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[C5535] DEVCTL register

Kaka
Guru 24520 points

Hi community member,

Please let me confirm the following questions which they are related to USB function.

[Question.1]
According to TRM, the DEVCTL is explained as below.
******
1h = Above Session End, below AValid. 2h = Above AValid, below VBusValid. 3h = Above VBusValid.
******
In my understanding, the voltage for each values are below.
1h: 0V to 2.0V
2h:2.0V to 4.4V
3h: over 4.4V
Is my understanding correct? If no, please teach me the correct values.

[Question.2]
Would you please explain the detail for the status of "1h" and "2h" on VBUS bits in DRVCTL?

If you have any questions, please let me know.
Best regards.
Kaka

  • 0
    TI__Genius 12575 points

    Hi Kaka-san,

    In my understanding the voltage for each values will be :

    1h: 0V to < 0.2V
    2h: 0.2V to 4.4V /4.75V
    3h: over 4.4V / 4.75V

    Where 4.4V is for low powered USB device and 4.75V is for high powered USB device.

    But I will confirm this to you again after discussing with USB experts here.

    Regards

     Vasanth

  • 0 in reply to Vasantha K
    Guru 24520 points
    Hi Vasanth,
    Thank you for your response.
    Would you please explain the detail for your comments as below.
    >Where 4.4V is for low powered USB device and 4.75V is for high powered USB device.

    What is "low powered USB" and "high powered USB"?

    And I am waiting for your response after discussing with USB experts. And please provide the detail information of "1h" and "2h" on VBUS bits in DEVCTL.

    Best regards.
    Kaka
  • 0 in reply to Kaka
    Guru 24520 points

    Hi Vasanth,

    I heard the following information from your Engineer in the past.

    Bit Value Description  Voltage Level
    0x00b  Below Session End Between 0.2V and 0.8V
    0x01b Above Session End, below AValid 0.8 to 2V
    0x10b Above Avalid, below VbusValid  2V to 4.4V
    0x11b Above VbusValid  4.4V

    Would you please double check the voltage level on VBUS bits?

    Best regards.

    Kaka


     
      
     
     

  • 0 in reply to Kaka
    TI__Genius 12575 points

    Hi Kaka-San

    The data I provided was based on my tests and understanding.

    I need to confirm this with USB experts on this topic.

    I will get back to you on this.

    Regards

    Vasanth

  • 0 in reply to Vasantha K
    Guru 24520 points
    Hi Vasanth,

    Thank you for your comments.
    I am waiting for your response after discussing with USB experts.
    And please provide the detail information of "1h" and "2h" on VBUS bits in DEVCTL.

    Best regards.
    Kaka
  • 0 in reply to Kaka
    TI__Genius 12575 points

    Hi Kaka-san,

    Here are further updates  on VBUSVALID status bits.

    The USB On-The-Go specification defines a series of thresholds:

    · VBus Valid (required to be greater than 4.4 and 4.75VV)

    · Session Valid for ‘A’ device (required to be between 0.8V and 2.1V)

    · Session End (required to be between 0.2V and 0.8V)

    As mentioned above VBUS valid status holds good for OTG supported device. Since C5535 do not support OTG this wouldn’t be a valid status information. Only 2’b11 (above VBUSVALID) VBUS status might be valid to check after successful enumeration.

    Further in C5535 Datasheet section – 5.7.16, The USB2.0 peripheral on this device, does not support:

    • Host Mode (Peripheral and Device Modes supported only)

    • On-Chip Charge Pump

    • On-the-Go (OTG) Mode

    Also with respect to your question related to low power & high power device. This is categorized based on the current drawn on the VBUS. For further details suggest you to refer to section 7.2.1 in USB 2.0 specification.

    Hope this clarifies.

    Regards

    Vasanth