stepper: Add get/set_tag_position() and convert calc_position()

Rename calc_position() to calc_tag_position() and have it calculate
the value of the position from the last stepper set_tag_position()
call.  This enables the calc_tag_position() code to be more flexible
as it can be run with arbitrary positions.

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

1 files changed, 6 insertions, 5 deletions

diff --git a/docs/Code_Overview.md b/docs/Code_Overview.md
index 22bbf2d3..7f4be890 100644
--- a/docs/Code_Overview.md
+++ b/docs/Code_Overview.md
@@ -330,11 +330,12 @@ Useful steps:
    seconds) to a cartesian coordinate (in millimeters), and then
    calculate the desired stepper position (in millimeters) from that
    cartesian coordinate.
-4. Implement the `calc_position()` method in the new kinematics class.
-   This method calculates the position of the toolhead in cartesian
-   coordinates from the current position of each stepper. It does not
-   need to be efficient as it is typically only called during homing
-   and probing operations.
+4. Implement the `calc_tag_position()` method in the new kinematics
+   class. This method calculates the position of the toolhead in
+   cartesian coordinates from the position of each stepper (as
+   returned by `stepper.get_tag_position()`). It does not need to be
+   efficient as it is typically only called during homing and probing
+   operations.
 5. Other methods. Implement the `check_move()`, `get_status()`,
    `get_steppers()`, `home()`, and `set_position()` methods. These
    functions are typically used to provide kinematic specific