Driver Utils¶

class instrumental.drivers.VisaMixin¶

query(message, *args, **kwds)¶

Query the instrument’s VISA resource with message

Flushes the message queue if called within a transaction.

transaction(**kwds)¶

Transaction context manager to auto-chain VISA messages

Queues individual messages written with the write() method and sends them all at once, joined by ‘;’. Messages are actually sent (1) when a call to query() is made and (2) upon the end of transaction.

This is especially useful when using higher-level functions that call write(), as it lets you combine multiple logical operations into a single message (if only using writes), which can be faster than sending lots of little messages.

Be cognizant that a visa resource’s write and query methods are not transaction-aware, only VisaMixin’s are. If you need to call one of these methods (e.g. write_raw), make sure you flush the message queue manually with _flush_message_queue().

As an example:

>>> with myinst.transaction():
...     myinst.write('A')
...     myinst.write('B')
...     myinst.query('C?')  # Query forces flush. Writes "A;B" and queries "C?"
...     myinst.write('D')
...     myinst.write('E')  # End of transaction block, writes "D;E"

write(message, *args, **kwds)¶

Write a string message to the instrument’s VISA resource

Calls format(*args, **kwds) to format the message. This allows for clean inclusion of parameters. For example:

>>> inst.write('source{}:value {}', channel, value)

resource¶: VISA resource

Helpful utilities for writing drivers.

instrumental.drivers.util.check_units(*pos, **named)¶

Decorator to enforce the dimensionality of input args and return values.

Allows strings and anything that can be passed as a single arg to pint.Quantity.

@check_units(value='V')
def set_voltage(value):
    pass  # `value` will be a pint.Quantity with Volt-like units

instrumental.drivers.util.unit_mag(*pos, **named)¶

Decorator to extract the magnitudes of input args and return values.

Allows strings and anything that can be passed as a single arg to pint.Quantity.

@unit_mag(value='V')
def set_voltage(value):
    pass  # The input must be in Volt-like units and `value` will be a raw number
          # expressing the magnitude in Volts

instrumental.drivers.util.check_enums(**kw_args)¶

Decorator to type-check input arguments as enums.

Allows strings and anything that can be passed to as_enum.

@check_enums(mode=SampleMode)
def set_mode(mode):
    pass  # `mode` will be of type SampleMode

instrumental.drivers.util.as_enum(enum_type, arg)¶: Check if arg is an instance or key of enum_type, and return that enum

instrumental.drivers.util.visa_timeout_context(*args, **kwds)¶

Context manager for temporarily setting a visa resource’s timeout.

with visa_timeout_context(rsrc, 100):
     ...  # `rsrc` will have a timeout of 100 ms within this block