sorry for the delay in reply

>Could you verify that the HidSmbus_Close hasn't been called twice by accident?
HidSmbus_Close is called only once

only source code

https://cloud.mail.ru/public/uhdF/XdCnrf1td

full project

https://cloud.mail.ru/public/pqjC/FPSRyb9Lp

screenshort

i created custom application for use CP2112 in MSVC2017 15.7.1 ( adding SLABHIDDevice.dll SLABHIDDevice.h SLABHIDtoSMBus.dll SLABHIDtoSMBus.lib )

sometimes there is such behavior that nothing happens on the I2Cbus
but HidSmbus_Open return HID_SMBUS_SUCCESS ( and all other commands )
In the VisualStudio in the window Output writes CHIDDevice::Close(): device not open on function HidSmbus_Close

what could have happened and how to fix it ?

Full command sequence

HidSmbus_GetNumDevices return HID_SMBUS_SUCCESS dwNumDevices=1
HidSmbus_Open return HID_SMBUS_SUCCESS
HidSmbus_GetSmbusConfig return HID_SMBUS_SUCCESS bitRate=40000 ackAddress=2 autoRespond=1 writeTimeout=100 readTimeout=100 sclLowTimeout=0 transferRetries=1
HidSmbus_SetSmbusConfig return HID_SMBUS_SUCCESS bitRate=40000 ackAddress=2 autoRespond=1 writeTimeout=100 readTimeout=100 sclLowTimeout=0 transferRetries=1
HidSmbus_SetTimeouts return HID_SMBUS_SUCCESS
HidSmbus_CancelIo return HID_SMBUS_SUCCESS
HidSmbus_GetUsbConfig return HID_SMBUS_SUCCESS vid=10C4 pid=EA90 power=50mA powerMode=0 releaseVersion=100

HidSmbus_WriteRequest return HID_SMBUS_SUCCESS
HidSmbus_TransferStatusRequest return HID_SMBUS_SUCCESS
HidSmbus_GetTransferStatusResponse return HID_SMBUS_SUCCESS status0=1 status1=1 numRetries=0 bytesRead=0

HidSmbus_Close return HID_SMBUS_SUCCESS <--  VisualStudio in the window Output writes CHIDDevice::Close(): device not open

Hi all
I disabled the antivirus and installed the program "install-studio-v4_x64". 
But I also can't find the file flash8051.exe. 
There is only a folder "python". 
Search in all files also did not find flash8051.exe

read about this file in this article

https://www.silabs.com/community/mcu/8-bit/knowledge-base.entry.html/2017/08/02/does_simplicity_comm-MyMc