Who powers the UART on VC707?

[betontalpfa]

I have problems with UART on VC707 devboard with Windows7.

Who powers the serial/USB bridge(U44)? I plugged the UART's USB to PC, but the board (VC707 itself) was un-powered. The serial port was invisible (from device manager). Then I powered-up the board (switch on the red switch on VC707), and the serial port was listed in COM ports even after if I switched the board off (but the USB was still connected). What is the base of the phenomenon? Should I power first? How can I debug power on behavior properly?

[drjohnsmith]

Your experiencing a few things here,

One is your OS, I'm guessing windows, and the usb drivers ,

    the other is the chip on the board

Re the board, 

   Which of the USB ports are you plugged into

Assuming I have the right board

https://www.xilinx.com/support/documentation/boards_and_kits/vc707/ug885_VC707_Eval_Bd.pdf

look at page 9 and 10.

Assuming your on the U44 usb to uart bridge, a Silicon labs CP2103GM

Page 42 says the chip is powered off the Host PC.

So it comes up as soon as the PC is plugged into the USB 

   But the OS can take quiet a time  to see it ,

          especially the first time, the pc might have to download / install drivers.

In essence, don't worry about it 

[betontalpfa]

I have updated my post regarding your assumptions.
But the serial port becomes visible always (exactly) when I power-up the VC707 board (with the red switch.)

If I simply plug the USB the COM port wont came up even if I wait an hour.

But then if I switch off the VC707 (but the USB is still plugged in) the COM port remain visible, and the terminal remain connected. But Is it safe?

[drjohnsmith]

yes. for a dev board its safe