commit afde2f85e26fc9294e2f88ae1f9ee455f70323f8
Author: CPD <CPD@TUZEWSI-2LN203M.ads.mwn.de>
Date:   Tue Apr 29 12:25:57 2025 +0200

    Init

diff --git a/prsctl/measurement_device/__init__.py b/prsctl/measurement_device/__init__.py
new file mode 100644
index 0000000..2530581
--- /dev/null
+++ b/prsctl/measurement_device/__init__.py
@@ -0,0 +1,34 @@
+
+from .base import MeasurementDevice
+
+TYPENAME_TEST = "Test"
+TYPENAME_KEITHLEY2700 = "Keithley 2700"
+
+try:
+    from .impl.sr830 import SR830
+except ImportError:
+    pass
+
+from .impl.test import TestVoltageMeasurementDevice
+
+def list_devices() -> dict[str,list[str]]:
+    devices = {
+        TYPENAME_TEST: ["Voltage Measurement Dummy Device"],
+    }
+    try:
+        from .impl.sr830 import SR830
+        devices[TYPENAME_KEITHLEY2700] = SR830.enumerate_devices()
+    except ImportError:
+        pass
+    return devices
+
+def connect_device(type_name: str, device_name: str) -> MeasurementDevice:
+    if type_name == TYPENAME_TEST:
+        return TestVoltageMeasurementDevice()
+    elif type_name == TYPENAME_KEITHLEY2700:
+        try:
+            from .impl.sr830 import SR830
+            return SR830.connect_device(device_name)
+        except ImportError as e:
+            raise ValueError(f"Keithley 2700 devices not available: {e}")
+    raise ValueError(f"Unknown device type {type_name}")
\ No newline at end of file
diff --git a/prsctl/measurement_device/base.py b/prsctl/measurement_device/base.py
new file mode 100644
index 0000000..45901cb
--- /dev/null
+++ b/prsctl/measurement_device/base.py
@@ -0,0 +1,63 @@
+from abc import ABC, abstractmethod
+from typing import Callable
+
+"""
+Created on Tue Jan 21 16:19:01 2025
+
+@author: Matthias Quintern
+"""
+
+class MeasurementDevice(ABC):
+    @abstractmethod
+    def test_connection(self) -> None:
+        """
+        Verify that the device is still properly connected.
+        If not, raises ConnectionError
+        """
+        pass
+    # RUN COMMANDS ON THE DEVICE
+    @abstractmethod
+    def run(self, code, verbose=False):
+        pass
+    @abstractmethod   
+    def run_script(self, script_path, verbose=False):       
+        pass
+
+    @abstractmethod
+    def reset(self, verbose=False):
+        pass
+    
+    @abstractmethod
+    def read_value(self) -> tuple[float, float]:
+        """
+        Read a single value
+
+        Returns
+        -------
+        [timestamp, voltage]
+        """
+        pass
+
+    @abstractmethod
+    def measure(self, interval: int, update_func: Callable[None, [int, float, float]]|None=None, max_measurements:int|None=None):
+        """
+        Take voltage readings after <interval> milliseconds.
+
+        Parameters
+        ----------
+        interval : int
+            Number of milliseconds to wait between readings.
+        update_func : Callable[None, [int, float, float]] or None, optional
+            A function that is called after each reading with parameters <n_reading>, <time>, <voltage>. The default is None.
+        max_measurements : int or None, optional
+            Number of readings to perform. Set to None for infinite. The default is None.
+
+        Returns
+        -------
+        None.
