pcdsdevices.signal.PytmcSignal

class pcdsdevices.signal.PytmcSignal(prefix, io=None, **kwargs)

Class for a connection to a pytmc-generated EPICS record.

This uses the same args as the pragma, so you can refer to the pytmc pragmas to select args for your components. This will automatically append the ‘_RBV’ suffix and wrap the read/write PVs into the same signal object as appropriate, and pick between a read-only signal and a writable one.

Under the hood this actually gives you the RW or RO version of the signal depending on your io argument.

Methods

describe()

Return the description as a dictionary

Returns:

dict – Dictionary of name and formatted description string

get(*, count=None, as_string=None, timeout=<object object>, connection_timeout=<object object>, form='time', use_monitor=None, **kwargs)

Get the readback value through an explicit call to EPICS.

Parameters:

  • count (int, optional) – Explicitly limit count for array data

  • as_string (bool, optional) – Get a string representation of the value, defaults to as_string from this signal, optional

  • as_numpy (bool) – Use numpy array as the return type for array data.

  • timeout (float, optional) – maximum time to wait for value to be received. (default = 0.5 + log10(count) seconds)

  • use_monitor (bool, optional) – to use value from latest monitor callback or to make an explicit CA call for the value. (default: True)

  • connection_timeout (float, optional) – If not already connected, allow up to connection_timeout seconds for the connection to complete.

  • form ({'time', 'ctrl'}) – PV form to request

read()

Put the status of the signal into a simple dictionary format for data acquisition

Returns:

dict

read_configuration()

Dictionary mapping names to value dicts with keys: value, timestamp

set(value, *, timeout=None, settle_time=None, **kwargs)

Set the value of the Signal and return a Status object.

Returns:

st (Status) – This status object will be finished upon return in the case of basic soft Signals

classmethod set_default_timeout(**kwargs)
classmethod set_defaults(*, timeout=2.0, connection_timeout=1.0, write_timeout=None, auto_monitor=False)

Set class-wide defaults for EPICS CA communications

This may be called only before any instances of EpicsSignalBase are made.

This setting applies to the class it is called on and all its subclasses. For example,

>>> EpicsSignalBase.set_defaults(...)

will apply to EpicsSignalRO and EpicsSignal, which are both subclasses of EpicsSignalBase.

but

>>> EpicsSignal.set_defaults(...)

will not apply to EpicsSignalRO.

Parameters:

  • auto_monitor (bool, optional) – If True, update cached value from EPICS CA monitor callbacks. If False, request new value from EPICS each time get() is called.

  • connection_timeout (float, optional) – Time (seconds) allocated for establishing a connection with the IOC.

  • timeout (float, optional) – Total time budget (seconds) for reading, not including connection time.

  • write_timeout (float, optional) – Time (seconds) allocated for writing, not including connection time. The write_timeout is very different than the connection and read timeouts above. It relates to how long an action takes to complete. Any default value we choose here is likely to cause problems—either by being too short and giving up too early on a lengthy action or being too long and delaying the report of a failure. The default, None, waits forever.

Raises:

RuntimeError – If called after EpicsSignalBase has been instantiated for the first time.

trigger()

Call that is used by bluesky prior to read()

Attributes

SUB_META = 'meta'
alarm_severity

PV alarm severity

alarm_status

PV status

as_string

Attempt to cast the EPICS PV value to a string by default

connected

Is the signal connected to its associated hardware, and ready to use?

connection_timeout
enum_strs

List of strings if PV is an enum type

high_limit

The high, inclusive control limit for the Signal

hints

Field hints for plotting

kind
limits

The PV control limits (low, high), such that low <= value <= high

low_limit

The low, inclusive control limit for the Signal

metadata

A copy of the metadata dictionary associated with the signal

metadata_keys

Metadata keys that will be passed along on value subscriptions

precision

The precision of the read PV, as reported by EPICS

pvname

The readback PV name

read_access

Can the signal be read?

source_name
subscriptions: ClassVar[FrozenSet[str]] = frozenset({'meta', 'value'})
timeout
timestamp

Timestamp of readback PV, according to EPICS

tolerance

The absolute tolerance associated with the value.

value

The signal’s value

write_access

Can the signal be written to?

write_timeout