diff --git a/GCode_Interpreterdc.py b/GCode_Interpreterdc.py
index ccba089..dd71097 100644
--- a/GCode_Interpreterdc.py
+++ b/GCode_Interpreterdc.py
@@ -259,6 +259,92 @@ class GCodeToMotors:
                             self.feedrate_micros = self.get_max_speed()
                     self.move(self.feedrate_micros)
 
+                case 2, 3:
+                    center = [0., 0., 0.]
+                    center[0] = search_string('I', instruction) + self.current_units[0]
+                    center[1] = search_string('J', instruction) + self.current_units[1]
+
+                    aX = self.current_units[0] - center[0]
+                    aY = self.current_units[1] - center[1]
+                    bX = fp[0] - center[0]
+                    bY = fp[1] - center[1]
+
+                    if code == 2:  # If in fucked up anti-trigonometric direction
+                        angleA = np.atan2(bY, bX)
+                        angleB = np.atan2(aY, aX)
+                    else:
+                        angleA = np.atan2(aY, aX)
+                        angleB = np.atan2(bY, bX)
+
+                    if angleB <= angleA:
+                        angleB += 2 * np.pi
+                    angle = angleB - angleA
+
+                    radius = np.linalg.norm([aX, aY])
+                    length = radius * angle
+                    steps = np.ceil(length/self.curve_section)
+
+                    newPoint = [0., 0., 0.]
+                    for step in range(1, steps + 1):
+                        step = step if (code == 3) else steps - step
+                        newPoint[0] = center[0] + radius * np.cos(angleA + angle * (step / steps))
+                        newPoint[1] = center[1] + radius * np.sin(angleA + angle * (step / steps))
+                        self.set_position(newPoint[0], newPoint[1], fp[2])
+
+                        if self.feedrate > 0:
+                            self.feedrate_micros = self.calculate_feedrate_delay(self.feedrate)
+                        else:
+                            self.feedrate_micros = self.get_max_speed()
+
+                        self.move(self.feedrate_micros)
+
+                case 4:
+                    time.sleep(search_string('P', instruction) * 1e-3)
+
+                case 20:
+                    self.x_units = self.X_STEPS_PER_INCH
+                    self.y_units = self.Y_STEPS_PER_INCH
+                    self.z_units = self.Z_STEPS_PER_INCH
+                    self.curve_section = self.CURVE_SECTION_INCHES
+
+                    self.calculate_deltas()
+
+                case 21:
+                    self.x_units = self.X_STEPS_PER_MM
+                    self.y_units = self.Y_STEPS_PER_MM
+                    self.z_units = self.Z_STEPS_PER_MM
+                    self.curve_section = self.CURVE_SECTION_MM
+
+                    self.calculate_deltas()
+
+                case 28:
+                    self.set_target(0., 0., 0.)
+                    self.move(self.get_max_speed())
+
+                case 30:
+                    fp = [0., 0., 0.]
+                    fp[0] = search_string('X', instruction)
+                    fp[1] = search_string('Y', instruction)
+                    fp[2] = search_string('Z', instruction)
+
+                    if self.abs_mode:
+                        if not has_command('X', instruction):
+                            fp[0] = self.current_units[0]
+                        if not has_command('Y', instruction):
+                            fp[1] = self.current_units[1]
+                        if not has_command('Z', instruction):
+                            fp[2] = self.current_units[2]
+
+                        self.set_target(fp[0], fp[1], fp[2])
+                    else:
+                        self.set_target(self.current_units[0] + fp[0], self.current_units[1] + fp[1], self.current_units[2] + fp[2])
+
+                    self.move(self.get_max_speed())
+                    self.set_target(0., 0., 0.)
+                    self.move(self.get_max_speed())
+
+
+
         return
 
     def execute(self, gcode):