improve lakeshore demo

use super call for read_status

TODO: update tutorial!
Change-Id: I2dd5631908dc370c6e6286587099e25a0e5ee867

frappy_demo/lakeshore.py

@@ -69,14 +69,16 @@ class TemperatureLoop(TemperatureSensor, Drivable):
     # lakeshore loop number to be used for this module
     loop = Property('lakeshore loop', IntRange(1, 2), default=1)
     target = Parameter(datatype=FloatRange(unit='K', min=0, max=1500))
-    heater_range = Property('heater power range', IntRange(0, 5))  # max. 3 on LakeShore 336
+    heater_range = Property('heater power range', IntRange(0, 3), readonly=False)
     tolerance = Parameter('convergence criterion', FloatRange(0), default=0.1, readonly=False)
     _driving = False
 
+    def write_heater_range(self, value):
+        self.communicate(f'RANGE {self.loop},{value};RANGE?{self.loop}')
+
     def write_target(self, target):
         # reactivate heater in case it was switched off
-        # the command has to be changed in case of model 340 to f'RANGE {self.heater_range};RANGE?'
-        self.communicate(f'RANGE {self.loop},{self.heater_range};RANGE?{self.loop}')
+        self.write_heater_range(self.heater_range)
         self.communicate(f'SETP {self.loop},{target};*OPC?')
         self._driving = True
         # Setting the status attribute triggers an update message for the SECoP status
@@ -85,23 +87,21 @@ class TemperatureLoop(TemperatureSensor, Drivable):
         return target
 
     def read_status(self):
-        code = int(self.communicate(f'RDGST?{self.channel}'))
-        if code >= 128:
-            text = 'units overrange'
-        elif code >= 64:
-            text = 'units zero'
-        elif code >= 32:
-            text = 'temperature overrange'
-        elif code >= 16:
-            text = 'temperature underrange'
-        elif code % 2:
-            # ignore 'old reading', as this may happen in normal operation
-            text = 'invalid reading'
-        elif abs(self.target - self.value) > self.tolerance:
+        status = super().read_status()
+        if status[0] == ERROR:
+            return status
+        if abs(self.target - self.value) > self.tolerance:
             if self._driving:
                 return BUSY, 'approaching setpoint'
             return WARN, 'temperature out of tolerance'
-        else:  # within tolerance: simple convergence criterion
-            self._driving = False
-            return IDLE, ''
-        return ERROR, text
+        # within tolerance: simple convergence criterion
+        self._driving = False
+        return IDLE, ''
+
+
+class TemperatureLoop340(TemperatureLoop):
+    # slightly different behaviour for model 340
+    heater_range = Property('heater power range', IntRange(0, 5))
+
+    def write_heater_range(self, value):
+        self.communicate(f'RANGE {value};RANGE?')