Instrument Driver/Parameter Clarification

[pyquest1]

I have been trying to get QCodes parameter class to handle multi-type inputs. I.e. I am asking what is the right way to setup a parameter class to handle the following example.

Take the following example from a keysight frequency counter.

"""Configures the expected frequency CONFigure:FREQuency [{ | MINimum | MAXimum | DEFault} [,{ | MINimum | MAXimum | DEFault}]] [,]

    Channels 1 & 2:
        0.1 Hz to 350 MHz
        MIN = .1 Hz
        MAX = 350 MHz

        Example: self.counter.write('CONF:FREQ MIN') sets the expected frequency to 
        it's minimum'    
    """

So the right command in general would be something like

'CONF:FREQ ' + freq + ',' + resolution + ',' + '(@'+ str(channel) +')' .

However, this command has three value inputs, (freq,resolution,channel). The resolution and frequency can be both a float and a string like 'DEF'. I'm unclear based how to set up the set the parameter class to handle a setting this complicated from the documents.

Any help would be appreciated.

[Akshita07]

Hi @tmautry ,

What you are looking for, can best be done by implementing a class which inherits 'InstrumentChannel' class in qcodes. Then use 'add_parameter' with 'MultiType' validator to set min, max for your parameters. Lastly, you need to group your parameters with appropriate 'set_cmd' .

Following example might make things more clear for you.

    class MyChannel(InstrumentChannel):
        def __init__(self, parent, name, **kwargs):
            super().__init__(parent, name, **kwargs)

            self.channel_name = 'xyz'

            self.add_parameter(
                "frequency",
                vals=vals.MultiType(
                    vals.Numbers(0.1, 350),   # Hz
                    vals.Enum('MIN', 'MAX', 'DEF')),
                parameter_class=GroupParameter
            )
            self.add_parameter(
                "resolution",
                .....................
            )
            self.group = Group(
                [self.frequency, self.resolution],
                set_cmd=f'CONFigure:FREQ {{frequency}}, {{resolution}}, (@{self.channel_name})',
                ..........
            )

You can find more examples at following links:

https://github.com/QCoDeS/Qcodes/blob/master/qcodes/instrument_drivers/Keysight/private/Keysight_344xxA_submodules.py#L33

https://github.com/QCoDeS/Qcodes/blob/5a198290ed56bf1a81f53e7aa3744a6daf19e6d8/qcodes/instrument_drivers/Lakeshore/Model_372.py#L67

For more details on group_parameter, have a look at https://qcodes.github.io/Qcodes/api/parameters/group_parameter.html

I hope you can now solve the issue.

[pyquest1]

Hi Akshita07,

Thanks for the help. I am still struggling with this. Mostly this gives me an error that I can't track down/figure out why.

AttributeError: ("'NoneType' object has no attribute 'endswith'", 'asking None to ', 'getting Counter_1_frequency')

---

class Channel(InstrumentChannel): def init(self, parent, name, kwargs): super().init(parent, name, kwargs) self.visa_handle = self.parent.visa_handle

        self.channel_name = name

        self.add_parameter(
            "frequency",
            vals=vals.MultiType(
                vals.Numbers(0.1, 350*1E6),   # Hz
                vals.Enum('MIN', 'MAX', 'DEF')),
            parameter_class=GroupParameter)

        self.add_parameter(
            "resolution",vals=vals.MultiType(
                vals.Numbers(0.1, 350*1E6),   # Hz
                vals.Enum('MIN', 'MAX', 'DEF')),
            parameter_class=GroupParameter)

        self.config_freq = Group(
            [self.frequency, self.resolution],
            set_cmd= f'CONFigure:FREQ {{frequency}},{{resolution}},(@{self.channel_name})')

Then I run a set of commands to initiate the driver. The termination string is terminator=\n. I can then access this channel with the following command for instance:

key.Ch1.config_freq.set(1E5,'MAX')

---

But I get the following error:

File "", line 1, in key.Ch1.config_freq.set(1E5,'MAX')

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\utils\deprecate.py", line 59, in decorate_callable return func(*args, **kwargs)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 227, in set self._set_one_parameter_from_raw(set_parameter, raw_value)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 240, in _set_one_parameter_from_raw if any((p.get_latest() is None) for p in self.parameters.values()):

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 240, in if any((p.get_latest() is None) for p in self.parameters.values()):

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 2192, in call return self.cache()

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 2126, in call return self.get(get_if_invalid=True)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 2090, in get return self._parameter.get()

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 585, in get_wrapper raise e

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 572, in get_wrapper raw_value = get_function(*args, **kwargs)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 70, in get_raw self.group.update()

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 271, in update ret = self.get_parser(self.instrument.ask(self._get_cmd))

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\base.py", line 761, in ask raise e

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\base.py", line 754, in ask answer = self.ask_raw(cmd)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\visa.py", line 227, in ask_raw response = self.visa_handle.query(cmd)

File "C:\ProgramData\Anaconda3\lib\site-packages\pyvisa\resources\messagebased.py", line 607, in query self.write(message)

File "C:\ProgramData\Anaconda3\lib\site-packages\pyvisa\resources\messagebased.py", line 223, in write if message.endswith(term):

AttributeError: ("'NoneType' object has no attribute 'endswith'", 'asking None to ', 'getting Counter_1_frequency')

[Akshita07]

Hi @tmautry , you need to provide 'get_cmd' as well for the group. Currently, it is not provided in the code and hence the error. Also 'key.Ch1.config_freq.set(1E5,'MAX')' is not the correct usage as 'set' is a deprecated method on a group. Correct usage would be

channel.resolution.set('MAX')
channel.frequency.set('1e5')

In addition, self.visa_handle = self.parent.visa_handle in your code is unnecessary.