+
+        """
+        pass
+    @abstractmethod
+    def __str__(self):
+        pass
\ No newline at end of file
diff --git a/prsctl/measurement_device/impl/sr830.py b/prsctl/measurement_device/impl/sr830.py
new file mode 100644
index 0000000..ab1d045
--- /dev/null
+++ b/prsctl/measurement_device/impl/sr830.py
@@ -0,0 +1,86 @@
+import pyvisa
+from time import sleep
+# import pkg_resources
+import os
+from typing import Callable
+
+from ..base import MeasurementDevice
+from ...utility.visa import enumerate_devices
+
+import logging
+log = logging.getLogger(__name__)
+
+class SR830(MeasurementDevice):
+    """
+    Wrapper class for the Keithley2700 SMU controlled via pyvisa
+    """
+    def __init__(self, instr, check_front_switch=True):
+        self.instr = instr
+        init_script = """
+        ' set input A
+        ISRC 0
+        ' set float
+        IGND 0
+        ' set AC coupling
+        ICPL 0
+        ' Enable 1x and 2x Line notch filters
+        ILIN 3
+        ' Enable synchronous filter < 200Hz
+        SYNC 1
+        ' Show R and Phase on the displays
+        DDEF 1 1 0
+        DDEF 2 1 0
+        ' Set sample rate to 256 Hz
+        12
+        ' Set buffer loop mode
+        SEND 1
+        """
+        self.run(init_script)
+
+    def __del__(self):
+        """Properly close the instrument connection"""
+        self.instr.close()
+
+    # RUN COMMANDS ON THE DEVICE
+    def run(self, code, verbose=False):
+        """
+        Run SCPI code on the device by writing it.
+        Empty lines, leading whitespaces and lines starting with ' or # are ignored.
+        Parameters
+        ----------
+        code : str
+            SCPI commands
+        """
+        script = ''
+        for line in code.strip(" ").split("\n"):
+            l = line.strip(" ")
+            if len(l) == 0 or l[0] in "#'": continue
+            script += l + "\n"
+        if verbose:
+            print(f"Running code:\n{script}")
+        try:
+            ret = self.instr.write(script)
+            if ret != 8:
+                raise RuntimeError(f"Error while writing command(s):\n'{script}'\n\nDevice returned code {ret}")
+        except pyvisa.VisaIOError as e:
+            raise RuntimeError(f"VisaIOError raised while writing command(s):\n'{script}'\n\nVisaIOError:\n{e}")
+
+    def get_frequency(self) -> float:
+        return float(self.query("FREQ?"))
+
+    def query(self, query):
+        return self.instr.query(query).strip("\n")
+
+
+    @staticmethod
+    def enumerate_devices(query="(GPIB)|(USB)?*:INSTR"):
+        return enumerate_devices("SR830", query)
+
+    @staticmethod
+    def connect_device(name):
+        rm = pyvisa.ResourceManager()
+        instr = rm.open_resource(name)
+        return SR830(instr)
+
+    def __str__(self):
+        return "SR830"
diff --git a/prsctl/measurement_device/impl/test.py b/prsctl/measurement_device/impl/test.py
new file mode 100644
index 0000000..6cb318c
--- /dev/null
+++ b/prsctl/measurement_device/impl/test.py
@@ -0,0 +1,60 @@
+from ..base import MeasurementDevice
+from typing import Callable
+from time import time as now
+import numpy as np
+
+class TestVoltageMeasurementDevice(MeasurementDevice):
+    def __init__(self, amplitude: float=1.0, frequency: float=20.0):
+        super().__init__()
+        self.amplitude = amplitude
+        self.frequency = frequency
+        self.t0 = now()
+
+    def test_connection(self) -> None:
+        pass
+
+    # RUN COMMANDS ON THE DEVICE
+    def run(self, code, verbose=False):
+        pass
+
+    def run_script(self, script_path, verbose=False):
+        pass
+
+    def reset(self, verbose=False):
+        pass
+
+    def read_value(self) -> tuple[float, float]:
+        """
+        Read a single value
+
+        Returns
+        -------
+        [timestamp, voltage]
+        """
+        t = now() - self.t0
+        v = self.amplitude * np.sin(2 * np.pi * t / self.frequency)
+        return t, v
+
+    def measure(self, interval: int, update_func: Callable[None, [int, float, float]] | None = None,
+                max_measurements: int | None = None):
+        """
+        Take voltage readings after <interval> milliseconds.
+
+        Parameters
+        ----------
+        interval : int
+            Number of milliseconds to wait between readings.
+        update_func : Callable[None, [int, float, float]] or None, optional
+            A function that is called after each reading with parameters <n_reading>, <time>, <voltage>. The default is None.
+        max_measurements : int or None, optional
+            Number of readings to perform. Set to None for infinite. The default is None.
+
+        Returns
+        -------
+        None.
