delta: Add support for specifying the angle each tower is at

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

config/example-delta.cfg

@@ -18,6 +18,10 @@ step_distance: .01
 endstop_pin: ^ar2
 homing_speed: 50.0
 position_endstop: 297.05
+#angle:
+#   This option specifies the angle (in degrees) that the tower is
+#   at. The default is 210 for stepper_a, 330 for stepper_b, and 90
+#   for stepper_c.
 
 # The stepper_b section describes the stepper controlling the front
 # right tower (at 330 degrees).

klippy/delta.py

@@ -29,12 +29,13 @@ class DeltaKinematics:
         logging.info(
             "Delta max build height %.2fmm (radius tapered above %.2fmm)" % (
                 self.max_z, self.limit_z))
-        sin = lambda angle: math.sin(math.radians(angle))
-        cos = lambda angle: math.cos(math.radians(angle))
-        self.towers = [
-            (cos(210.)*radius, sin(210.)*radius),
-            (cos(330.)*radius, sin(330.)*radius),
-            (cos(90.)*radius, sin(90.)*radius)]
+        # Determine tower locations in cartesian space
+        angles = [config.getsection('stepper_a').getfloat('angle', 210.),
+                  config.getsection('stepper_b').getfloat('angle', 330.),
+                  config.getsection('stepper_c').getfloat('angle', 90.)]
+        self.towers = [(math.cos(math.radians(angle)) * radius,
+                        math.sin(math.radians(angle)) * radius)
+                       for angle in angles]
         # Find the point where an XY move could result in excessive
         # tower movement
         half_min_step_dist = min([s.step_dist for s in self.steppers]) * .5