How to reset my CP2103 device on PC through USB instead of unplugging.

(I am running VCP driver on PC.)

Therefore, to reset the CP210x from PC, you have to send a command to the MCU over the CP210x!! It isn't practical, considering the situation in which reset is required.

For the communication problem, USB bus reset will re-initialize the USB side of the chip.

To issue USB bus reset on the PC,

a) Device Manager (manually)
On the Device Manager, the CP210x is enabled/disabled using "device usage" pull-down on "general" property. When disabled once, and enabled again, USB bus reset is issued to the chip.

CP210x VCP port is found under "Port (COM and LPT)" tree.

b) DevCon (DOS command)
Above manual procedure is done using DevCon command on DOS window

> devcon disable @"USB\VID_10C4&PID_EA60\0001"
> devcon enable @"USB\VID_10C4&PID_EA60\0001"

Where, 0001 is the serial number of the chip

These commands are executed using ShellExecute( open ) from your code.

Also, you can extract the procedure from the source code of DevCon.
DevCon source is included in WinDDK.

C:\WINDDK\3790.1830\src\setup\devcon\

[References]

DevCon
http://support.microsoft.com/kb/311272/en-us

"Commands for DevCon Operations" on MSDN
http://msdn2.microsoft.com/en-us/library/ms792835.aspx

"ShellExecute Function"
http://msdn2.microsoft.com/en-us/library/bb762153.aspx

WinDDK
Free WinDDK (Server 2k3 SP1 DDK) is downloaded from MS
"DDK - Windows Driver Development Kit" from MS WHDC
Find "Download the Windows Server 2003 SP1 DDK [236 MB ISO file]" link

Burn the ISO image file into a CD-R disk after download.

Some hubs (or root hubs) support this function, but others not. Then, it isn't a certain way.

Related spec is here.
11.11 Hub Port Power Control (usb_20.pdf p334)

And related topic on USB-IF.
"switching off the USB power supply"
http://www.usb.org/phpbb/viewtopic.php?t=12754

Tsuneo