SPC Addon API

Build custom function block nodes for Stored Program Controls — the Siemens LOGO!-inspired industrial automation mod for Minecraft.

API 1.1.2 NeoForge 1.21.1 Java 21

TL;DR — Your first addon in 3 steps

You need 3 Java files (~80 lines total) and 1 config entry to create a working addon node. Follow the learning path below — you can have a custom node running in under 30 minutes.

Recommended Learning Path

Follow these pages in order. Each one builds on the previous.

Getting Started Beginner

Set up your project, add the API jar, configure your mod descriptor.

~10 min

Core Concepts Beginner

Understand nodes, ports, signals, execution phases, and how the runtime works.

~15 min

Your First Addon Beginner

Hands-on: build a complete Daylight Sensor node from scratch — copy-paste ready.

~15 min

After completing the 3 steps above, your addon will work!

The guides below go deeper — read them when you want to build more advanced nodes.

Creating Custom Nodes Intermediate

Deep dive into schemas, ports, parameters, factories, and execution phases — with 4 full examples.

~20 min

Node Categories Intermediate

Organize your nodes with custom categories, icons, and sort order in the editor palette.

~10 min

State & Persistence Intermediate

Build timers, counters, and toggles with persistent state slots and double buffering.

~15 min

Signal Processing Intermediate

Read, write, convert, and transform signals — scalers, clamps, multiplexers, and more.

~15 min

What Can You Build?

The SPC Addon API lets other NeoForge mods add custom function block nodes to the in-game LOGO programming editor. Your nodes appear in the palette, can be wired to other blocks, saved in programs, and run by the LOGO runtime — just like built-in ones.

What you want to do	Difficulty	Page to read
Add a sensor, logic gate, math block, or actuator	Beginner	Your First Addon + Examples
Deep-dive into node schemas, ports, and parameters	Intermediate	Creating Custom Nodes
Organize nodes with custom categories and icons	Intermediate	Node Categories
Build timers, counters, or toggles with state	Intermediate	State & Persistence
Transform, scale, or multiplex signals	Intermediate	Signal Processing
Understand when/how your node executes	Beginner	Core Concepts
Read world data (weather, time, light, entities)	Beginner	Execution Context
Use different data types (numbers, text, items)	Beginner	Signal Types
Bridge to another mod (Create, Mekanism, etc.)	Intermediate	Context Extensions
Add physical blocks to the LOGO machine	Advanced	Multiblock Modules
Add wireless devices or network cables	Advanced	Network Devices
React to program start/stop events	Intermediate	Runtime Events

Essential Pages

🚀

Getting Started Beginner

Set up your project, add the API dependency, configure your mod descriptor, and get building.

📐

Core Concepts Beginner

Understand execution phases, signal types, the node lifecycle, and how everything fits together.

🔧

Your First Addon Beginner

Step-by-step walkthrough: build a complete custom sensor node from scratch in under 100 lines.

💡

Examples Beginner

7 complete, copy-pasteable examples: AND gate, counter, rain sensor, threshold, display, and more.

Go Deeper — When You Need Them

🧩

Creating Custom Nodes Intermediate

Schemas, ports, parameters, factories, execution phases — everything about node creation with 4 examples.

🏷️

Node Categories Intermediate

Custom categories, icons, sort order — organize your nodes in the editor palette.

💾

State & Persistence Intermediate

Persistent slots, double buffering, global markers — build timers, counters, and stateful nodes.

🔀

Signal Processing Intermediate

Read, write, convert, and transform signals — scalers, clamps, multiplexers, and type conversions.

⚡

Signal Types & Domains Beginner

The 6 data types, conversion rules, constants. Read this when you work with non-digital signals.

🖥️

Execution Context Beginner

All 37 built-in methods for reading world state. Look up what data your node can access.

🔌

Context Extensions Intermediate

Need data from another mod? Create a custom bridge for cross-mod compatibility.

📢

Runtime Events Intermediate

Hook into program start/stop and multiblock assemble/disassemble. For reactive addons.

Advanced Features

🧱

Multiblock Modules Advanced

📡

Network Devices Advanced

Wireless transmitters, receivers, activation signals. Requires understanding BFS discovery.

Reference

🗄️

Registries

All 5 registries in detail — for when you need to know exact method signatures and freeze behavior.

📚

API Reference

Every class, interface, method, and enum — fully documented. Use as a lookup, not a read-through.

❓

FAQ

Common questions: registration timing, save compatibility, debugging, state persistence.

How It Works — At a Glance

Your addon depends on the lightweight API jar at compile time. It contains only interfaces and records — no implementation. At runtime, the full SPC mod provides everything. Players need SPC installed alongside your addon.

Node Lifecycle Overview

Define a Schema Declare your node's unique type ID, execution phase, input/output ports, and any configurable parameters using SpcNodeSchema.
Implement the Compiled Node Write a class that implements ISpcCompiledNode. This is the per-tick executable logic: read inputs, compute, write outputs.
Create a Factory Implement ISpcNodeFactory to construct compiled node instances during program compilation. The factory receives all resolved addresses and parameter values.
Register Call SpcNodeRegistry.register(schema, factory, category) in your @Mod constructor. Done!
Play! Your node appears in the LOGO editor palette. Players place it on the canvas, wire it to other blocks, and run programs.

💡 Ready to jump in?

Head to Getting Started to set up your project, or straight to Your First Addon if you already have a NeoForge mod ready.

Next → Getting Started