+
+        """
+        pass
+
+    def __str__(self):
+        return "Simulated Voltage Measurement Device"
diff --git a/prsctl/utility/__init__.py b/prsctl/utility/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/prsctl/utility/config_file.py b/prsctl/utility/config_file.py
new file mode 100644
index 0000000..66c89ea
--- /dev/null
+++ b/prsctl/utility/config_file.py
@@ -0,0 +1,50 @@
+from os import environ, makedirs, path
+import yaml
+
+import logging
+log = logging.getLogger(__name__)
+class ConfigFile:
+    """
+    Class managing a yaml config file.
+    The file is loaded on creation and can be saved with .save().
+
+    You may initialize an instance with empty string as filepath,
+    in this case no file will not be loaded or saved.
+    """
+    def __init__(self, filepath: str, init_values = None):
+        self.values = {}
+        if init_values:
+            self.values = init_values
+        self.filepath = filepath
+        if path.isfile(self.filepath):
+            log.debug(f"[{self.filepath}] loading from file")
+            with open(self.filepath, "r") as file:
+                self.values |= yaml.safe_load(file)
+
+    def save(self):
+        if not self.filepath: return
+        directory = path.dirname(self.filepath)
+        if not path.isdir(directory):
+            makedirs(directory)
+        log.debug(f"[{self.filepath}] saving to file")
+        with open(self.filepath, "w") as file:
+            yaml.dump(self.values, file)
+
+    def get_or(self, name: str, default):
+        if name in self.values: return self.values[name]
+        return default
+
+    def get(self, name: str):
+        if name in self.values: return self.values[name]
+        raise KeyError(f"Key '{name}' not found in config file '{self.filepath}'")
+
+    def set(self, name: str, value):
+        log.debug(f"[{self.filepath}] set {name} = {value}")
+        self.values[name] = value
+
+    def get_values(self):
+        return self.values.copy()
+
+    def set_values(self, values):
+        log.debug(f"[{self.filepath}] set values = {values}")
+        self.values = values
\ No newline at end of file
diff --git a/prsctl/utility/data.py b/prsctl/utility/data.py
new file mode 100644
index 0000000..755bd5c
--- /dev/null
+++ b/prsctl/utility/data.py
@@ -0,0 +1,280 @@
+import pandas as pd
+import numpy as np
+import os
+import matplotlib.pyplot as plt
+import pickle
+import logging
+log = logging.getLogger(__name__)
+
+from cpdctrl.utility.file_io import get_next_filename, sanitize_filename
+
+FLUSH_TYPE = "pickle-ndarray"
+FLUSH_PREFIX = "PART_"
+METADATA_FILENAME = FLUSH_PREFIX + "measurement_metadata.pkl"
+
+class CpdData:
+    """
+    Class managing data and metadata.
+    Can be initialized from data directly, or a file or directory path.
+    """
+    columns = ["idx", "t [s]", "V [V]", "LED [%]"]
+    def __init__(self, path:str|None=None, data:np.ndarray|None=None, metadata:dict|None=None, verbose=False):
+        self.data = data
+        if type(metadata) == dict:
+            self.metadata = metadata
+        else:
+            self.metadata = {}
+        if data is None and path is None:
+            raise ValueError("Either path or data must be defined.")
+        if data is not None and path is not None:
+            raise ValueError("Either path or data must be defined, but not both.")
+        if path is not None:  # load from file
+            if os.path.isdir(path):
+                self.data, md = CpdData.load_data_from_dir(path, verbose=verbose)
+                self.metadata |= md
+            elif os.path.isfile(path):
+                if path.endswith(".csv"):
+                    self.data, md = CpdData.load_data_from_csv(path)
+                    self.metadata |= md
+                elif path.endswith(".pkl"):
+                    self.data, md = CpdData.load_data_from_pkl(path)
+                    self.metadata |= md
+                else:
+                    raise NotImplementedError(f"Only .csv and .pkl files are supported")
+            else:
+                raise FileNotFoundError(f"Path '{path}' is neither a file nor a directory.")
