Can't open an USBTMC device which has a serial number with zero length.

vDorst commented 3 years ago

I have a cheap Siglent Technologies SDG1032X clone aka ALP1005

But pyvisa connect string looks like USB0::62701::60986::::0::INSTR

Python code and backtrace.

Python 3.8.5 (default, Aug 12 2020, 00:00:00)
[GCC 10.2.1 20200723 (Red Hat 10.2.1-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyvisa
>>> rm = pyvisa.ResourceManager()
>>> rm.list_resources()
('ASRL/dev/ttyS0::INSTR', 'ASRL/dev/ttyUSB1::INSTR', 'USB0::62701::60986::::0::INSTR')
>>> inst = rm.open_resource('USB0::62701::60986::::0::INSTR')
Traceback (most recent call last):
  File "/usr/local/lib64/python3.8/site-packages/pyvisa/rname.py", line 237, in from_string
    rn = subclass.from_parts(*parts)
  File "/usr/local/lib64/python3.8/site-packages/pyvisa/rname.py", line 315, in from_parts
    return cls(**kwargs)
  File "<string>", line 8, in __init__
  File "/usr/local/lib64/python3.8/site-packages/pyvisa/rname.py", line 173, in __post_init__
    raise TypeError(f.name + " is a required parameter")
TypeError: serial_number is a required parameter

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib64/python3.8/site-packages/pyvisa_py/highlevel.py", line 156, in open
    parsed = rname.parse_resource_name(resource_name)
  File "/usr/local/lib64/python3.8/site-packages/pyvisa/rname.py", line 241, in from_string
    raise InvalidResourceName.bad_syntax(
pyvisa.rname.InvalidResourceName: Could not parse 'USB0::62701::60986::::0::INSTR'. The syntax is 'USB[board]::manufacturer id::model code::serial number[::usb interface number][::INSTR]' (serial_number is a required parameter).

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib64/python3.8/site-packages/pyvisa/highlevel.py", line 3304, in open_resource
    res.open(access_mode, open_timeout)
  File "/usr/local/lib64/python3.8/site-packages/pyvisa/resources/resource.py", line 297, in open
    self.session, status = self._resource_manager.open_bare_resource(
  File "/usr/local/lib64/python3.8/site-packages/pyvisa/highlevel.py", line 3232, in open_bare_resource
    return self.visalib.open(self.session, resource_name, access_mode, open_timeout)
  File "/usr/local/lib64/python3.8/site-packages/pyvisa_py/highlevel.py", line 160, in open
    self.handle_return_value(None, StatusCode.error_invalid_resource_name),
  File "/usr/local/lib64/python3.8/site-packages/pyvisa/highlevel.py", line 251, in handle_return_value
    raise errors.VisaIOError(rv)
pyvisa.errors.VisaIOError: VI_ERROR_INV_RSRC_NAME (-1073807342): Invalid resource reference specified. Parsing error.

lsusb output:

Bus 005 Device 004: ID f4ed:ee3a Shenzhen Siglent Co., Ltd. SDG1010 Waveform Generator (TMC mode)
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0xf4ed Shenzhen Siglent Co., Ltd.
  idProduct          0xee3a SDG1010 Waveform Generator (TMC mode)
  bcdDevice            2.00
  iManufacturer           1 SIGLENT Technologies Co,. Ltd.
  iProduct                2
  iSerial                 3
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength       0x0027
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0
    bmAttributes         0xc0
      Self Powered
    MaxPower                2mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           3
      bInterfaceClass       254 Application Specific Interface
      bInterfaceSubClass      3 Test and Measurement
      bInterfaceProtocol      1 TMC
      iInterface              0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x84  EP 4 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0002  1x 2 bytes
        bInterval               1
Device Qualifier (for other device speed):
  bLength                10
  bDescriptorType         6
  bcdUSB               2.00
  bDeviceClass            0
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  bNumConfigurations      1
can't get debug descriptor: Resource temporarily unavailable
Device Status:     0x0001
  Self Powered

Instrument details

Model: cheap Siglent Technologies SDG1032X clone aka ALP1005
Communication: USB TMC modde
Link to the documentation (if available):

Output of `pyvisa-info`

Machine Details:
   Platform ID:    Linux-5.8.9-200.fc32.x86_64-x86_64-with-glibc2.2.5
   Processor:      x86_64

