Hello,
I am trying to get an Agilent U2741A Digital Multimeter working with
multiple versions of the usbtmc driver without much luck. One thing in
paticular that I am noticing is the output of lsusb -v. A large number
of values that I would expect to be found that would allow the driver to
find the device are 'Defined at Interface Level', such a bDeviceClass,
bDeviceSubClass, bInterfaceClass, bInterfaceSubClass, and many others
(see full output at the end of this email).
The 'old' usbtmc driver from the Agilent website has a usb_device_id
structure that only specifies .bInterfaceClass and .bInterfaceSubclass;
I did hack this portion of the driver to use .idVendor and .idProduct
and managed to get it to a very basic level of 'working' where it would
recognize the device.
There is also a 'new' usbtmc driver that is included in the kernel
sources. It matches the device using
USB_INTERFACE_INFO(USB_CLASS_APP_SPEC, 3, 0) and
USB_INTERFACE_INFO(USB_CLASS_APP_SPEC, 3, 1). I also modified this
driver by setting vendor and productId to even match my device, but
still without any luck getting the device to work; after a couple of
reads from the device I would get timeout errors, or after writing all
reads would return a timeout error (which was the exact same behaviour
from the 'old' driver).
But my main question is, what does it mean when lsusb -v outputs that a
field is 'Defined at Interface Level'? Because it seems that if these
values are not able to be seen by the driver, the first step of matching
the driver to the device does not work without hacking up a match for
the exact device and vendor id.
As promised, here is the full output of lsusb -v for this device:
------------------------------------------------------------------------------
Bus 001 Device 056: ID 0957:4818 Agilent Technologies, Inc.
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x0957 Agilent Technologies, Inc.
idProduct 0x4818
bcdDevice 11.11
iManufacturer 1 Agilent- APIC
iProduct 2
iSerial 238
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 97
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xc0
Self Powered
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 4
bInterfaceClass 0 (Defined at Interface level)
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 1
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 1
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 1
bNumEndpoints 6
bInterfaceClass 0 (Defined at Interface level)
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 1
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 1
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0200 1x 512 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x83 EP 3 IN
bmAttributes 1
Transfer Type Isochronous
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 1
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x03 EP 3 OUT
bmAttributes 1
Transfer Type Isochronous
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 1
Device Qualifier (for other device speed):
bLength 10
bDescriptorType 6
bcdUSB 2.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
bNumConfigurations 1
Device Status: 0x0001
Self Powered
------------------------------------------------------------------------------
And, as another request for help, any advice on using the usbtmc driver
or getting Agilent products to work under Linux would be greatly
appreciated.
Thank You.
--
Burton Samograd
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