class BarcodeReader(DeviceBase):

    def doInitialize(self):
        self.disable()
        self.readout = None
        self.processing = False
        self.task_callable=None
        
    def enable(self):
        microscan_cmd.write("<H>")
        self.setState(State.Ready)
    
    def disable(self):    
        microscan_cmd.write("<I>")
        self.setState(State.Disabled)
    
    def get(self,timeout=1.0):    
        self.state.assertReady()
        try:
            self.setState(State.Busy)
            microscan.flush()
            ret =  microscan.waitString(int(timeout * 1000)) 
            if ret is not None:
                ret = ret.strip()   
            self.setCache(ret, None)
            return ret
        except:
            self.setCache(None, None)
            return None
        finally:
            if self.state == State.Busy:
                self.setState(State.Ready)

    def doUpdate(self):
        self.get()


    def read(self,timeout=1.0):    
        if self.processing:
            raise Exception("Ongoing read operation")
        self.processing = True
        try:
            initial = self.state
            if initial == State.Disabled:
                self.enable()
            try:
                return self.get(timeout)
            finally:
                if initial == State.Disabled:
                    self.disable()
        finally:
            self.processing = False
    
    def _read_task(self, timeout):
        global readout
        self.readout = self.read(timeout)
        return self.readout
    
    def start_read(self, timeout=1.0):
        self.readout = None
        self.task_callable = fork((self._read_task, (timeout,)))   

    def get_readout(self):
        return self.readout

    def wait_readout(self):
        if self.task_callable is not None:
            join(self.task_callable)
            self.task_callable = None
        return self.readout


add_device(BarcodeReader("barcode_reader"), force = True)