Understanding DDC CI in Monitor: Functionality and Usage Guide (2024)

DDC (Display Data Channel) is a dedicated interface designed to facilitate information exchange between the computer and the monitor.

Multiple versions of DDC exist, including DDC 1, DDC 2B, and DDC2A/B.

So, what is a DDC CI?

DDC 1 is designed to transfer data in only one direction, from the screen to the PC. It typically contains information pertaining to the screen itself and its various parameters. This encoding method was commonly used in older models and was quite prevalent until newer technologies emerged.

DDC 2B allows for two-way data transmission, allowing information to be exchanged between the monitor and the computer, as well as from the PC to the monitor. It differs from DDC 1 in that it includes an additional line of information transfer for one of the command systems (DID, ExtEDID, VDIF).

DDC 2A/B is similar to the previously mentioned format, but is based on a different interface and offers a faster data transfer rate.

There are multiple standards for data transfer, with the main ones being VGA and VESA DDC/CI. This article will focus on the latter format.

The Display Data Channel Command Interface (DDC/CI) utilizes this technology to generate and transmit data to the display while also receiving response data. The encoding and command set standards for DDC/CI are outlined in the MCCS technical documentation. Although the details of this documentation are not publicly available, there is a publicly accessible documentation called ACCESS.bus Specifications Version 3.0, which provides information on device compatibility, a list of commands, and the various capabilities and functions they can be utilized for.

What the DDC CI is for

The primary role of the DDC is to transmit information about the image parameters. This is important for troubleshooting the picture and adjusting the screen modes based on the connected computer. This functionality enables bidirectional communication, allowing control and troubleshooting of both the computer and the monitor simultaneously.

To enhance convenience during setup, there are several utilities available that enable control of the monitor through the information transfer channel.

One such program is ddccontrol, which offers users a range of essential features, including:

• The brightness and contrast can be adjusted. These settings are modified on the hardware level of the screen itself, by adjusting the backlight. The user also has the option to modify the color gamut.

Important! It is only possible to change the backlight brightness if the screen itself supports this feature.

• There is the option to switch between different modes on the screen, such as movie, game, user, text preset, and others.
• Language settings can be changed, including languages that are not available for the region.
• Buttons on the device can be locked, including the power button.
• The monitor can be remotely turned on and off.
• The image can be moved.

Additionally, this utility provides the user with numerous opportunities that were not mentioned in the manual or other documents, and it was not possible to enable them using the control buttons on the device. For instance, one of these opportunities includes the ability to enable the Japanese language in the settings, which is normally not available in the European region.

Important! To access all of these functions, it is essential for the user to ensure that the monitor is DDC/CI compatible.

How to configure DDC CI

To access all the features offered by DDC CI technology, users must use the ddccontrol utility and load the necessary module: modprobe i2c-dev.

Next, users should locate the connected monitors. Once found, a list of monitors along with their settings and functionality will be displayed.

Attention! Some device models may not be included in the utility’s database. In such cases, users will need to manually search for options in the registers.

Here is a compilation of fundamental function commands:

• To output a list of all possible commands for the monitor, if this device is in the database, use the command ddccprobe -e -d dev:/dev/i2c-2.
• To lock or unlock the menu, use the command ddcontrol -r 0xf -w 1 dev:/dev/i2c-2. Set -w 1 for menu lock and -w 0 for menu unlock.
• To set the menu language, use the command -r 0xC -w 0 dev:/dev/i2c-2. Use values from 0 to 9: 0 for Chinese, 1 for Japanese, 2 for English, and 9 for Russian.

Note: The manual monitor setup may not include a Chinese or Japanese language setting.

• To shift the image on any connection, not just VGA, use the command -r 0xE -w 55 dev:/dev/i2c-2.
• -r 0xd and c-w 2 dev:/dev/i2c-2 Configure the device for "internet" mode. Use -r 0xdc register to specify the message. Use -w command to choose a value ranging from 0 (user) to 5 (movie).

Differences of ddc ci in different operating systems

Screen management offers a multitude of applications, coming from the manufacturers themselves as well as third-party developers.

The ddccontrol utility is the most versatile solution for controlling devices, as it works on both Windows and Linux. It offers extensive functionality, even for devices that are not included in its database.

For Windows users, Samsung has developed the magic tune application, which allows for easy and intuitive control of screen settings. However, this program is limited to Samsung devices, which limits its functionality.

LG also provides a similar program called forteManager (exclusive to Windows), and NEC/Mitsubishi offers NaViSet, which is available for both Windows and MacOS X.