Experimental Physics and
Industrial Control System

Hi Florian,

You would need to write an asyn port driver that is specific to USBTMC.  USBTMC is basically like GPIB over USB.  This driver will be similar to the VXI-11 driver, which is basically GPIB over Ethernet. 

That driver would implement the asynOctet interface, just like the drvAsynSerialPort driver does.  That should not be difficult.  You need to implement the ioctl for special operations. 

The following is from this document:

http://www.home.agilent.com/upload/cmc_upload/All/usbtmc.html?&cc=US&lc=eng

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ioctl(2): Special operations

As show in the above examples, ioctl(2) is used for special operations (everything that goes beyond text-based communication). The second parameter to ioctl(2) is a request code which indicates what kind of special operation you want the driver to perform. Valid request codes are defined in usbtmc.h. They are:

USBTMC_IOCTL_GET_CAPABILITIES

This request is used to get information about the device's capabilities. In this case, the third parameter to ioctl(2) is a pointer to a structure of type struct usbtmc_dev_capabilities (defined in usbtmc.h). This structure is filled by ioctl. See usbtmc.h and the USBTMC specification for details.

USBTMC_IOCTL_INDICATOR_PULSE

This request asks the device to light its activity indicator for identification purposes. This is an optional capability and may not be available with your device. Inspect the device's capability values when in doubt. In this case, the third parameter to ioctl(2) is not used.

USBTMC_IOCTL_CLEAR

This request is used to clear the device's input and output buffers. It is roughly equivalent to a GPIB device clear. In this case, the third parameter to ioctl(2) is not used.

USBTMC_IOCTL_ABORT_BULK_OUT

This requests aborts the last USBTMC BULK OUT operation, i.e. the last write operation to the device's command buffer. It is used to recover from I/O errors that occur during a write operation. Note that you can instruct the driver to do the abort automatically if an I/O error occurs. See Reference: Attributes for details. In this case, the third parameter to ioctl(2) is not used.

…

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Mark

Hi,

we were able to improve the situation a little bit. It looks like the native usbtmc support is broken since kernel  2.6.28-11. We installed the driver from Agilent
on our Debian 3.2.46-1 x86_64 machine and now we have /dev/usbtmc0 which returns information about the connected devices and /dev/usbtmc1 ... usbtmc16. With the latter we can now repeatedly communicate
 using echo (for example 'echo *IDN?>/dev/usbtmc1') and cat with the device and we get meaningful results. However, using the serial driver from asyn does not work, I guess since it is not
a pure serial device but rather a normal file in the linux file system where you can write to and read from.

Is there any possibility to get this working with asyn or do we have to find a new solution?

Cheers,

Flo

> From the device name this is is a USBTMC device, not a serial port.   I've seen similar behavior in older linux kernels, you might have more luck

> updating to a more recent kernel.

> 

> Guy Jennings

> 

> On Aug 2, 2013, at 10:36 AM, Eric Norum <[email protected]> wrote:

> 

>> Since you can communicate with the unit using simple shell commands I'm inferring that the unit presents itself as a USB-connected serial port.   Standard StreamDevice + ASYN support should work fine.

>> 

>> On Aug 2, 2013, at 5:42 AM, "Drube, Hardy" <[email protected]> wrote:

>> 

>>> Dear all,

>>>  

>>> I have some problems to establish a longer lasting connection with a Thorlabs PM100USB Powermeter.

>>>  

>>> It is listed in /dev as usbtmc0 and I can communicate with it through echo –e. But this is only possible for one time. A second time echo –e won’t work. I have to disconnect and reconnect the USB-cable. Then again it will work one time.

>>> Could you help me with this problem?

>>>  

>>> Note: This device has two chips, the first one is a XILINX XCR3064XL (AD Converter) and the second a NXP LPC2387FBD100.

>>>  

>>> Best regards,

>>> Hardy Drube

>>> 

>> 

>> -- 

>> Eric Norum

>> [email protected]

>> 

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