comedi

Comedi, short for Control and Measurement Device Interface, is an open-source software project that provides a common interface for data acquisition and measurement hardware on Linux. It combines kernel-level device drivers with a userspace library (libcomedi) to enable portable access to a wide range of data acquisition boards and devices.

Architecture and interface

The project offers kernel drivers that expose hardware as comedi devices. Each device can include multiple subdevices representing different I/O capabilities, such as analog input, analog output, digital I/O, counters, and timers. Userspace programs interact with the hardware through the /dev/comediN devices and the libcomedi library, which provides a high-level API for configuring devices, issuing commands, and transferring data. The API supports features such as scanning analog channels, buffering, and interrupt- or polling-based data transfer.

Hardware support

Comedi aims to support a broad spectrum of boards from various vendors, including PCI, USB, and plug-in modules. It acts as a unifying layer so that software can access many different devices through a common interface, facilitating data acquisition, instrumentation, and laboratory experiments without vendor-specific code.

Licensing and availability

The project is released under an open-source license (GPL) and has historically been distributed with several Linux distributions. Documentation, tutorials, and API references are available through the project’s resources, including man pages and online references.

Usage and context

Comedi has been used in research, education, and industry to acquire sensor data, control actuators, and manage measurement setups on Linux systems. While newer hardware may be supported by vendor-specific drivers or alternative frameworks, Comedi remains a foundational option for broad compatibility with legacy and some contemporary data acquisition hardware.

See also

Data acquisition, Linux device drivers, libcomedi.