+        else:
+            self.data = data
+
+    # Convert data
+    def to_dataframe(self):
+        df = pd.DataFrame(self.data, columns=CpdData.columns)
+        df.meta = str(self.metadata)
+        return df
+
+    def to_csv(self, sep=","):
+        # self.to_dataframe().to_csv(os.path.join(self.path, self.name + ".csv"), index=False, metadata=True)
+        return CpdData.get_csv(self.data, self.metadata, sep=sep)
+
+
+    def save_csv_at(self, filepath, sep=",", verbose=False):
+        if verbose: print(f"Writing csv to {filepath}")
+        log.info(f"Writing csv to {filepath}")
+        with open(filepath, "w") as file:
+            file.write(self.to_csv(sep=sep))
+
+    def save_csv(self, sep=",", verbose=False):
+        """Save the csv inside the data directory"""
+        filepath = os.path.join(self.path, self.dirname + ".csv")
+        self.save_csv_at(filepath, sep, verbose)
+
+    # STATIC CONVERTER
+    @staticmethod
+    def get_csv(data, metadata, sep=","):
+        csv = ""
+        for k, v in metadata.items():
+            csv += f"# {k}: {v}\n"
+        csv += "".join(f"{colname}{sep}" for colname in CpdData.columns).strip(sep) + "\n"
+        for i in range(data.shape[0]):
+            csv += f"{i}{sep}{data[i,1]}{sep}{data[i,2]}{sep}{data[i,3]}\n"
+        return csv.strip("\n")
+
+    # STATIC LOADERS
+    @staticmethod
+    def load_data_from_csv(filepath:str, sep: str=",") -> tuple[np.ndarray, dict]:
+        """
+        Loads data from a single csv file.
+        Lines with this format are interpreted as metadata:
+            # key: value
+        Lines with this format are interpreted as data:
+            index, timestamp [s], CPD [V], LED [%]
+        Parameters
+        ----------
+        filepath
+           Path to the csv file.
+        sep
+            csv separator
+        Returns
+        -------
+        data
+            2D numpy array with shape (n, 4) where n is the number of data points.
+        metadata
+            Dictionary with metadata.
+        """
+        metadata = {}
+        with open(filepath, "r") as f:
+            # this loop will read the metadata at the beginning and skip also the header row
+            for line in f:
+                if line.startswith("#"):
+                    colon =  line.find(":")
+                    if colon == -1:  # normal comment
+                        continue
+                    key = line[1:colon].strip()
+                    value = line[colon+1:].strip()
+                    metadata[key] = value
+                else:
+                    break
+            # here, the generator has only data lines
+            data = np.loadtxt(f, delimiter=sep)
+        return data, metadata
+
+    @staticmethod
+    def load_data_from_pkl(filepath:str) -> tuple[np.ndarray, dict]:
+        """
+        Loads data from a single csv file.
+        Lines with this format are interpreted as metadata:
+            # key: value
+        Lines with this format are interpreted as data:
+            index, timestamp [s], CPD [V], LED [%]
+        Parameters
+        ----------
+        filepath
+           Path to the csv file.
+        sep
+            csv separator
+        Returns
+        -------
+        data
+            2D numpy array with shape (n, 4) where n is the number of data points.
+        metadata
+            Dictionary with metadata.
+        """
+        data = None
+        metadata = {}
+        with open(filepath, "rb") as f:
+            obj = pickle.load(f)
+        if isinstance(obj, tuple):
+            if not len(obj) == 2:
+                raise ValueError(f"Pickle file is a tuple with length {len(obj)}, however it must be 2: (data, metadata)")
+            data = obj[0]
+            metadata = obj[1]
+            if not isinstance(data, np.ndarray):
+                raise ValueError(f"First object in tuple is not a numpy.ndarray")
+        elif isinstance(obj, np.ndarray):
+            data = obj
+        else:
+            raise ValueError(f"Pickled object must be either numpy.ndarray or (numpy.ndarray, dict), but is of type {type(obj)}")
+        # must be loaded by now
+        if not len(data.shape) == 2 and data.shape[1] == 4:
+            raise ValueError(f"numpy.ndarray has invalid shape: {data.shape}, however the shape must be (N, 4)")
+        if not isinstance(metadata, dict):
+            raise ValueError(f"Metadata is not a of type dict")
+        return data, metadata
+
+    @staticmethod
+    def load_data_from_dir(dirpath:str, verbose:bool=False) -> tuple[np.ndarray, dict]:
+        """
+        Combines all data files with the FLUSH_PREFIX from a directory into a numpy array
+
+        Parameters
+        ----------
+        dirpath : str
+            Path to the data directory
+        verbose : bool, optional
+            If True, print a message for every file that is opened. The default is False.
