def set_pv_value(self, name, value, wait=False, timeout=TIMEOUT):
"""Set the PV to a value.
When getting a PV value this call should be used, unless there is a special requirement.
Parameters:
name - the PV name
value - the value to set
wait - wait for the value to be set before returning
"""
name = MYPVPREFIX + ':' + name
if name not in CACHE.keys():
chan = CaChannel(name)
chan.setTimeout(TIMEOUT)
#Try to connect - throws if cannot
chan.searchw()
CACHE[name] = chan
else:
chan = CACHE[name]
if wait:
chan.putw(value)
else:
def putCB(epics_args, user_args):
#Do nothing in the callback
pass
ftype = chan.field_type()
ecount = chan.element_count()
chan.array_put_callback(value, ftype, ecount, putCB)
chan.flush_io()
def get_pv_value(self, name, to_string=False, timeout=TIMEOUT):
"""Get the current value of the PV"""
name = MYPVPREFIX + ':' + name
if name not in CACHE.keys():
chan = CaChannel(name)
chan.setTimeout(TIMEOUT)
#Try to connect - throws if cannot
chan.searchw()
CACHE[name] = chan
else:
chan = CACHE[name]
ftype = chan.field_type()
if ca.dbr_type_is_ENUM(ftype) or ca.dbr_type_is_CHAR(
ftype) or ca.dbr_type_is_STRING(ftype):
to_string = True
if to_string:
if ca.dbr_type_is_ENUM(ftype):
value = chan.getw(ca.DBR_STRING)
else:
value = chan.getw(ca.DBR_CHAR)
#Could see if the element count is > 1 instead
if isinstance(value, list):
return self._waveform2string(value)
else:
return str(value)
else:
return chan.getw()
def _initialise_channel(self, name):
"""Initialises the channel by creating a connection callback.
Args:
name (string): The name of the PV to connect to.
"""
def _block_connection_callback(epics_args, user_args):
connection_state = epics_args[1]
if connection_state == ca.CA_OP_CONN_UP:
print ca.name(epics_args[0]), "UP"
# First time through creates the monitor
if ca.name(epics_args[0]) not in self.curr_values:
self._create_monitor(user_args[0], ca.name(epics_args[0]))
else:
print ca.name(epics_args[0]), "DOWN"
self.curr_lock.acquire()
try:
self.curr_values[ca.name(epics_args[0])] = ("*** disconnected", None)
except:
# Don't care, it is all about releasing the lock
pass
finally:
# Must release lock
self.curr_lock.release()
chan = CaChannel()
chan.setTimeout(EXISTS_TIMEOUT)
print "initialising %s" % name
try:
chan.search_and_connect(name, _block_connection_callback, chan)
chan.pend_event(PEND_EVENT_TIMEOUT)
return chan
except:
print "Could not connect"
return None
def _caget(pvname, as_string=False):
"""Retrieve an EPICS PV value"""
try:
from CaChannel import CaChannel, CaChannelException, ca
except ImportError:
raise RuntimeError("CaChannel must be installed to use this algorithm. "
"For details, see https://www.mantidproject.org/CaChannel_In_Mantid")
if as_string:
dbr_type = ca.DBR_STRING
else:
dbr_type = None
try:
chan = CaChannel(pvname)
chan.setTimeout(5.0)
chan.searchw()
return chan.getw(dbr_type)
except CaChannelException as e:
raise RuntimeError("Error reading EPICS PV \"{}\": {}".format(pvname, str(e)))