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 connect_to_names_pv(self):
     """Connects amonitor to the block-server to get the names of the blocks.
     """
     def _blocknames_callback(epics_args, user_args):
         names = json.loads(dehex_and_decompress(waveform_to_string(epics_args['pv_value'])))
         if self.block_names is None or names != self.block_names:
             self.block_names = names
             print "Updated"
     
     chan = CaChannel("BLOCKNAMES")
     chan.searchw("%s%s" % (self.prefix, "CS:BLOCKSERVER:BLOCKNAMES"))
     chan.add_masked_array_event(
         ca.DBR_CHAR,
         None,
         ca.DBE_VALUE | ca.DBE_ALARM,
         _blocknames_callback)
         
     chan.pend_event(PEND_EVENT_TIMEOUT)
Example #3
0
class pv():
    # Wrapper for associating CaChannel class to specific PV using its name 
    def __init__(self, pvname):
        try:
            self.pv = CaChannel()
            self.pv.searchw(pvname)
            self.alarm_status = "n/a"	# used to store severity provided by callback
            self.alarm_severity = "n/a"	# used to store severity provided by callback
        except :
            raise Exception("****** PV not found - "+pvname+" ******")
        #return pv
  
    # Wrapper for putw() function - writing a value to PV and waiting for input records to scan (update their value)
    def write(self, *args):
        try:
            if len(args) == 2:  # arguments: value, scan_time
                self.pv.putw(args[0])
                time.sleep(args[1])
            if len(args) == 3:  # arguments: value, scan_time, type
                if args[2] == "STRING":
                    self.pv.putw(args[0],ca.DBR_STRING)
                else:
                    raise Exception("Type "+ str(args[3]) +" not recognized")
                time.sleep(args[1])
            print("***W: Set  PV "+self.pv.name()+" to    "+str(args[0]))
        except:
            print("Could not set PV "+self.pv.name()+" to "+str(args[0]))
    
    # Similar to write() except it does not print output when successfully sets the value
    # Useful for setUp and tearDown methods
    def write_silent(self, *args):
        try:
            if len(args) == 2:  # arguments: value, scan_time
                self.pv.putw(args[0])
                time.sleep(args[1])
            if len(args) == 3:  # arguments: value, scan_time, type
                if args[2] == "STRING":
                    self.pv.putw(args[0],ca.DBR_STRING)
                else:
                    raise Exception("Type "+ str(args[3]) +" not recognized")
                time.sleep(args[1])
        except:
            print("Could not set PV "+self.pv.name()+" to "+str(args[0]))
    
    # Wrapper for getw()
    def read(self, *args):
        if len(args) == 1:
            if args[0] == "STRING":
                val = self.pv.getw(ca.DBR_STRING)
            else:
                raise Exception("Type "+ str(args[3]) +" not recognized")
            print("***R: Read PV "+self.pv.name()+" value "+str(val))
            return val
        else:
            val = self.pv.getw()
            print("***R: Read PV "+self.pv.name()+" value "+str(val))
            return val
            
    # Wrapper for getw() with CALLBACK for alarm status/severity
    def read_alarm(self):
        self.pv.array_get_callback(ca.dbf_type_to_DBR_STS(self.pv.field_type()), None, Callback, self)
        self.pv.flush_io()
        for i in range(20):
            self.pv.pend_event()
    
    # Wrapper for name()
    def name(self):
        return self.pv.name()