[pyquest1]

Hi @Akshita07. I appreciate the help...Unfortunately, there isn't a "get_cmd" for this command. The closest is a cmd 'CONF?' which returns the most recent setting, not necessarily the setting for the frequency and resolution. However, if the set cmd is run first then this get_cmd will work.

Even using CONF?, I get a strange error. This is why I want to set both parameters at the same tmie.

Here's the code (Note Counter is the name of the parent class that inherits VisaInstrument.)

---

    class Channel(InstrumentChannel):
            def __init__(self, parent, name, **kwargs):
                 super().__init__(parent, name, **kwargs)
                 self.visa_handle = self.parent.visa_handle

                 self.channel_name = name

        self.add_parameter(
            "frequency",
            vals=vals.MultiType(
                vals.Numbers(0.1, 350*1E6),   # Hz
                vals.Enum('MIN', 'MAX', 'DEF')),
            parameter_class=GroupParameter)

        self.add_parameter(
            "resolution",vals=vals.MultiType(
                vals.Numbers(1.0*1E-15,1.0*1E-5 ),   # Hz
                vals.Enum('MIN', 'MAX', 'DEF')),
            parameter_class=GroupParameter)

        self.config_freq = Group(
            [self.frequency, self.resolution],
            set_cmd= f'CONFigure:FREQ {{frequency}},{{resolution}},(@{self.channel_name})',
            get_cmd= 'CONF?')

---

key = Key53230A()   
key.Ch1.frequency(1E6) 

---

Traceback (most recent call last):

File "", line 1, in key.Ch1.frequency.set(1E6)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 638, in set_wrapper raise e

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 622, in set_wrapper set_function(raw_val_step, **kwargs)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 77, in set_raw self.group._set_one_parameter_from_raw(self, value)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 240, in _set_one_parameter_from_raw if any((p.get_latest() is None) for p in self.parameters.values()):

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 240, in if any((p.get_latest() is None) for p in self.parameters.values()):

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 2192, in call return self.cache()

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 2126, in call return self.get(get_if_invalid=True)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 2090, in get return self._parameter.get()

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 585, in get_wrapper raise e

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\parameter.py", line 572, in get_wrapper raw_value = get_function(*args, **kwargs)

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 70, in get_raw self.group.update()

File "C:\ProgramData\Anaconda3\lib\site-packages\qcodes\instrument\group_parameter.py", line 273, in update p.cache._set_from_raw_value(ret[name])

KeyError: ('resolution', 'getting Counter_1_resolution', 'setting Counter_1_frequency to 1000000.0')

[Akshita07]

Hi @tmautry ,

The error which you see now is because by giving get_cmd as CONF? you receive a string output which needs to be parsed. You can have a look at "53220A/53230A Frequency UniversalCounter/Timer Programmer’s Reference" for Keysight 53230A CONF? response format at https://www.keysight.com/main/techSupport.jspx?cc=US&lc=eng&nid=-33609.959903&pid=1893411&pageMode=OV Parsing can be done by writing a custom function based on CONF? response format and providing that to get_parser for the group. Example follows.

class Channel(InstrumentChannel):
    def __init__(self, parent, name, **kwargs):
        super().__init__(parent, name, **kwargs)

        self.channel_name = name

        self.add_parameter(
            "frequency",
            vals=vals.MultiType(
                vals.Numbers(0.1, 350*1E6),   # Hz
                vals.Enum('MIN', 'MAX', 'DEF')),
            parameter_class=GroupParameter
        )
        self.add_parameter(
            "resolution",
            vals=vals.MultiType(
                vals.Numbers(0.1, 350*1E6),   # Hz
                vals.Enum('MIN', 'MAX', 'DEF')),
            parameter_class=GroupParameter
        )
        self.config_freq = Group(
            [self.frequency, self.resolution],
            set_cmd= f'CONFigure:FREQ {{frequency}},{{resolution}},(@{self.channel_name})',
            get_cmd= f'CONF?',
            get_parser=self.configure_cmd_get_parser
        )

    def configure_cmd_get_parser(respose: str) -> dict:
        # regular expression that looks for "FREQ", and then extracts frequency, resolution, channel number
        raw_dict = re.match(...).group()
        output_dict = {"frequency": float(raw_dict["frequency"]), ...., ....}

        return output_dict

[pyquest1]

Hi Akisha07,

Thanks for the help. That solved the problem.

[Akshita07]

This issue is solved.