frappy_psi.ah2700: fixes

frappy_psi/ah2700.py

@@ -29,7 +29,7 @@ an empty name
 """
 
 from frappy.core import FloatRange, HasIO, Parameter, Readable, StringIO, nopoll, \
-    Attached, Property, StringType
+    Attached, Property, StringType, Writable
 from frappy.dynamic import Pinata
 
 
@@ -47,6 +47,11 @@ class Capacitance(HasIO, Pinata, Readable):
                          configure '' to disable the creation of the loss module
                          ''',
                          StringType(), default='$_loss')
+    freq_name = Property('''name of freq module
+
+                         default: not created
+                         ''',
+                         StringType(), default='')
 
     ioClass = Ah2700IO
     loss = 0  # not a parameter
@@ -59,6 +64,11 @@ class Capacitance(HasIO, Pinata, Readable):
                 'cls': Loss,
                 'description': f'loss value of {self.name}',
                 'cap': self.name}
+        if self.freq_name:
+            yield self.freq_name.replace('$', self.name), {
+                'cls': Freq,
+                'description': f'freq module of {self.name}',
+                'cap': self.name}
 
     def parse_reply(self, reply):
         if reply.startswith('SI'):  # this is an echo
@@ -76,17 +86,17 @@ class Capacitance(HasIO, Pinata, Readable):
         # split() ignores multiple white space
         reply = reply.replace('=', '= ').replace('>', '> ').split()
         _, freq, _, _, cap, _, _, loss, lossunit, _, volt = reply[:11]
-        self.freq = freq
-        self.voltage = volt
+        self.freq = float(freq)
+        self.voltage = float(volt)
         if lossunit == 'DS':
-            self.loss = loss
+            self.loss = float(loss)
         else:  # the unit was wrong, we want DS = tan(delta), not NS = nanoSiemens
             reply = self.communicate('UN DS').split()  # UN DS returns a reply similar to SI
             try:
                 self.loss = reply[7]
             except IndexError:
                 pass  # don't worry, loss will be updated next time
-        return cap
+        return float(cap)
 
     def read_value(self):
         return self.parse_reply(self.communicate('SI'))  # SI = single trigger
@@ -126,3 +136,25 @@ class Loss(Readable):
     def read_value(self):
         self.cap.read_value()
         return self.cap.loss
+
+
+class Freq(Writable):
+    cap = Attached()
+    value = Parameter('', FloatRange(unit='Hz'), default=0)
+
+    def initModule(self):
+        super().initModule()
+        self.cap.registerCallbacks(self, ['status'])  # auto update status
+
+    def update_value(self, _):
+        # value is always changed shortly after freq
+        self.value = self.cap.freq
+
+    @nopoll
+    def read_value(self):
+        self.cap.read_value()
+        return self.cap.freq
+
+    def write_target(self, target):
+        self.cap.write_freq(target)
+