Important

This utility will only work with an AMD GPU!

If you're using an Nvidia GPU, see this project for using NVapi.

If you're using Intel, you could watch this issue to see if someone writes a utility.

Warning

This utility sends data over the i2c bus. Use at your own risk.

Description

A simple CLI utility to issue the switch input command via DDC to a monitor connected to an AMD GPU.

Supports the --i2c-subcommand argument that's missing from alternative Windows DDC utilities, which enables issues input switching on some LG monitors. Implementing this argument is the entire point of this project.

Building

Built using VS2022

I may upload the binary, if requested.

Usage

Usage: amdddc-windows [options] [command]
Options:
  --i2c-source-addr <addr>             Set the I2C source address (Default: 0x51; For LG DualUp, use 0x50, which will then use 0xF4 for the side channel command)
  --verbose, -v                        Enable verbose output
  --help, -h                           Print this help message
Commands:
  detect                               Print the available monitors and displays
  setvcp <monitor> <display> <input>   Set the VCP command (currently only input switching)
                                       <input> for LG DualUp: 0xD0 for DP1, 0xD1 for DP2/USB-C, 0x90 for HDMI, 0x91 for HDMI2

Example output from detect:

> .\amdddc-windows.exe detect
Adapter Index: 0 Adapter Name: AMD Radeon(TM) Graphics
Adapter Index: 1 Adapter Name: AMD Radeon(TM) Graphics
Adapter Index: 2 Adapter Name: AMD Radeon(TM) Graphics
Adapter Index: 3 Adapter Name: AMD Radeon(TM) Graphics
Adapter Index: 4 Adapter Name: AMD Radeon(TM) Graphics
Adapter Index: 5 Adapter Name: AMD Radeon RX 7900 XTX
        Display Index : 0 Display Name : LG SDQHD
Adapter Index: 6 Adapter Name: AMD Radeon RX 7900 XTX
        Display Index : 4 Display Name : LG SDQHD
Adapter Index: 7 Adapter Name: AMD Radeon RX 7900 XTX
        Display Index : 8 Display Name : LG TV SSCR2
Adapter Index: 8 Adapter Name: AMD Radeon RX 7900 XTX
Adapter Index: 9 Adapter Name: AMD Radeon RX 7900 XTX

Example command to change input 0 (LG SDQHD) on adapter 5 to the USB-C input:

> .\amdddc-windows.exe --i2c-source-addr 0x50 setvcp 5 0 0xD1

Credits

The ADL bits are based off the ADL sample here

Commands, channel ids, etc were all helpfully sourced from the ddcutil wiki

The DDC spec listed here was helpful in determing the i2cset command to issue.