USBTMC, Can't get device capability and Can't clear buffers

[(대학원생) 문석호 (물리학과) via Tech-talk <tech-talk at aps.anl.gov>]

Hello, 

I try to make epics control system for dg812(Rf signal generator of RIGOL).
The dg812 supported usb commuincation but the protocol is usbtmc so I used drvAsynusbtmc module of asyn. 
However, I faced  some error like below. 

I did the test in centos7 enviroment and the version of asyn is 4-26 and the version of base is 3.14.12.5 .
I also did the test with rasberrypi3 enviroment with same asyn and base version but it shows same error message. 

'Can clear buffer ~' and 'Can't get device capabilities ~'

The most strange thing is about usb mount. When I plug in the usb cable and check the usb mount at /dev, I can check that the usb is succesfully mounted with name 'usbtmc0'. 
However, after I run epics and see the above error, the usb is diconnected so I can't see the 'usbtmc0' at /dev directory.

 That thing happens at centos 7 environment and also in rasberrypi enviroment. 
Can you give me some advice about this error?

Best Regards 

SeokHoMoon

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Intense Beam and Accelerator Laboratory
Department of Physics

Ulsan National Institute of Science and Technology (UNIST)

50, UNIST-gil, Ulsan 44919, Republic of Korea

E-mail : msh3069 at unist.ac.kr, msh3069 at naver.com

Phone: +82-10-2767-9398

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