Python:
   Implementation: CPython
   Executable:     /usr/bin/python3
   Version:        3.8.5
   Compiler:       GCC 10.2.1 20200723 (Red Hat 10.2.1-1)
   Bits:           64bit
   Build:          Aug 12 2020 00:00:00 (#default)
   Unicode:        UCS4

PyVISA Version: 1.11.1

Backends:
   ivi:
      Version: 1.11.1 (bundled with PyVISA)
      Binary library: Not found
   py:
      Version: 0.5.1
      ASRL INSTR: Available via PySerial (3.4)
      USB INSTR: Available via PyUSB (1.1.0). Backend: libusb1
      USB RAW: Available via PyUSB (1.1.0). Backend: libusb1
      TCPIP INSTR: Available
      TCPIP SOCKET: Available
      GPIB INSTR:
         Please install linux-gpib (Linux) or gpib-ctypes (Windows, Linux) to use this resource type. Note that installing gpib-ctypes will give you access to a broader range of funcionality.
         No module named 'gpib'

I patched the code to make it work. Is is not an elegant solution but it works.

Modify usb.py:list_resources()
```
if len(serial) == 0:
serial = "N/A"
```

Modify usbtmc.py -> find_tmc_devices()

if serial_number == "N/A":
    serial_number = None

python script

import pyvisa
rm = pyvisa.ResourceManager()
l = rm.list_resources()
print(l)
inst = rm.open_resource(l[2])
print(inst.query("*IDN?"))

output

('ASRL/dev/ttyS0::INSTR', 'ASRL/dev/ttyUSB1::INSTR', 'USB0::62701::60986::N/A::0::INSTR')
*IDN SDG,1.01.01.27,02-00-00-21-24

MatthieuDartiailh commented 3 years ago

That's an odd one indeed. Ideally I would like to see how commercial VISA implementation handle the issue. Keysight offers VISA for Linux but only for specific kernel versions. Otherwise if you have access to a Windows machine you can go with whatever implementation you like. I would really like this data point because according to the VISA specification the serial number is a mandatory field of the address. Maybe we are just reading the serial wrong, your lsusb seem to think the serial number is 3.

vDorst commented 3 years ago

It is a cheap clone. Even info screen shows that the serial number has no value. So I think they forgot it to program it!

We also have a real SIGLENT Technologies function generator which works fine because it reports an serial number.

lsusb

Bus 005 Device 006: ID f4ed:ee3a Shenzhen Siglent Co., Ltd. SDG1010 Waveform Generator (TMC mode)
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0xf4ed Shenzhen Siglent Co., Ltd.
  idProduct          0xee3a SDG1010 Waveform Generator (TMC mode)
  bcdDevice            2.00
  iManufacturer           1 SIGLENT Technologies Co,. Ltd.
  iProduct                2 SDG1010
  iSerial                 3 SDG100E<snip; 5 numbers>
  bNumConfigurations      1

Resouce list: ('ASRL/dev/ttyS0::INSTR', 'ASRL/dev/ttyUSB1::INSTR', 'USB0::62701::60986::SDG100E<snip; 5 numbers>::0::INSTR') IDN request: *IDN SDG,SDG1010,SDG100E<snip; 5 numbers>,1.01.01.37R3,02-00-00-23-26

I there an other way to open a device just based on USBID? Otherwise I have to stick to older https://github.com/python-ivi/python-usbtmc library.\

In python-usbtmc I use it like this:

import usbtmc
instr =  usbtmc.Instrument(2391, 5973)

I was exploring your library because it is maintained. I also don't need the features of VISA. I currently send raw command already.

Sorry but I currently haven't the time to testing the Keysight VISA software in Windows.

It is fine to close this issue. I understand that you not going to chang the code for just one faulty device.

MatthieuDartiailh commented 3 years ago

The USBTMC norm requires the instrument to report a serial number. However RAW USB instrument that are technically supported only by NI can omit it. And NI VISA will report something similar to N/A but it does not appear to be normalized.

As a consequence I would likely accept a PR doing the following:

list such devices as RAW not INSTR using N/A
allowing to open them as RAW USB resources

However note that if you do not need any VISA functionality you could also consider simply using libusb directly. Sorry for the delay I started answering on my phone but lost the message and though I had commented.

pyvisa / pyvisa-py