Merge pull request #7 from OE-FET/master

A few bug fixes and consistency improvements

Author: SamSchott

CHANGES.txt

@@ -1,4 +1,5 @@
+v0.2.3  21.07.2020 -- Fixed a possible issue when parsing alarms, set connection to None if not connected, improved thread safety when connecting to or disconnecting from device.
 v0.2.2  04.12.2019 -- Remember PyVisa connection settings passed to constructor between disconnects. Improved thread safety.
 v0.2.1, 30.04.2019 -- Moved controls for LOOP module to TEMP module.
-v0.2.0, 09.02.2019 -- Use pyvisa as communication protocol, added support for LOOP module, singleton behaviour when instanciating the device (all credit goes to Sam Schott for this release)
+v0.2.0, 09.02.2019 -- Use pyvisa as communication protocol, added support for LOOP module, singleton behaviour when instantiating the device (all credit goes to Sam Schott for this release)
 v0.1.0, 18.03.2014 -- Initial release.

mercuryitc/__init__.py

@@ -1,3 +1,3 @@
-__version__ = '0.2.2'
+__version__ = '0.2.3'
 
 from mercuryitc.mercury_driver import MercuryITCFactory as MercuryITC

mercuryitc/mercury_driver.py

@@ -779,8 +779,7 @@ class MercuryITC(MercuryCommon):
     DIMAS = ['ON', 'OFF']
     _lock = threading.RLock()
 
-    connected = True
-    connection = False
+    connection = None
 
     address = 'SYS'
 
@@ -800,32 +799,32 @@ def connect(self, **kwargs):
         kwargs = kwargs or self._connection_kwargs  # use specified or remembered kwargs
         connection_error = OSError if PY2 else ConnectionError
 
-        try:
-            self.connection = self.rm.open_resource(self.visa_address, **kwargs)
-            self.connection.read_termination = '\n'
-            self.connected = True
-            self._init_modules()
-        except connection_error:
-            logger.info('Connection to the instrument failed. Please check ' +
-                        'that no other programm is connected.')
-            self.connection = None
-            self.connected = False
-        except AttributeError:
-            logger.info('Invalid VISA address %s.' % self.visa_address)
-            self.connection = None
-            self.connected = False
-        except Exception:
-            logger.info('Could not connect to Mercury at %s.' % self.visa_address)
-            self.connection = None
-            self.connected = False
+        with self._lock:
+            try:
+                self.connection = self.rm.open_resource(self.visa_address, **kwargs)
+                self.connection.read_termination = '\n'
+                self._init_modules()
+            except connection_error:
+                logger.info('Connection to the instrument failed. Please check ' +
+                            'that no other program is connected.')
+                self.connection = None
+            except AttributeError:
+                logger.info('Invalid VISA address %s.' % self.visa_address)
+                self.connection = None
+            except Exception:
+                logger.info('Could not connect to Mercury at %s.' % self.visa_address)
+                self.connection = None
 
     def disconnect(self):
-        self.connected = False
-        try:
-            self.connection.close()
-            del self.connection
-        except AttributeError:
-            pass
+
+        with self._lock:
+            if self.connection:
+                self.connection.close()
+                self.connection = None
+
+    @property
+    def connected(self):
+        return self.connection is not None
 
     def _init_modules(self):
         self.modules = []
@@ -841,18 +840,27 @@ def _init_modules(self):
                 self.modules.append(MercuryITC_HTR(address, self))
 
     def write(self, q):
+
         with self._lock:
+            if not self.connection:
+                raise ConnectionError('Not connected to device.')
             self.connection.write(q)
 
     def read(self):
+
         with self._lock:
+            if not self.connection:
+                raise ConnectionError('Not connected to device.')
             return self.connection.read()
 
     def query(self, q):
+
         with self._lock:
+            if not self.connection:
+                raise ConnectionError('Not connected to device.')
             r = self.connection.query('%s' % q)
             self.connection.clear()
-        return r
+            return r
 
     @property
     def cat(self):
@@ -996,9 +1004,9 @@ def date(self, val):
     @property
     def alarms(self):
         """Gets the system alarms log"""
-        string = self._read_property('ALRM', str)
-        alarm_list = string[:-1].split(';')
-        alarms_dict = dict(item.split('\t') for item in alarm_list)
+        value = self._read_property('ALRM', str)
+        string_list = value.split(';')
+        alarms_dict = dict(s.split('\t') for s in string_list if s)
         return alarms_dict
 
 

setup.py

@@ -5,7 +5,7 @@
 # Sam Schott <ss2151@cam.ac.uk>
 
 setup(name="mercuryitc",
-      version='0.2.2',
+      version='0.2.3',
       description="Full Python driver for the Oxford Mercury iTC cryogenic environment controller.",
       author='Florian Forster, Sam Schott',
       maintainer='Florian Forster',