+
+        Raises
+        ------
+        NotImplementedError
+            DESCRIPTION.
+
+        Returns
+        -------
+        data : ndarray
+            First index: Measurement
+            Second index: (index, timestamp [s], CPD [V], LED [%])
+        """
+        files = os.listdir(dirpath)
+        files.sort()
+        data = np.empty((0, 4))
+        metadata = {}
+        for filename in files:
+            filepath = os.path.join(dirpath, filename)
+            if filename.startswith(FLUSH_PREFIX):
+                if filename.endswith(".csv"):
+                    if verbose: print(f"Opening {filepath} as csv")
+                    df = pd.read_csv(filepath)
+                    arr = df.to_numpy()
+                    data = np.concatenate((data, arr))
+                elif filename.endswith(".ndarray.pkl"):
+                    with open(filepath, "rb") as file:
+                        arr = pickle.load(file)
+                        if len(arr.shape) != 2 or arr.shape[1] != 4:
+                            print(f"Skipping file '{filepath}' with invalid array shape: {arr.shape}")
+                            continue
+                        data = np.concatenate((data, arr))
+                elif filename == METADATA_FILENAME:  # Metadata filename must also start with FLUSH_PREFIX
+                    with open(filepath, "rb") as file:
+                        metadata = pickle.load(file)
+                else:
+                    raise NotImplementedError(f"Unknown file extension for file '{filepath}'")
+            else:
+                log.info(f"Skipping unknown file: '{filepath}'")
+        return data, metadata
+
+
+def plot_cpd_data(data: str or pd.DataFrame or np.ndarray, t: str="seconds", title: str="", CPD:bool=True, LED:bool=True):
+    """
+    Plot recorded data 
+
+    Parameters
+    ----------
+    data : str or np.ndarray
+        Path to the data directory or 
+        numpy array with columns (idx, t [s], V [V], LED [%])
+    t : str, optional
+        Which timescale to use for the x axis:
+        Must be one of "seconds", "mintutes", "hours".
+        The default is "seconds".
+    title : str, optional
+        Title for the plot. The default is "".
+    CPD : bool, optional
+        Wether to plot the voltage (CPD) line. The default is True.
+    LED : bool, optional
+        Wether to plot the LED state line. The default is False.
+
+    Returns
+    -------
+    fig : TYPE
+        Matplotlib figure object.
+    """
+    if type(data) == str:
+        _data, _ = CpdData.load_data_from_dir(data)
+    else:
+        _data = data
+    fig, ax = plt.subplots()
+    xdata = _data[:,1].copy()
+    xlabel = "t [s]"
+    if t == "minutes":
+        xdata /= 60
+        xlabel = "t [minutes]"
+    elif t == "hours":
+        xdata /= 3600
+        xlabel = "t [hours]"
+    ax.set_xlabel(xlabel)
+    ax_cpd = ax
+    ax_led = ax
+    if CPD and LED:
+        ax_led = ax.twinx()
+    if CPD:
+        ax_cpd = ax
+        ax_cpd.set_ylabel("CPD [V]")
+        ax_cpd.plot(xdata, _data[:,2], color="blue", label="CPD")
+    if LED:
+        ax_led.set_ylabel("LED [%]")
+        ax_led.plot(xdata, _data[:,3], color="orange", label="LED")
+        ax_led.set_ylim(-2, 102)
+        ax_led.set_yticks([0, 20, 40, 60, 80, 100])
+    if CPD and LED:
+        # ax_led.legend()
+        # ax_cpd.legend()
+        pass
+    if title:
+        ax.set_title(title)
+    fig.tight_layout()
+    return fig
+
+
+
+
+
diff --git a/prsctl/utility/data_collector.py b/prsctl/utility/data_collector.py
new file mode 100644
index 0000000..8a6954b
--- /dev/null
+++ b/prsctl/utility/data_collector.py
@@ -0,0 +1,141 @@
+import pandas as pd
+import numpy as np
+import os
+import datetime
+import pickle
+import logging
+log = logging.getLogger(__name__)
+
+from cpdctrl.utility.file_io import get_next_filename, sanitize_filename
+from cpdctrl.utility.data import CpdData, FLUSH_TYPE, FLUSH_PREFIX, METADATA_FILENAME
+
+
+class DataCollector:
+    """
+    Class managing data collection and partial storage
+    """
+    def __init__(self,
+                 data_path: str,
+                 data_name: str="CPData",
+                 metadata: dict[str, str]={},
+                 dirname: str|None=None,
