Senbrix Devlog Series Index - Six Posts on Building a Raspberry Pi Soft PLC

Senbrix is a soft PLC that runs on a Raspberry Pi. Ladder and C# live in one program, and an AI sits on top. These six posts trace it from an old annoyance built up over 18 years of industrial automation contract work, all the way to an AI writing ladder and catching a fault on a running PLC.

Raspberry Pi, ladder, C#, AI. Four things that have no business being in the same box, thrown in together anyway. Whether that turns into a monster or something usable, read in order and find out.

Why, and how it was designed

The start and the design. What hurt, and what structure was chosen to fix it.

• Senbrix Devlog Part 1 - So I Decided to Build a PLC Myself Getting PLC data to a server always meant standing one more PC next to it. That grind met the strange convenience of AI coding, and the answer was to fold Raspberry Pi, ladder, C#, and AI into one thing.
• Senbrix Devlog Part 2 - Designing the PLC Ladder is a circuit. Pull every path, AND them, OR them. A fixed 10 ms ladder loop next to a free-running C# loop, the editor, AI, and runtime that make up the system, and how they talk to each other.

Write it, then run it

The implementation. How ladder and C# actually end up in one program, and how that program runs on a Pi.

• Senbrix Devlog Part 3 - Calling C# from PLC Ladder Logic A product counter that reports to a server when it hits target. Five memory areas, address suffixes that decide the type, sixteen ladder functions, and the one rule that turns an unknown function name into a C# call.
• Senbrix Devlog Part 4 - The Ladder Runs on a Raspberry Pi A fixed cycle, downloads without power-off, values that survive an outage, auto-start, and one bug not killing the controller. The five reasons people trust a PLC, checked one by one on a .NET runtime running on real hardware.

The AI writes it, the AI fixes it

The AI workflow. Where a human still gives the orders, filters the output, and signs off.

• Senbrix Devlog Part 5 - I Had an AI Write the Ladder Ask for an intersection traffic light, get 85 rungs of ladder. A DSL that round-trips ladder as text, a rule to use only what the docs confirm, four layers of checks from build to human review, and the approval gates a human holds.
• Senbrix Devlog Part 6 - I Let the AI Diagnose the PLC One contact flipped on purpose, one line describing the symptom. An observation order, an arming step that acts as permission, six reproduction experiments with predictions written first, a five-field report and a four-field history. Writes open only inside what a human allowed.

How to read this series

Start at Part 1 and go in order, and you get the full loop from why it exists to the AI fixing a fault. If you only care about the implementation, jump to Parts 3 and 4. If you only care about the AI side, Parts 5 and 6. Each part reuses the examples and rules of the one before it.

• What this PLC is and where to get it: Senbrix product overview.
• Building ladder and HMI screens together with AI: Building PLC Ladder and HMI Screens with AI.