USB low-full-high speed peripherals Forum Discussions

[JeBo_4132831]

Hi,

Another day, another question 🙂

I'm always on the same FX2LP18 board. Today, Firmware works in a Bus-Powered mode. 

I would like to add a Self-Powered capability to the firmware. The board is able to take the power either from the USB or from a Power Supply. I can monitor the USB_PWR through an I2C component by reading a register on it  (not directly using a PIN of the FX2LP18).

In Self-Powered Mode, What i need to do exactly onto firmware side, upon detection of USB_PWR ? 

Clear and set DISCON bit ?

Thanks.

Regards.

[PranavaYN · Accepted solution]

Hi,

Yes, you need to set DISCON if VBUS is not present and clear it when VBUS is present.

Please refer to Powering USB Devices section in the following appnote - https://www.cypress.com/documentation/application-notes/an15456-guide-successful-ez-usb-fx2lp-hardwa...

Here VBUS is monitored using a GPIO and DISCON bit is set/cleared accordingly.