Issue with I²C Access Sample Code on External Monitor via Type-C Connection (0x6E 0x80 0xBE Response

[Niki28]

Dear Intel Support Team,

I am writing to report an issue I encountered when using the I²C access sample code available on your GitLab repository. Specifically, I am running the sample on my ThinkBook 16p Gen4 laptop (13th Gen Intel Core i9-13900, Windows 11), connected to an external monitor using a Type-C cable.

Below are the details of the issue and the steps I followed:

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Issue Summary:

• Problem:
  The I²C Read operation returns the following data consistently:
  0x6E 0x80 0xBE

• Expected Behavior:
  According to the provided code, the response should contain the correct brightness value (usually at the 10th byte) after performing a write operation and then a read from address 0x6E, subaddress 0x51.

• Steps I Followed:

  1. I connected the external monitor via Type-C Alt Mode.
  2. I ran the provided sample code without modification on Windows 11.
  3. The write operation executes without any reported errors.
  4. However, the read operation returns 0x6E 0x80 0xBE, which seems to indicate an invalid response or an unsupported command.

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Additional Details:

1. Setup Information:

   • Laptop: ThinkBook 16p Gen4
   • CPU: 13th Gen Intel Core i9-13900
   • OS: Windows 11
   • Connection: Type-C cable to an external monitor (Type-C Alt Mode)

2. Suspected Causes:

   • The external monitor may not fully support the MCCS VCP command set over the I²C channel.
   • There could be compatibility issues with the Type-C Alt Mode or the sample code’s I²C write/read sequence.
   • It is also possible that 0x80 in the response indicates that the operation is not supported by the connected monitor.

3. Requested Assistance:

   • Could you please confirm if 0x6E 0x80 0xBE indicates a specific issue, such as unsupported VCP commands or communication issues over the Type-C Alt Mode connection?
   • Are there any modifications required to the sample code to support external monitors connected via Type-C?
   • If there are known limitations or alternative approaches, could you provide guidance on the correct way to query the brightness or other display parameters?

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Thank you for your time and assistance in resolving this issue. Please let me know if you require any further information or logs.

Best regards,
Niki