Osoyoo 3.5″ HDMI Screen – DDC/CI Function Guide

Product: Osoyoo 3.5″ HDMI Touchscreen Display

Feature: DDC/CI Communication Support

Standard: MCCS Version 2.2

Compatible OS: Windows, Linux, Raspberry Pi OS

What is DDC/CI? HDMI35 Display supports DDC/CI communication, and users can adjust various parameters of the display via HDMI I2C (DDC Channel) port.

Table of Contents

1Specification

DDC/CI Standard

Monitor Command and Control Set (MCCS) Version 2.2

Supported Commands

Code Description
0x03 Set VCP Feature
0x01 Get VCP Feature
0xF3 Capabilities Request
0x0C Save current settings

VCP Features

Code Function Access
0x04 Restore factory defaults WriteOnly
0x10 Adjust Brightness ReadWrite
0x12 Adjust Contrast ReadWrite
0x16 Adjust Red Gain ReadWrite
0x18 Adjust Green Gain ReadWrite
0x1A Adjust Blue Gain ReadWrite
0xB6 Get Display type ReadOnly
0xD6 Set Power mode (Power On/Off) ReadWrite
0xDF Get VCP Version ReadOnly
0xE1, 0xE2, 0xE3 Custom features Custom

2System Requirements

  • Any kind of OS (Win7/10/11, Debian, Ubuntu, RaspberryOS…) which is capable drive HDMI port’s I2C bus.
  • DDC/CI control can be implemented using specific tool (like as ddcutil), or manual programming.
  • DDC/CI control is able when the display is in sleep/suspend mode, so can be used for power status control.

3Usage (ddcutil)

There are many of DDC/CI control apps, for example, ddcutil is very convenient and popular tool for Linux users.

For install, config, usage of ddcutil, please reference the documents:

Detect Display

ddcutil detect
ddcutil detect

Get Capabilities

ddcutil capabilities
ddcutil capabilities

Adjust Brightness

ddcutil setvcp 10 70    # Set brightness to 70 (range: 1~100)
ddcutil getvcp 10       # Get current brightness
Adjust brightness

Adjust Contrast

ddcutil setvcp 12 80    # Set contrast to 80 (range: 1~100)
ddcutil getvcp 12       # Get current contrast
Adjust contrast

Adjust Colors

Red:

ddcutil setvcp 16 128   # Set Red gain to 128 (range: 1~255)
ddcutil getvcp 16       # Get Red gain

Green:

ddcutil setvcp 18 128   # Set Green gain to 128 (range: 1~255)
ddcutil getvcp 18       # Get Green gain

Blue:

ddcutil setvcp 1A 128   # Set Blue gain to 128 (range: 1~255)
ddcutil getvcp 1A       # Get Blue gain
Adjust colors

Save Current Settings

ddcutil scs             # Save settings to EEPROM
Save current settings
Note: Modified contrast, color… values (except brightness) are not saved directly. This command stores the values to the display’s non-volatile storage.

Restore Factory Defaults

ddcutil setvcp 04 01    # Discard all changes, back to factory default
Restore factory defaults
Note: This command is ignored if the value is 00.

Power Status Control

ddcutil setvcp D6 01    # Power ON display
ddcutil setvcp D6 03    # Power OFF / Suspend display
ddcutil getvcp D6       # Get current power status
Power status control
Value Status
01 Normal status
02 Standby status (when no input signal, readonly value)
03 Suspend status (minimum power consumption)

Custom Commands

# Logo Control (E1)
ddcutil setvcp E1 1     # Enable logo (default: 1)
ddcutil setvcp E1 0     # Disable logo

# HDMI Note Control (E2)
ddcutil setvcp E2 1     # Enable HDMI note (default: 1)
ddcutil setvcp E2 0     # Disable HDMI note

# Sleep Control (E3)
ddcutil setvcp E3 1     # Enable sleep when no signal (default: 0)
ddcutil setvcp E3 0     # Disable sleep, always shows

For more detailed data transaction protocols, packet structures, please reference: https://www.ddcutil.com/bibliography/

4DDC/CI – Raspberry Pi Issues

Important: HDMI port’s I2C bus is enabled by default in latest RaspberryPi OS KMS driver mode. For using the I2C in FKMS driver mode, it needs extra configuration.

For FKMS mode, you need to add the following to config.txt:

dtparam=i2c2_iknowwhatimdoing
Known Issues:

  • It does not work in Raspberry Pi 4, Bullseye, 64bit… and KMS mode is almost essential for running DDC/CI applications.
  • The specific, non-standard resolutions (like as 480×320) require FKMS mode, so DDC-CI control is unavailable when using 480×320 resolution in many cases.

5Windows Tools

Recommended DDC/CI tools for Windows:

Windows Tools
Developer Note: There are also many of C, Python… DDC/CI libraries, resources, and users can develop customized DDC/CI display control app using appropriate libraries.

6Tech Support

Need help or have feedback? Submit a ticket and our team will get back to you within 1-2 working days.

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