Duet Software Framework

Duet Software Framework (DSF) is the software stack that runs on a Linux single-board computer (SBC, typically a Raspberry Pi) attached to a Duet 3 mainboard. It replaces the firmware's own web server and SD-card handling with a richer .NET-based environment, while RepRapFirmware (RRF) keeps doing the real-time motion control on the Duet. The SBC and the Duet talk over a binary link, either SPI or USB.

This documentation describes how DSF is put together and how data flows through it. It complements the auto-generated API reference (see the DuetControlServer, DuetAPI, DuetAPIClient and DuetWebServer namespaces).

Articles

Components - the processes and libraries that make up DSF
Object model - the central machine-state data structure and how it is kept in sync
Inter-process communication - the DCS Unix socket, connection modes, and command set
G-code flow - how a G/M/T-code is parsed, processed, and executed
Firmware link - the binary protocol (SPI or USB) and firmware-initiated requests
File management - the virtual SD card, path mapping, jobs, macros, file info
REST API - the HTTP endpoints exposed by DuetWebServer
Plugins - the plugin model, the plugin service, and the permission system
Building from source - prerequisites and deploying a build to an SBC

High-level architecture

flowchart TB
    subgraph clients["Clients"]
        DWC["DuetWebControl (browser)"]
        PANELDUE["PanelDue / serial"]
        CLITOOLS["CLI tools<br/>CodeConsole, CodeStream, ..."]
        EXTPLUGIN["Plugins (DuetAPIClient)"]
    end

    subgraph sbc["Linux SBC"]
        DWS["DuetWebServer<br/>(ASP.NET Core, HTTP/WS)"]
        DCS["DuetControlServer (DCS)<br/>heart of DSF"]
        DPS["DuetPluginService<br/>(root + non-root)"]
        PLUGINPROC["Plugin processes"]
    end

    DUET["Duet 3 mainboard<br/>RepRapFirmware"]

    DWC -->|HTTP / WebSocket| DWS
    CLITOOLS -->|IPC socket| DCS
    EXTPLUGIN -->|IPC socket| DCS
    DWS -->|IPC socket<br/>DuetAPIClient| DCS
    PANELDUE -->|UART| DCS
    DCS <-->|IPC socket| DPS
    DPS --> PLUGINPROC
    PLUGINPROC -->|IPC socket| DCS
    DCS <-->|SPI or USB| DUET

What each piece does

DuetControlServer (DCS) is the heart of DSF. It owns the object model, runs the G-code pipeline, maps virtual SD paths to the Linux filesystem (file management), exposes the IPC socket for every other process, and drives the Firmware link to RRF.
DuetWebServer (DWS) is an ASP.NET Core app that serves the DuetWebControl single-page app and the HTTP REST API. It does not talk to the Duet directly - it proxies everything to DCS over the IPC socket using DuetAPIClient. See IPC and Components.
DuetPluginService (DPS) installs, starts, stops, and sandboxes plugins. It runs as two instances (root and non-root) so that ordinary plugins never run with elevated privileges.
RepRapFirmware (RRF) runs on the Duet and performs motion planning and real-time control. DCS forwards to RRF every code it does not handle itself, and RRF asks DCS for macros, file I/O, and SBC-side code execution over the same link.

How the components connect

From	To	Transport
Browser (DWC)	DuetWebServer	HTTP + WebSocket
DuetWebServer	DCS	IPC Unix socket (`DuetAPIClient`)
CLI tools, plugins	DCS	IPC Unix socket (`DuetAPIClient`)
PanelDue / serial	DCS	UART
DCS	DuetPluginService	IPC Unix socket
DCS	RepRapFirmware	SPI (master + GPIO `TfrRdy`) or USB serial

Where to start