Decisions

2026-09-14 · A static site generated from Markdown, deployed automatically from GitHub.

2026-08-27 · If PicoDCC's PIO program runs out of packet data, it keeps emitting valid DCC '1' bits rather than parking the output pin. Running short of packets costs throughput instead of putting DC on the rails.

2026-08-26 · Connecting to the command station checks the power state instead of switching it on. Only an operator turns the track on.

2026-08-25 · Off-the-shelf detectors pull low for occupied, so a broken wire under the layout reads as a clear block. A home-designed board with an active-high output makes that fault read as occupied instead.

2026-08-24 · Powering an LM-iD.1's Input A, as every datasheet says to, makes its output idle at 5V into 3.3V expander inputs. It's deliberately left unpowered on Westgate Hollow.

2026-08-24 · Sensors and point feedback talk to the orchestrator over MQTT under a binding contract. Operator devices, including the handheld throttle, use the orchestrator's WebSocket control plane.

2026-08-24 · Cobalt iP point motors take DCC commands but can't report their position, so position comes from their S2 contacts on a feedback node. That catches hand-thrown points, but creates two mappings nothing cross-checks.

2026-08-24 · The ESP32 throttle speaks both WiThrottle (to JMRI) and the orchestrator's WebSocket, as equal peers selectable from its settings screen. With no over-the-air updates, a compile-time switch would mean a cable at the layout.

2026-08-23 · An unwired expander input reads as "clear", so publishing the whole pin table would tell the orchestrator a block is empty using a wire that doesn't exist. Nodes publish an allow-list instead.

2026-08-16 · Every sensor re-sends its reading at least every 30 seconds. A silent sensor degrades only its own blocks, while a garbled message Safe-Stops the layout.

2026-08-13 · Instead of describing the railway twice by hand, as a drawing and as a graph, the drawing is compiled into the graph. The operator reviews the diff and applies it.

2026-08-08 · Automated braking uses only measured track lengths and refuses on unmeasured track. Automation's one invariant is that a train never passes the end of its authority, and where a beam is fitted, the beam breaking is what stops it.

2026-05-02 · A retained MQTT control message replays to every client that reconnects, which would make a loco move with nobody asking. Control topics are always published unretained.

2026-05-02 · If sensor, block, MQTT or DCC state becomes unknown, automated movement halts and an operator has to recover it. The system never guesses where a train is.

2025-10-20 · Saving settings to flash stops DCC output for about 410ms, which makes decoders run away at full speed. So writes are only allowed with the main track off, in a mode entered from the command station's own screen.

2024-04-27 · Westgate Hollow Yard is a deliberately small OO gauge goods yard for proving the control system and practising, ahead of a larger full-room layout.