BigFred hub on Raspberry Pi 5 — reference deployment
This document set describes the reference production setup for connecting BigFred to a DCC command station and operating it as a multi-user throttle hub on a model railroad.
Hardware is commercial off-the-shelf only — no custom LocoNet electronics.
Officially supported command stations
| Model | Manufacturer | Recommended BigFred link | Notes |
|---|---|---|---|
| DR5000 | Digikeijs | loconet_serial + Uhlenbrock 63120 on LocoNet-T |
§2–§6 |
| RB1110 / RB1110-Mini | RailBOX | z21 UDP on LAN/WiFi |
§7 Z21 — not Uhlenbrock 63120 |
| Other centrals with Z21 and LocoNet | various | Usually z21 if vendor documents PC control |
Best-effort — no guarantee — §7.5 |
Other LocoNet-only masters may work with the Uhlenbrock 63120 path if they behave as a LocoNet master; they are outside official support until validated on your layout.
Two connection paths
LocoNet serial (DR5000) — §2–§6
flowchart LR
O[Drivers] -->|HTTP/WS| BF[BigFred Pi 5]
BF <-->|USB 57600| U6[Uhlenbrock 63120]
U6 <-->|RJ12 LocoNet| CS[DR5000]
CS --> DCC[Layout]
Z21 UDP (RB1110) — §7
flowchart LR
O[Drivers] -->|HTTP/WS| BF[BigFred Pi 5]
BF <-->|UDP 21105| CS[RB1110]
CS --> DCC[Layout]
Reference stack (common host)
| Layer | Choice |
|---|---|
| Host | Raspberry Pi 5 (8 GB RAM recommended) |
| Storage | NVMe SSD via M.2 HAT+; RO / + RW /data on hub image |
| OS | Buildroot hub image (production) or Pi OS 64-bit (dev) — §8 |
| OS tuning | PREEMPT_RT, CPU isolation, hardware watchdog |
| To DR5000 | Uhlenbrock 63120 on USB 3 → loconet_serial @ 57600 8N1 |
| To RB1110 | LAN/WiFi → z21 @ UDP 21105 (no Uhlenbrock 63120) |
| Application | BigFred loco-server + dcc-bus |
Scope
| In scope | Out of scope |
|---|---|
| Pi 5 + hub OS image (Buildroot) | DIY LocoNet interface |
| NVMe layout, RT, fanctl, Alloy | Full Buildroot fork maintenance |
| Uhlenbrock 63120 + LocoNet path (DR5000) | Custom MCU firmware |
| Z21 path (RB1110, dual-protocol notes) | Building a command station |
| BigFred hub + driver limits | Every unsupported central model |
| Bring-up and diagnostics | LCC, XpressNet-only centrals |
Overview & architecture
LocoNet electrical & wiring
DR5000 / Uhlenbrock 63120 path.
Host platform (Pi 5)
BOM, Pi OS interim path.
Uhlenbrock 63120
BigFred integration
loconet_serial and z21.
Bring-up & testing
Z21 connection
RB1110, dual-protocol centrals.
Hub OS image
Buildroot, partitions, RT, make image.
Authoritative references
- Drivers:
loconet_serial.go,z21.go,driver.go. - Z21 protocol:
docs/bigfred/protos/z21.md. - LocoNet protocol:
docs/bigfred/protos/loconet.md. - WiThrottle protocol:
docs/bigfred/protos/withrottle.md. - DCC bus:
16-dcc-bus/. - Centrals: Digikeijs DR5000, RailBOX RB1110.
LocoNet message formats are © Digitrax; Z21 is © Roco/Fleischmann. This documentation is for educational purposes.