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TPS65987D: Automatic Volume Reset to Mid-Level on USB Connection with Tablet

Conor
Guru 12185 points
Part Number: TPS65987D
Other Parts Discussed in Thread: PCM2900C, TPS65987

Tool/software:

Hello,

We are conducting a test using the TPS65987D in a system as shown in the attached diagram. The system connects to a commercially available tablet via a USB Type-C cable.


However, we are encountering an issue where the tablet's volume automatically resets to a mid-level whenever the connection is established. This behavior occurs under the following conditions:

  1. Physical connection/disconnection of the Type-C cable.
  2. Resetting the TPS65987D (PD controller), which triggers the USB reinitialization process.

Our objective is to keep the tablet's volume always set to maximum, but the automatic adjustment to mid-level volume is problematic for our application.

Based on our analysis, we suspect the following potential causes:

  1. Tablet Behavior:
    The tablet's operating system might be resetting the volume to a default mid-level upon detecting a USB Audio Class device (PCM2900C in this case).

  2. TPS65987D PD Reset:
    The TPS65987D might be triggering a reinitialization process during the PD reset, which in turn causes the tablet to reset the volume.

  3. USB2046I Behavior:
    The USB hub IC might be contributing to the reinitialization sequence, leading to the volume reset.

We would like to confirm:

  1. Are there any recommended configurations or settings for the TPS65987D to minimize or prevent the volume reset during PD reset?
  2. Could the PCM2900C or USB2046I ICs be contributing to this issue, and if so, are there specific configurations we should review?
  3. Have there been similar reports of this behavior when using the TPS65987D in conjunction with USB Audio Class devices?

Additionally, if there are alternative methods to maintain a constant maximum volume (e.g., firmware modifications, GPIO configurations, or external hardware control), we would appreciate any recommendations.

Please let us know if further details or logs are required.

Thanks,

Conor

  • 0
    TI__Mastermind 37855 points

    Hi Conor,

    I am one of the engineers that supports the USB-C PD products at TI. I can provide some feedback about the USB-C PD portion, but not too much on the USB2046 or PCM2900C.

    From the PD perspective, the TPS65987D should not have a direct role in controlling volume level, so I am not sure what is causing this here. What we do control is the USB-C port connection and negotiation of contracts related to the USB-C PD protocol.

    Conor said:
    Physical connection/disconnection of the Type-C cable.

    Upon connection and disconnection, the TPS65987 will primarily be involved in negotiating a power contract and determining the connection Power(Source/Sink) and Data roles (DFP/UFP).

    Conor said:
    Resetting the TPS65987D (PD controller), which triggers the USB reinitialization process.
    Conor said:
    Are there any recommended configurations or settings for the TPS65987D to minimize or prevent the volume reset during PD reset?

    If you reset the PD controller, it will likely disconnect and reconnect the USB contract. I do not know how this affects the volume, but cannot think of a way to prevent disconnection when the device is reset.

    Conor said:
    Have there been similar reports of this behavior when using the TPS65987D in conjunction with USB Audio Class devices?

    I have not seen reports of this behavior in the past.

    I am going to reassign this thread to the team supporting the audio parts to see if their engineers can provide feedback.

    Thanks and Regards,

    Chris

  • 0 in reply to Christopher Lim1
    TI__Mastermind 46645 points

    Hi Conor,

    My suspicion is your first suggestion, that the driver is doing this. The PCM2900C reacts to USB audio class requests and sets the volume accordingly to however the OS/Driver wants it to be set to. It should not be reverting back to mid-level volume. Some memory might be required. For example, Windows remembers the last volume state of a recognized audio device and will revert back to that level once it is connected/switched to.

    Best regards,
    Jeff McPherson