hvl_ccb.comm.visa

Communication protocol for VISA. Makes use of the pyvisa library. The backend can be NI-Visa or pyvisa-py.

Information on how to install a VISA backend can be found here: https://pyvisa.readthedocs.io/en/master/getting_nivisa.html

So far only TCPIP SOCKET and TCPIP INSTR interfaces are supported.

class VisaCommunication(configuration)

Bases: CommunicationProtocol

Implements the Communication Protocol for VISA / SCPI.

MULTI_COMMANDS_MAX = 5

The maximum of commands that can be sent in one round is 5 according to the VISA standard.

MULTI_COMMANDS_SEPARATOR = ';'

The character to separate two commands is ; according to the VISA standard.

WAIT_AFTER_WRITE = 0.08

Small pause in seconds to wait after write operations, allowing devices to really do what we tell them before continuing with further tasks.

close() → None

Close the VISA connection and invalidates the handle.

static config_cls() → type[VisaCommunicationConfig]

Return the default configdataclass class.

Returns:

a reference to the default configdataclass class

open() → None

Open the VISA connection and create the resource.

query(*commands: str) → str | tuple[str, ...]

A combination of write(message) and read.

Parameters:

commands – list of commands

Returns:

list of values

Raises:

VisaCommunicationError – when connection was not started, or when trying to issue too many commands at once.

spoll() → int

Execute serial poll on the device. Reads the status byte register STB. This is a fast function that can be executed periodically in a polling fashion.

Returns:

integer representation of the status byte

Raises:

VisaCommunicationError – when connection was not started

write(*commands: str) → None

Write commands. No answer is read or expected.

Parameters:

commands – one or more commands to send

Raises:

VisaCommunicationError – when connection was not started

class VisaCommunicationConfig(host: str | IPv4Address | IPv6Address, interface_type: str | InterfaceType, board: int = 0, port: int = 5025, timeout: int = 5000, chunk_size: int = 204800, open_timeout: int = 1000, write_termination: str = '\n', read_termination: str = '\n', visa_backend: str = '')

Bases: object

VisaCommunication configuration dataclass.

class InterfaceType(value=<no_arg>, names=None, module=None, qualname=None, type=None, start=1, boundary=None)

Bases: AutoNumberNameEnum

Supported VISA Interface types.

TCPIP_INSTR = 2

VXI-11 protocol

TCPIP_SOCKET = 1

VISA-RAW protocol

address(host: str, port: int | None = None, board: int | None = None) → str

Address string specific to the VISA interface type.

Parameters:

• host – host IP address

• port – optional TCP port

• board – optional board number

Returns:

address string

property address: str

Address string depending on the VISA protocol’s configuration.

Returns:

address string corresponding to current configuration

board: int = 0

Board number is typically 0 and comes from old bus systems.

chunk_size: int = 204800

Chunk size is the allocated memory for read operations. The standard is 20kB, and is increased per default here to 200kB. It is specified in bytes.

clean_values()

force_value(fieldname, value)

Forces a value to a dataclass field despite the class being frozen.

NOTE: you can define post_force_value method with same signature as this method to do extra processing after value has been forced on fieldname.

Parameters:

• fieldname – name of the field

• value – value to assign

host: str | IPv4Address | IPv6Address

interface_type: str | InterfaceType

Interface type of the VISA connection, being one of InterfaceType.

is_configdataclass = True

classmethod keys() → Sequence[str]

Returns a list of all configdataclass fields key-names.

Returns:

a list of strings containing all keys.

open_timeout: int = 1000

Timeout for opening the connection, in milli seconds.

classmethod optional_defaults() → dict[str, object]

Returns a list of all configdataclass fields, that have a default value assigned and may be optionally specified on instantiation.

Returns:

a list of strings containing all optional keys.

port: int = 5025

TCP port, standard is 5025.

read_termination: str = '\n'

Read termination character.

classmethod required_keys() → Sequence[str]

Returns a list of all configdataclass fields, that have no default value assigned and need to be specified on instantiation.

Returns:

a list of strings containing all required keys.

timeout: int = 5000

Timeout for commands in milli seconds.

visa_backend: str = ''

Specifies the path to the library to be used with PyVISA as a backend. Defaults to None, which is NI-VISA (if installed), or pyvisa-py (if NI-VISA is not found). To force the use of pyvisa-py, specify ‘@py’ here.

write_termination: str = '\n'

Write termination character.

exception VisaCommunicationError

Bases: OSError, CommunicationError

Base class for VisaCommunication errors.