Two digital command stations, two philosophies — the facts side by side: protocols, price, feedback and ModelRailPro connection.
The black Z21 (Roco/Fleischmann, art. 10820) is a ready-to-run manufacturer product: plug in and drive, with a factory warranty and manufacturer support. DCC-EX (EX-CommandStation) is an open-source project you build yourself on an Arduino Mega, ESP32 or STM32 — strong on price, flexible in configuration, but dependent on community support via forum and Discord. Both command stations work with ModelRailPro, but they make very different demands on the user.
The choice comes down to three questions: which protocols do I need, what is my budget, and how much do I want to configure myself? The comparison below helps you decide based on verified specs — no marketing claims.
| Z21 black (art. 10820) | DCC-EX (EX-CommandStation) | |
|---|---|---|
| Type | Ready-to-run, factory product | Open-source DIY or RTR kit |
| Protocol | DCC (14/28/128 steps) + Motorola MM I/II | DCC only (14/28/128 steps) |
| mfx | Not supported | Not supported |
| RailCom cutout | Yes | Yes (ESP32 + EX8874, v5.6.0, 2026) |
| RailCom feedback | Yes (via R-BUS / CAN) | To be confirmed on a layout |
| Feedback buses | R-BUS (max. 160 blocks), CAN, LocoNet, X-BUS | GPIO pins / EXRAIL (no R-BUS/LocoNet) |
| Track current | 3 A, 12–24 V adjustable | Depends on motor shield |
| ModelRailPro connection | UDP 21105 (Z21 LAN) | TCP 2560 (Wi-Fi/Ethernet) or USB serial |
| Guide price | ~€250–350 (indicative) | DIY ~€25–60 / RTR ~€80–150 (indicative) |
| Support | Factory warranty (Roco/Fleischmann) | Community (forum, Discord) |
The black Z21 delivers 3 amperes of track current, adjustable between 12 and 24 V. It supports DCC with 14, 28 or 128 speed steps and Motorola MM I and II — useful if you also want to run older Märklin locos that only have a Motorola decoder. A common misconception: no Z21 model supports mfx. For mfx auto-registration you need a Märklin CS2 or CS3.
For feedback the Z21 offers several buses: R-BUS (maximum 160 blocks), CAN, LocoNet and X-BUS. The station generates a RailCom cutout so that RailCom decoders can report back their position. ModelRailPro connects via the Z21 LAN protocol on UDP port 21105.
Model differences: the white z21 presumably connects via Wi-Fi only (no separate LAN port) and has no separate programming track. Whether the white z21 has LocoNet is to be confirmed on a layout. The z21 start also lacks the extra connectors. Anyone wanting R-BUS or LocoNet feedback should choose the black Z21.
Guide price black Z21: approx. €250–350 (indicative; prices vary by dealer and timing).
DCC-EX runs on an Arduino Mega, ESP32 or STM32 with a motor shield (e.g. L298N or EX8874). You build it yourself or buy a pre-assembled RTR kit. Protocol: DCC only. Older Motorola locos will not run unless fitted with a DCC decoder.
A RailCom cutout is available on the ESP32 + EX8874 motor shield combination (EX-CommandStation version 5.6.0, released 2026). Full RailCom feedback — where decoders actively send their address back to the station — is in development and is to be confirmed on a layout. Feedback currently runs via EXRAIL logic and GPIO pins; R-BUS and LocoNet are not present.
ModelRailPro connects via TCP port 2560 (Wi-Fi or Ethernet) or USB serial. DCC-EX is also compatible with JMRI and WiThrottle (both auto-detected on port 2560). See the DCC-EX page for the current ModelRailPro connection status.
Guide price: DIY build approx. €25–60; RTR kit approx. €80–150 (indicative). No factory warranty; support via the DCC-EX community (dcc-ex.com).
Both command stations are compatible with ModelRailPro. The choice is not about the software but about your hardware requirements. Considering Märklin locos as well? Read Z21 vs Märklin CS3.
ModelRailPro