Cmod S7 - Using USB Serial while externally powered with VU pin

[KMS]

Hello,

I need to be able to use the USB serial/JTAG interface while the Cmod S7 is powered externally using the VU pin. The datasheet says "To avoid risk of damage, any power source attached to the VU pin must be disconnected before a USB host is attached." This is a problem if you want to communicate with the module via USB while installed in a carrier card.

The USB circuit is missing from the schematic. Can diode D17 be removed to prevent the board from being powered via USB? If so, will the USB circuit still function? If not, what is Digilent's recommendations on using the USB port while the Cmod S7 is powered externally?

Thanks,

Kevin

[JColvin]

Hi @KMS,

Yes you can remove the D17 in order to power the board externally and still have the FTDI chip remained powered (though the USB circuitry will suspend when there is no connection to a host computer.

This is discussed in more detail in this thread here for the Cmod A7 (which has the same style of layout as the Cmod S7). https://forum.digilent.com/topic/17336-cmod-a7-datasheet-warning/#comment-55475

 

Thanks,
JColvin