improvements for flame

- frappy_psi.channelswitcher: use isBusy instead of checking value and target
- frappy_psi.ls372: remove underflow mechanism
- frappy_psi.parmod.SwitchDriv: switch the controlled module also when not buys

frappy_psi/channelswitcher.py

@@ -109,7 +109,7 @@ class ChannelSwitcher(Drivable):
 
     def read_status(self):
         now = time.monotonic()
-        if self.status[0] == 'BUSY':
+        if self.isBusy():
             chan = self.channels[self.target]
             if chan.is_switching(now, self._start_switch, self.switch_delay):
                 return self.status