+                 add_number_if_dir_exists=True,
+                 ):
+        self.data = []
+        self.cpd_data = None  # if loaded, this contains the final numpy array
+        self.name = data_name
+        self.metadata = metadata
+        self.path = os.path.abspath(os.path.expanduser(data_path))
+        if dirname is None:
+            self.dirname = sanitize_filename(datetime.datetime.now().strftime("%Y-%m-%d_%H-%M") + "_" + self.name)
+        else:
+            self.dirname = sanitize_filename(dirname)
+        self.dirpath = os.path.join(self.path, self.dirname)
+
+        if os.path.exists(self.dirpath):
+            if not add_number_if_dir_exists:
+                raise Exception(f"Directory '{self.dirname}' already exists. Provide a different directory or pass `add_number_if_dir_exists=True` to ignore this")
+            else:
+                i = 1
+                dirpath = f"{self.dirpath}-{i}"
+                while os.path.exists(dirpath):
+                    i += 1
+                    dirpath = f"{self.dirpath}-{i}"
+                    print(f"Directory '{self.dirname}' already exists. Trying '{dirpath}' instead")
+                self.dirpath = dirpath
+        self.assert_directory_exists()
+        self.flushed = False
+
+
+    # OPERATION
+    def clear(self):
+        self.data = []
+        self.cpd_data = None
+
+    def add_data(self, i, t, v, l):
+        self.data.append((i, t, v, l))
+        self.cpd_data = None  # no longer up to date
+
+    def flush(self, verbose: bool = False):
+        """
+        Write the current data to a file and clear the internal data
+
+        Parameters
+        ----------
+        verbose : bool, optional
+            If True, print a message when flushing data. The default is False.
+
+        Raises
+        ------
+        ValueError
+            If the FLUSH_TYPE is invalid.
+
+        Returns
+        -------
+        None.
+
+        """
+        # dont flush empty data
+        if len(self.data) == 0:
+            return
+        self.assert_directory_exists()
+        if FLUSH_TYPE == "csv":
+            filename = self._get_flush_filename() + ".csv"
+            filepath = os.path.join(self.dirpath, filename)
+            log.info(f"Flushing data to {filepath}")
+            if verbose: print(f"Flushing data to {filepath}")
+
+            df = pd.DataFrame(self.data, columns=CpdData.columns)
+            df.meta = str(self.metadata)
+            df.to_csv(filepath, sep=",", index=False, metadata=True)
+        elif FLUSH_TYPE == "pickle-ndarray":
+            filename = self._get_flush_filename() + ".ndarray.pkl"
+            filepath = os.path.join(self.dirpath, filename)
+            log.info(f"Flushing data to {filepath}")
+            if verbose: print(f"Flushing data to {filepath}")
+            with open(filepath, "wb") as file:
+                pickle.dump(np.array(self.data), file)
+        else:
+            raise ValueError(f"Invalid FLUSH_TYPE: '{FLUSH_TYPE}'")
+        self.clear()
+
+    # File IO
+    def _get_flush_filename(self):
+        """Get the filename of the next partial file, incrementing the number every time"""
+        return sanitize_filename(get_next_filename(FLUSH_PREFIX + self.name, self.dirpath, digits=5))
+
+    def assert_directory_exists(self):
+        if not os.path.isdir(self.dirpath):
+            os.makedirs(self.dirpath)
+
+    def get_data(self) -> CpdData:
+        """
+        Load the full data and return it together with the metadata
+        Returns
+        -------
+        tuple[np.ndarray, dict]
+           The full data and the metadata
+        """
+        if self.cpd_data is None:
+            self.cpd_data = CpdData(path=self.dirpath, metadata=self.metadata)
+        return self.cpd_data
+
+    def save_csv_in_dir(self, sep=",", verbose=False):
+        """Save full data as csv inside the directory with temporary data"""
+        self.get_data()
+        filepath = os.path.join(self.dirpath, self.dirname + ".csv")
+        self.cpd_data.save_csv_at(filepath, sep, verbose)
+
+    def write_metadata(self):
+        f"""
+        Write the metadata to the disk as '{METADATA_FILENAME}'
+
+        Returns
+        -------
+        None.
