power on warning

elkplot/device.py

@@ -302,3 +302,8 @@ def pen_up(self):
     def pen_down(self):
         """Lower the pen"""
         return self._command("SP", 0, self.pen_down_delay, self.pen_lift_pin)
+
+    def powered_on(self):
+        stepper, motor = (int(elem) for elem in self._command("QC").split(","))
+        self._readline()
+        return stepper > 200 and motor > 200

elkplot/util.py

@@ -85,10 +85,13 @@ def draw(
             f"Drawing has bounds ({min_x}, {min_y}) to ({max_x}, {max_y}), which extends outside the plottable bounds (0, 0) to ({width}, {height})"
         )
     if not elkplot.device.axidraw_available():
-        raise AxidrawNotFoundError()
+        raise AxidrawNotFoundError("Unable to communicate with device. Is the USB cable plugged in?")
     device = elkplot.Device() if device is None else device
+    if not device.powered_on():
+        raise AxidrawNotFoundError("Motors do not have power. Is the AxiDraw plugged in and turned on?")
     device.zero_position()
     device.enable_motors()
+    device.pen_up()
     for layer, label in zip(layers, layer_labels):
         input(f"Press enter when you're ready to draw {label}")
         for _ in range(retrace):