Client + agent + trap receiver, OID helpers, datacenter monitoring.
DF1
Client, SLC 500 / MicroLogix, N7/F8/B3 file addressing.
Sparkplug B
Edge node, NBIRTH/NDATA lifecycle, Ignition integration.
SEL Relay
Client + server + meter. Mirrored bits, SER, oscillography, COMTRADE, settings.
CAN Bus
SocketCAN raw frames + CAN FD, J1939 PGN decoder, OBD-II passenger-car PIDs, DBC file decoder.
InfluxDB
Write + batch, line protocol, Grafana dashboards.
Hardware Interfaces
Native Linux SBC support plus microcontroller bridges for anything periph.io can't reach
HAL (native Linux SBCs)
Declarative pin manifest for Raspberry Pi, Orange Pi, and similar — rpi_gpio, PCF8574, Grove ADC, DHT, ADXL345.
Direct GPIO
Imperative pin access from ST — GPIO_READ/WRITE/TOGGLE + I2C_SCAN. For prototyping and diagnostics.
Parallax P1
Propeller 1 (P8X32A) — GPIO, SPI, UART, I2C, PWM, servo, frequency counter, quadrature + step-dir encoder.
Parallax P2
Propeller 2 (Rev G) — 82 functions, smart pins, UART, I2C, SPI, ADC/DAC, PWM, servo, encoder, OLED.
Arduino
Uno R4 WiFi — GPIO, 14-bit analog, PWM, DAC, I2C, servo, WiFi, BLE, LED matrix, HC-SR04.
Teensy
Teensy 4.0 — CAN bus, hardware PID, complementary PWM, NeoPixel, encoder, RTC, TRNG, SPI, UART.
Flipper Zero
NFC, RFID (125 kHz), Sub-GHz radio, infrared, iButton, GPIO.
RP2040-Zero
Waveshare RP2040-Zero — GPIO, ADC, PWM, NeoPixel, I2C, SPI, UART, servo, OLED, distance, temp.
ESP32 HMI Dongle
ESP32-S3-LCD-1.47 — WiFi status display + USB mass storage. mDNS discovery, OTA updates.
Phidgets
Phidgets USB — voltage, current, temperature, humidity, load cells, relays, motors.
Specialty
Vertical-specific integrations — CNC and laser, GPS, entertainment lighting, events
G-Code
File I/O, line parser, machine connection, status, pause/resume/stop. xTool HTTP, GRBL serial, Marlin serial.
NMEA & GPS
GPS position, speed, heading, satellite info from NMEA serial streams.
Entertainment & Show Control
Art-Net DMX, audio, video, lighting scenes, cue sequencing for show control.
Specialized Utilities
Scheduling, unit conversion, geofencing, alarm management, and other utility functions.
Event Bus & Webhooks
Event types, webhook delivery, MQTT publishing, DLQ, Slack/PagerDuty routing.
Ready to Build?
Download GOPLC, open a project, and you'll have every one of these subsystems running in minutes.