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TUSB8040A / function of USB hub

Guru 29690 points
Other Parts Discussed in Thread: TUSB8040A
Hi Team,
 
I'd like to ask about TUSB8040A.
My customer is having troubled in his PC system using TUSB8040A under cirtain condition.
When he connects FS device(keyboard) to TUSB8040A on downstream port, he occasionally found USB+ signal stick "L" level for 12ms, then it repeats at 5 seconds interval and never to end. 
*The USB+(attatched) is the signal between TUSB8040A and FS device.
 
 
This behavior isn't expected function for him, and I was asked if this issue could be considered as Bus Reset from USB hub(TUSB8040A). 
He is also suspicious of upstream port transaction, however he would like to know this first.
 
Could you give me your comment please?
Your help would be appreciated.
 
Best regards,
Yaita 
  • Hello Yaita,

    What is happening on the system / keyboard when this occurs?  A hub is a slave device controlled by the USB host, so it will not create bus conditions unless the USB host initiates them.

    Regards,

    JMMN

  • Hi JMMN-san,
     
    Thank you for your support.
    I heard continuous character input had occured in his system.
     
    I will get more information from my customer.
     
    Best Regards,
    Yaita 
  • Hi JMMN-san,
     
    I heard from my customer that Keyboard(FS) device had some sort of bug and modifying made the function normally.
    The issue isn't related to TUSB8040A.
     
    Thank you for your support.
     
    Best Regards,
    Yaita