2 Replies Latest reply on Oct 15, 2020 11:23 PM by MaMi_1205306

    PSoC5LP : USB peripheral with PSoC5LP that has stopped power supply from the host


      Dear Sirs and Madams,


      This is a continuation of what we have confirmed in the following communities in the past.


      PSoC5LP : USBFS component suspend operation


      In this application, when the power supply from the host is stopped

      PSoC5LP goes into Low power mode.

      At that time, there was a problem that Dp and Dm became indefinite because the pull-up effect on the host side disappeared.


      We were told about a countermeasure to pull up the Dp / Dm line when the 5V power supply from the host is stopped,

      but this countermeasure does not seem to be appropriate due to the USB specifications.


      Therefore, we are considering monitoring VBUS and switching the control.


      In the USB peripheral of PSoC5LP, there is a setting of VBUS Monitoring in the Advanced option.

      We are thinking of using this function to control it.


      So We have some questions.



      About the setting of Configuration Attributes of Device Descriptor in USB peripheral,

      Does PSoC5LP behave differently when Device Power is set to "Self Powered" and when it is set to "Bus Powered"?

      Will the content of the notification to the USB host only change?



      If We select IO pin internal to the component in the Advanced option and set VBUS to SIO compatible pin,

      what is the threshold voltage (the boundary between the voltage that becomes "1" and the voltage that becomes "0")?



      When connecting VBUS to a pin that does not support SIO, how much should the voltage dividing resistor be increased?

      Reference: According to the figure on Page 32 of USBFS_v3_0.pdf, the voltage is divided between 30kΩ and 60kΩ.

      Is it okay to use 10 times (300kΩ, 600kΩ) or 100 times (3MΩ, 6MΩ)?



      When you enable the VBUS Monitoring settings,

      If VBUS supply is stopped during USB sleep, interrupts from the Dp / Dm line must be ignored until VBUS supply is resumed.


      This behavior is not automatically realized by the USB module or the automatically generated program,

      do we need to program and realize it?