FX2LP Selective Suspend - KBA222441

Version: **

 

Question:

Why does FX2LP not enter the suspend mode even when there is no activity on the data lines?

 

Answer:

Any USB device enters the suspend mode when there is no activity on the USB data lines for a period of 3 ms. In case of FX2LP, this happens when the power policy is set by the cyusb3.sys driver. For the driver to enable this power policy, the device’s configuration descriptor must make sure that the remote wakeup bit is set. Also, with some of the older host controller drivers, the selective suspend feature is not enabled. This will prevent the device from entering the suspend mode because of the SOF packets sent on the USB bus. The selective suspend feature works well with 3.0 host controllers.

 

To obtain the latest drivers for FX2LP, install the FX3 SDK from the below link.

http://www.cypress.com/documentation/software-and-drivers/ez-usb-fx3-software-development-kit

 

After installing SDK, you can find the driver in the default location: C:\Program Files (x86)\Cypress\EZ-USB FX3 SDK\1.3\driver\bin