DDCCI

DDCCI, short for Display Data Channel Command Interface, is a software-accessible protocol that enables two-way communication with computer monitors via the Display Data Channel (DDC). Built to run over the monitor’s I2C-based data channel, DDCCI allows a host computer to query monitor status and read EDID information, as well as issue control commands to adjust settings such as brightness, contrast, color temperature, and other image parameters.

DDCCI is commonly considered a practical realization or extension of the DDC/CI standard developed by VESA. DDC/CI provides a defined command set and data formats for two-way communication between a PC and a monitor, enabling software-based display control beyond what is available via the on-screen display (OSD).

Typical operation involves sending a command code (VCP code) with optional data to the monitor over the DDC channel; the monitor replies with a status value or a data payload. Common controls include brightness, contrast, red/green/blue color gains, and color temperature. Real-world implementations vary by vendor, and some monitors expose only a subset of commands or require enabling DDC/CI in the monitor's OSD.

Software implementations exist on multiple platforms, including Linux tools such as ddccontrol and ddcutil, Windows APIs and third‑party utilities, and some macOS applications. Many modern operating systems provide access to DDC/CI through driver libraries or hardware monitor chips, or through USB display adapters that bridge the I2C channel.

Limitations include inconsistent support across displays, possible vendor restrictions, and potential security implications since malware with sufficient privileges could alter display settings. When supported, DDCCI provides a convenient programmatic way to manage display parameters without relying on manufacturers’ proprietary software.