import ch.psi.pshell.device.Speedable as Speedable


class PseudoMotor(RegisterBase, Speedable):    
    def __init__(self, name):
        RegisterBase.__init__(self, name)
        self.readback  = 0.0
        self.setpoint  = 0.0
        self.settime = time.time()
        
    def doRead(self):     
         offset = self.setpoint - self.readback
         d = (self.speed * (time.time() - self.settime))
         d = min(d, abs(offset))         
         self.readback = self.readback + d if offset>0 else self.readback -d
         self.settime = time.time()
         return self.readback

    def doWrite(self, val):
        self.settime = time.time()
        self.setpoint = val

    def getSpeed(self):
        return 3.0
        
positioner =  PseudoMotor("PseudoMotor")       
add_device(positioner, True);

cscan(positioner, MachineCurrent, 0, 10, 1.0)