VISA Read from USB returns strange data

[cordm]

Hi everyone,

I'm communicating with a custom USB device using the VISA interface. The device is directly attached to a USB port. There are two more devices of the same type connected to other USB ports. While investigating transmision errors, I dumped all the read traffic and found some really strange data. Some examples:

Something about Windows CIM functions

   T b ” ¤ ÿWUUõÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ„ € CIM_Process Abstract Locale UUID {8502C566-5FBB-11D2-AAC1-006008C78BC7} Caption @ ) 

A list of running processes

ô.ŽŠãÿÿ
 a(ŽŠãÿÿi  a(ŽŠãÿÿ `q7ŽŠãÿÿ
 a(ŽŠãÿÿi  a(ŽŠãÿÿ@ `Ñ”Šãÿÿ
`±.ŽŠãÿÿE `±.ŽŠãÿÿÀ Ùô¹& `±.ŽŠãÿÿ0 q捉ÿÿ
! \ W I N D O W S \ S Y S T E M 3 2 \ F O N T D R V H O S T . E X E Á0 `±.ŽŠãÿÿù# °Êl‹Šãÿÿ
0—6Šãÿÿ 0—6Šãÿÿ‘

Documentation about python threading maybe:

If after the decrement it is zero, reset the lock to unlocked (not owned
by any thread), and if any other threads are blocked waiting for the
lock to become unlocked, allow exactly one of them to proceed. If after
the decrement the recursion level is still nonzero, the lock remains
locked and owned by the calling thread.

A list containing mui files

ðìK ÀàÚ%äØ
 € " < m p u x a g e n t . d l l . m u i ».c ¤.c ¤.c h

Each example is accompanied by similar entries (e.g. more python threading documentation....). The traffic from the other devices contained nothing like this, just the expected traffic with the device.

So my question is: what the hell? I thought I would only encounter messages from my device. What is causing this traffic and how can I prevent it?

[rolfk]

Something is very hosed with that VISA driver installation. Instead of handing you data from the port it hands you data from anywhere in the memory of your system. Potentially even outside of the current process. I would delete that driver and reinstall it.