bicarlsen / easy-scpi Goto Github PK

Greetings Brian,

Couldn't find how to get in touch (linked-in won't let me, twitter account from there is down) so am using this. Not writing about an issue, just some thanks.

I've been using easy-scpi to build wrappers from the devices I have and use the most and it made everything extremely easy.

I made some classes to give the objects derived from scpi.Instrument utility functions (and autocomplete!) so I don't have to remember each thing's API. I've been using this stuff for a while, but as I was doing a demo of it on a recent livestream I decided it might be useful to others.

If you're curious how I'm using the lib, its the Rigol DSO, Unitrend signal generator and Siglent power supply support in: https://github.com/psychogenic/psytestbench

In any case, thanks again.
Cheers,
Pat D

Dear Brian,

I have a TCPIP instrument whose API includes some parametrized SCPI queries in the form of :STUFf:THINg?[<wsp>MIN|MAX|DEF|SET|ACT|ALL] and I can't find how to perform those queries using easy_scpi.

Trying:

my_instrument.stuff.thing('MIN')

would return a fixed int (let's say 24 for instance). easy_scpi does no processing of the response so I believe this integer is genuinely sent back by the instrument although its documentation does not mention it.

Am I doing it wrong or is it not yet supported by easy_scpi?

Thank you for your time and your great abstraction work in this module.

Dear Brian,

I spent a few hours trying to figure out how to use easy-scpi for my use case and I thought you might be interested in my conclusions:

• My SCPI instrument has parametrized queries (see this previous issue) so I have to call the SCPI_Instrument.query() method which is not much different than using PyVISA directly.
• My instrument has several "channels" (let's say they are channels) of which I use only a subset. Making that subset user-defined at my instrument class instantiation (inheriting from SCPI_Instrument) does not mixes well with easy-scpi parsing of nested method calls of my instrument. This could be done using eval() although this generalization negates the ease-of-use of easy-scpi:

eval(f"my_instrument.{channel_label_as_a_string}.whatever()")

• It hides away PyVISA objects and makes manual control of my instrument MUCH MORE USER-FRIENDLY for testing and debugging.
• It is one more library in the final requirement file and I have to consider the licensing if I intend to redistribute my work.

Overall, I believe it's still worth interacting with my instrument as a subclass of SCPI_Instrument, mostly for the third point. The class methods are identical to an ab initio class based on PyVISA (assuming some aliases for the query() and write() methods of the PyVISA resource).
The fourth point will have to be considered of course.

Hi, I have a problem with sending commands over TCPIP using this lib.

Simple code:
inst = scpi.Instrument(port_match=False) inst.rid='TCPIP0::192.168.8.211::30000::SOCKET' inst.connect() print(inst.id())

TCPIP0::192.168.8.211::30000::SOCKET Traceback (most recent call last): return self.query( '*IDN?' ) raise errors.VisaIOError(rv) pyvisa.errors.VisaIOError: VI_ERROR_TMO (-1073807339): Timeout expired before operation completed.

What I observe is that even to use pyvisa manager I have to set termination sign. I tried in such way:

inst.__inst.read_termination = '\n'
inst.__inst.write_termination = '\n'

But it is not working this should be set in such way:
self.__inst = self.__rm.open_resource( self.rid, read_termination = '\n', write_termination = '\n')

Do you have any workaround or hint how to fix that without changing a code??

`pip list
Package Version

easy-scpi 0.1.4
modbus-tk 1.1.2
pip 21.2.3
pymodbus 3.0.2
pyserial 3.5
PyVISA 1.13.0
PyVISA-py 0.6.0
setuptools 57.4.0
typing_extensions 4.4.0`

Use case: Owon HDS200 series scope meter.

In this SCPI dialect, normal commands and queries usually(?) start with a mandatory ":".

Currently INSTRUMENT.chan.("OFF") sends CHAN OFF to the device. For the Owon to not ignore command, it must begin with a colon: i.e. :CHAN OFF to turn off the signal generator channel.

As expected, INSTRUMENT.:chan("OFF") and variants make Python throw errors, while easy-scpi already properly injects colons deeper in the hierarchy: INSTRUMENT.foo.bar(42) translates to <>FOO<:>BAR 42 (<> marks the spots).

So my issue is just a way to add the missing first colon on (some?) sent commands.

Possible implementation for this:

In the invoking script, permit the use of some horribly long "unique" string such as REPLACEBYCOLON as prefix to <SCPI-CLASS-NAME>.

Then mangle the used top class name of the command before sending by substituting REPLACEBYCOLON with just a colon. A global prefix on sending will probably have to implement exceptions, as e.g. the Owon dialect and esp. the programming guide are a bit - hmmm - funny.

Maybe make REPLACEBYCOLON configurable for the caller, thus that on collision or via eval the user can can change it or turn it off for a bit..

Thx,
Peter

Your example in the readme is confusing for beginners who don't know about VISA.
What should "<port>" look like in

# Connect to an instrument
inst = scpi.Instrument( <port> )

e.g I have a device I want to talk scpi comms to over tcp/ip on ip address 169.254.89.0 port 5025.

Trying these all fail:

inst = scpi.Instrument( "169.254.89.0:5025" , read_termination='\n', write_termination='\n')
inst = scpi.Instrument("169.254.89.0", read_termination='\n', write_termination='\n')
inst = scpi.Instrument("TCPIP0::169.254.89.0::5025::SOCKET", read_termination='\n', write_termination='\n')

What is a concrete example for the value ?

I eventually found that this worked:

inst = scpi.Instrument(read_termination='\n', write_termination='\n')
inst.rid="TCPIP0::169.254.89.0::5025::SOCKET"

Can you add an explanation to setting the rid in the readme if this is the correct connection method for tcp/ip case or explain the scpi.Instrument( <port> ) better.

Im using the pyvisa-py backend under Windows. When I try connect to an Instrument and set the backend to '@py' explicitly, I get the following error:

SerialException: could not open port 'COMCOM7': FileNotFoundError(2, 'The system cannot find the file specified.', None, 2)

If I don't set any backend it works flawlessly. I think removing the following if-clause would solve the problem:

I didn't open a pull request, because I wasn't sure if the if-clause is needed for something.

Looks like only COM and USB are supported, but PyVisa supports GPIB, so this should be a simple change?

Hi!

Thanks for this initiative. I'm trying to use this library to communicate with a SCPI-enabled device over a serial link, running in linux.

The serial device that it's connected to is /dev/ttyACM0 and the underlying port that should be passed on to pyvisa should be ASRL/dev/ttyACM0::INSTR.

To make this work, I need to initialize the instrument using

inst = scpi.Instrument("COM/dev/ttyACM0"), which is a bit awkward under linux as the "COM" terminology isn't used there.

I'm trying to enter a command to my SCPI-enabled device that takes multiple parameters:

Concretely"

MEMory:WORD <address>,<value>

With a concrete invocation of:

MEM:WORD #H0196, 511

However, when I try to execute inst.mem.word(0x196, 512), I get:

Traceback (most recent call last):
  File "easy_scpi_test.py", line 20, in <module>
    main()
  File "easy_scpi_test.py", line 13, in main
    inst.mem.word(0x196, 512)
TypeError: __call__() takes from 1 to 2 positional arguments but 3 were given