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libsig

What is libsig

libsig is the code. The product the project is aiming at is a lightweight IoT platform: the aim is that you build libsig onto your devices and run cloud instances that process the signal data those devices produce.

Today, a capsule is a unit of logic with named input and output terminals that runs inside a service in the host. It is the small unit a system is assembled from. The aim is that a capsule is a piece of code meant to run on a device or in the cloud; that placement is not built yet (see Roadmap).

The rest of this page separates that aim from what you can use today.

Today

Section titled “Today”

libsig is a C11 framework for POSIX platforms (Linux and macOS only). It provides:

  • capsules with named input and output terminals;
  • services, each with its own worker thread, that deliver signals between capsule instances;
  • projects: a directory of JSON files that defines capsule configurations and wires them into services;
  • sighost, a host program that loads a project and runs it;
  • a management API (a C interface and a REST transport over HTTP), a WebSocket signal feed, and a standalone web UI that edits a running project;
  • built-in capsules: counter, simulator, logger, filter, switch and state_change, plus weather, which needs the optional HTTP client.

Today capsules run in the host process you start on a POSIX machine. Running them on devices or in the cloud is planned: see the Roadmap.

Roadmap

Section titled “Roadmap”
  • Microcontroller targets, for example an Arduino reading a GPIO pin.
  • Secure channels between deployments over TCP, MQTT or ZMQ.
  • Cloud instances that subscribe to device data.

Nothing in the documentation describes these as available. They appear here and in the home page roadmap only.

Vocabulary

Section titled “Vocabulary”
Term Meaning
Capsule Compiled-in code with named input and output terminals and a table of properties it accepts.
Terminal A named input (with a handler) or output of a capsule. A signal emitted on an output terminal is delivered to the input terminals it is connected to.
Configuration A named, configured capsule, stored as configurations/<Name>.cfg.
Service A worker thread with a signal queue that owns a set of capsule instances and delivers signals between them. Stored as services/<name>.cfg.
Instance One configuration as used by one service, with its own state. This is what runs.
Project A directory of configuration and service files, loaded and wired together.

Architecture covers these in detail, including lifecycle, ownership and threading rules. Configuration describes the file formats.

Where to go next

Section titled “Where to go next”