LearnSCADASim-22

A hosted simulator can answer Modbus TCP. It can never answer a serial

master. Yet much of the field still talks RTU over a twisted pair:

drives, power meters, flow computers and older remote terminal units.

When a serial link fails, it fails on framing, timing and port settings,

and the only way to learn those failures is to put a real device on the

other end of the wire.

LearnSCADASim-22 builds that device. On a Luckfox Pico Ultra W you will

build a small appliance that serves twenty Modbus TCP sessions over

Ethernet, each on its own configurable port, plus one RTU master on an

isolated RS-485 port and one ASCII master on an RS-232 port, all at the

same time and all from one shared datastore. Load any device from its

published register map through a web dashboard over Ethernet or WiFi,

and the device exists.

Every part of the book produces something that works. You write a

testable specification, choose and wire the hardware, put a hardened

Linux image on the board that survives being unplugged, and turn on the

serial ports in the device tree. Then you write the simulation engine:

the datastore and its behaviors, the TCP, RTU and ASCII servers, the

session manager that enforces the twenty-two slots, and fault injection

that breaks the link on purpose. The web interface adds a live register

view, port settings, map upload, a session list and a frame viewer.

Finally you load test the appliance at full budget and prove it against

Ignition, Modbus Poll and Python before packaging a release image.

What you will learn:

- Write requirements a test can fail, and trace each one to its proof

- Wire isolated, auto-direction RS-485 and an RS-232 DB9 port to 3.3 V

UARTs safely

- Enable UART3 and UART4 in the RV1106 device tree and settle pin

multiplexing

- Harden Ubuntu with a read-only root against power cuts and flash

wear

- Frame Modbus RTU and ASCII correctly: CRC, LRC, t1.5 and t3.5

- Serve twenty TCP sessions on one core without starving the serial

ports

- Load any device from its register map, several units on one trunk

- Inject bad CRCs, delays, exceptions and silence on purpose

- Build a browser dashboard, frame viewer, users and backup

- Load test, troubleshoot and package a release image

Written for automation technicians, integrators, controls engineers,

students and trainers who know what a holding register is and want to

build what sits behind one. Fully illustrated with detailed technical

diagrams, every requirement numbered and every build step backed by

copy-paste commands. A companion to Understanding Modbus, PLCSIM

Edition.