+        """
+        filepath = os.path.join(self.dirpath, METADATA_FILENAME)
+        log.debug(f"Writing metadata to {filepath}")
+        with open(filepath, "wb") as file:
+            pickle.dump(self.metadata, file)
+
diff --git a/prsctl/utility/device_select.py b/prsctl/utility/device_select.py
new file mode 100644
index 0000000..41646b3
--- /dev/null
+++ b/prsctl/utility/device_select.py
@@ -0,0 +1,26 @@
+def select_device_interactive(type_devices_dict: dict[str, list[str]], prompt="Select an instrument: ") -> tuple[str, str]:
+    """
+    Select a device interactively from the command line
+
+    Parameters
+    ----------
+    type_devices_dict
+        A dictionary of device types and their corresponding device names
+    -------
+    The type and name of the selected device.
+    These can be passed to the connect_device method of the led_control_device or voltage_measurement_device libraries
+    """
+    res = type_devices_dict
+    flat_res = [ (t, v) for t, l in res.items() for v in l ]
+    for i, (t,v) in enumerate(flat_res):
+        print(f"{i+1:02}: {t} - {v}")
+    while len(flat_res) > 0:
+        try:
+            instr = int(input(prompt)) - 1
+            if instr < 0 or instr >= len(flat_res):
+                raise ValueError
+            return flat_res[instr]
+        except ValueError:
+            print(f"Enter a number between 1 and {len(flat_res)}")
+            continue
+    raise Exception("No devices found")
\ No newline at end of file
diff --git a/prsctl/utility/file_io.py b/prsctl/utility/file_io.py
new file mode 100644
index 0000000..dfcf767
--- /dev/null
+++ b/prsctl/utility/file_io.py
@@ -0,0 +1,37 @@
+from os import listdir, path
+import re
+
+def add_zeros(v: int, digits=3):
+    """
+    return v as string, add leading zeros if len(str(v)) < digits
+    """
+    s = str(v)
+    return '0' * (max(digits - len(s), 0)) + s
+
+
+def get_next_filename(basename, directory=".", digits=3):
+    """
+    get the next filename (without extenstion).
+    example:
+        basename = file
+        directory has file001.csv, file002.bla.pkl, file004.csv
+        -> return file005
+    """
+    files = listdir(directory)
+    files.sort()
+    files.reverse()
+    lowest_number = -1
+    for file in files:
+        if not file.startswith(basename): continue
+        try:
+            number = file[:file.find('.')].replace(basename, "")
+            number = int(number)
+            if number < lowest_number: continue
+            lowest_number = number
+        except ValueError:
+            continue
+
+    return basename + add_zeros(lowest_number+1, digits)
+
+def sanitize_filename(filename):
+    return re.sub(r'[\\/*?:"<>|]',"", filename)
\ No newline at end of file
diff --git a/prsctl/utility/visa.py b/prsctl/utility/visa.py
new file mode 100644
index 0000000..e8cb2f2
--- /dev/null
+++ b/prsctl/utility/visa.py
@@ -0,0 +1,34 @@
+import pyvisa
+
+import logging
+log = logging.getLogger(__name__)
+
+def enumerate_devices(device_name, query="(GPIB)|(USB)?*:INSTR", visa_backend=""):
+    """
+    Return all available visa resources that match the query and the device name
+    Parameters
+    ----------
+    device_name
+        A part of the name that the device is supposed upon the '*IDN?' query
+    query
+        A query to the visa resource manager, to filter the resources
+    visa_backend
+        The visa backend to use, if not the default one
+
+    Returns
+    -------
+    List of visa resource names
+
+    """
+    rm = pyvisa.ResourceManager(visa_backend)
+    res = []
+    for r in rm.list_resources(query):
+        try:
+            instr = rm.open_resource(r)
+            name = instr.query('*IDN?')
+            if device_name in name:
+                res.append(r)
+            instr.close()
+        except:
+            log.debug(f"Could not open Visa resources {r}")
+    return res
\ No newline at end of file