5. BigFred integration

BigFred connects via a command-station catalogue row (kind + connection_uri). The Pi 5 host is the same; the kind depends on the central — see §1.2.

Central	Kind	Details
DR5000	`loconet_serial`	§5.1–§5.5 below (Uhlenbrock 63120)
RB1110	`z21`	§7
Other Z21 + LocoNet	`z21` or `loconet_serial`	Best-effort — §7.5

5.1 LocoNet serial — serial device (DR5000)

Link	Device path
Uhlenbrock 63120 → Pi 5 USB 3	`/dev/ttyACM0` (typical)
After udev rule (§3.5)	`/dev/loconet-63120`

Pin the path with a udev rule on the Uhlenbrock 63120 USB VID/PID. Add the service user to group dialout.

5.2 LocoNet serial — connection URI

pkgs/bigfred/dcc-bus/service/station/driver.go:

Field	Value
Kind	`loconet_serial`
URI	`serial:///dev/loconet-63120:57600`
Speed steps	`128`

Prerequisite: LNCV 57600 + LocoNet Direktmodus on Uhlenbrock 63120 (§4.2).

5.3 LocoNet — catalogue and daemon

Command stations are admin-only (command_station.go):

Create e.g. DR5000 (LocoNet), kind loconet_serial, URI as above.
Attach to a layout (POST /api/v1/layouts/{id}/command-stations).
dcc-bus opens the serial device (--station-kind loconet_serial).

5.4 LocoNet — driver limits

loconet.go: speed/dir, F0–F28 (F0–F8 via slot DIRF/SND, F9–F28 via OPC_IMM_PACKET), observe (incl. F9–F28), and CV read/write on the programming track (service-mode direct byte). No F29+, no POM CV (RailCom), no accessory/sensor control over LocoNet.

5.5 Z21 — catalogue and daemon (RB1110)

Field	Value
Kind	`z21`
URI	`udp://192.168.x.x:21105` (RB1110 IP; port defaults to 21105)
Speed steps	`128`

Full setup: §7. Broader function/CV surface in z21.go.

5.6 Multi-user hub (both kinds)

sequenceDiagram participant D1 as Driver A participant D2 as Driver B participant BF as BigFred dcc-bus participant IF as Uhlenbrock 63120 or Z21 UDP participant CS as Command station D1->>BF: subscribe loco 3, setSpeed BF->>IF: station protocol IF->>CS: central CS-->>IF: state push / bus IF-->>BF: updates BF-->>D1: loco.state

One dcc-bus daemon per (layout × command station).
Sessions, takeover, shared observation — same hub semantics.
LocoNet: MultiMaus on the bus; Z21: LAN_X_LOCO_INFO push path.

5.7 Operational rules

Rule	LocoNet	Z21
Single writer	Do not open serial with minicom/JMRI	Avoid second Z21 master app
Hardware	One Uhlenbrock 63120 per `loconet_serial` row	Stable IP; UDP 21105 open
Host	NVMe root (§3)	Same
RB1110	Do not use Uhlenbrock 63120 for supported path	Use `z21` only

Continue with §6 Bring-up or §7 Z21.