How to integrate InstrumentChannel class into VisaInstrument class

[paniash]

Hi all,

I'm very new to QCoDeS, so kindly excuse my ignorance.

I'm writing a driver for an oscilloscope with four channels and have defined an InstrumentChannel class containing all the parameters and another VisaInstrument class following the example given in the docs.

However, when writing a script by importing the VisaInstrument class, I'm not exactly sure how I can define channels in the main VisaInstrument class.

Here's the relevant driver file (keysight/Keysight_DSOX4104A.py and test-script.py): https://gitlab.com/paniash/qcode-drivers/-/tree/main/keysight

Thanks in advance!

[jenshnielsen]

If you look at the example that you have linked you should see inside
the Keithley2600 class.

    # Add the channel to the instrument
    for ch in ["a", "b"]:
        ch_name = f"smu{ch}"
        channel = KeithleyChannel(self, ch_name, ch_name)
        self.add_submodule(ch_name, channel)

This addes submodules smua and smub that you can then access as instrument.a and instrument.b when you have initialized the instrument.

[paniash]

Hi @jenshnielsen! Thanks for the reply. I'm trying to define the instrument with

osc = KeysightDSOX4104A(name="osc", address="TCPIP0::a-dx4104a-60137::INSTR",
                        channel=[1, 2, 3, 4])

However, I get an error stating that a channel attribute does not exist. How would I go ahead defining channels in this case?

[jenshnielsen]

In the code that you have linked you have

class KeysightDSOX4104A(VisaInstrument):
    """
    This is the qcodes driver for the Keysight InfiniiVision DSOX4104A oscilloscope
    """

    def __init__(self, name: str, address: str, **kwargs) -> None:
        """
        Args:
            name: Name used internally by QCoDeS
            address: VISA resource address
        """
        super().__init__(name, address, terminator="\n", **kwargs)

        # Add channel to instrument
        for ch in [1, 2, 3, 4]:
            ch_name = f"ch{ch}"
            channel = DSOX4104AChannel(self, ch_name, ch)
            self.add_submodule(ch, channel)
            self.channels.append(channel)

Here you are trying to add the channel that you have created to a list of channels in the last line but you have never devined than list any where.

Now there are two alternatives. You don't need that line without it you will still be able to access the channels as osc.ch1 etc.

You only need that line if you want to be able to access the channels by index or set a value on more than one channel in the same operation. E.g do osc.channels[0] to do that you should make that variable a ChannelList or ChannelTuple.

https://qcodes.github.io/Qcodes/api/instrument/index.html#qcodes.instrument.ChannelTuple

One way could be:

class KeysightDSOX4104A(VisaInstrument):
    """
    This is the qcodes driver for the Keysight InfiniiVision DSOX4104A oscilloscope
    """

    def __init__(self, name: str, address: str, **kwargs) -> None:
        """
        Args:
            name: Name used internally by QCoDeS
            address: VISA resource address
        """
        super().__init__(name, address, terminator="\n", **kwargs)
        channels = []
        # Add channel to instrument
        for ch in [1, 2, 3, 4]:
            ch_name = f"ch{ch}"
            channel = DSOX4104AChannel(self, ch_name, ch)
            self.add_submodule(ch, channel)
            channels.append(channel)
       channel_tuple = ChannelTuple(self, "channels", DSOX4104AChannel, channels)
       self.add_submodule("channels", channel_tuple)

You do not need to and should not pass channel=[1, 2, 3, 4] as an argument when you initialize the Instrument Class

[paniash]

Thanks! May I ask about the other alternative where I could access the channels as osc.ch1? Currently without your suggested code, I get the error:

'KeysightDSOX4104A' object and its delegates have no attribute 'ch1'

[jenshnielsen]

Could you check the value of osc.submodules this should be a dictionary that maps from the name ch1 to the modules/channels
if things work correctly.

[paniash]

Ah, I see. So the output of osc.submodules yields:

{1: <DSOX4104AChannel: osc_ch1 of KeysightDSOX4104A: osc>, 2: <DSOX4104AChannel: osc_ch2 of KeysightDSOX4104A: osc>, 3: <DSOX4104AChannel: osc_ch3 of KeysightDSOX4104A: osc>, 4: <DSOX4104AChannel: osc_ch4 of KeysightDSOX4104A: osc>, 'channels': ChannelTuple(<KeysightDSOX4104A: osc>, DSOX4104AChannel, [<DSOX4104AChannel: osc_ch1 of KeysightDSOX4104A: osc>, <DSOX4104AChannel: osc_ch2 of KeysightDSOX4104A: osc>, <DSOX4104AChannel: osc_ch3 of KeysightDSOX4104A: osc>, <DSOX4104AChannel: osc_ch4 of KeysightDSOX4104A: osc>])}

My channels are named 1, 2, 3, 4 instead of ch1, ch2, ch3, ch4. Makes sense why I can't access them as osc.1.

[jenshnielsen]

That is caused by your line 180. Here self.add_submodule(ch, channel) should have been self.add_submodule(ch_name, channel)

If you do that you can remove these lines

        self.ch1 = self.channels[0]
        self.ch2 = self.channels[1]
        self.ch3 = self.channels[2]
        self.ch4 = self.channels[3]

I recommend doing that since that will ensure that your snapshot is consistent