From 520273e5abfd9a3dd899f94b5df602669b655ec0 Mon Sep 17 00:00:00 2001
From: Kevin O'Connor <kevin@koconnor.net>
Date: Mon, 29 Nov 2021 16:41:48 -0500
Subject: [PATCH] stepper: Support step_pulse_duration even on TMC drivers in
 UART/SPI mode

Commit 689231df changed the default step_pulse_duration to 100ns for
TMC drivers that are configured in UART/SPI mode, but it failed to
document that change in Config_Changes.md and Config_Reference.md.
Update those documents to reflect that change.

Update the code so that a user may specify a custom
step_pulse_duration even on TMC drivers that are configured in
UART/SPI mode.  This may be useful for drivers that use a level
shifter on the step pin that requires more than a ~300ns to detect a
level change.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
---
 docs/Config_Changes.md   | 7 ++++---
 docs/Config_Reference.md | 4 +++-
 klippy/stepper.py        | 5 ++++-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/docs/Config_Changes.md b/docs/Config_Changes.md
index e91ff465..11447d4d 100644
--- a/docs/Config_Changes.md
+++ b/docs/Config_Changes.md
@@ -16,9 +16,10 @@ use the older (typically less accurate) definition, define a custom
 `resistance1: 100000`, and `beta: 3950`.
 
 20211104: The "step pulse duration" option in "make menuconfig" has
-been removed. A new `step_pulse_duration` setting in the
-[stepper config section](Config_Reference.md#stepper) should be set
-for all steppers that need a custom pulse duration.
+been removed. The default step duration for TMC drivers configured in
+UART or SPI mode is now 100ns. A new `step_pulse_duration` setting in
+the [stepper config section](Config_Reference.md#stepper) should be
+set for all steppers that need a custom pulse duration.
 
 20211102: Several deprecated features have been removed.  The stepper
 `step_distance` option has been removed (deprecated on 20201222).  The
diff --git a/docs/Config_Reference.md b/docs/Config_Reference.md
index 67d8d036..36302664 100644
--- a/docs/Config_Reference.md
+++ b/docs/Config_Reference.md
@@ -157,7 +157,9 @@ microsteps:
 #   The minimum time between the step pulse signal edge and the
 #   following "unstep" signal edge. This is also used to set the
 #   minimum time between a step pulse and a direction change signal.
-#   The default is 0.000002 (which is 2us).
+#   The default is 0.000000100 (100ns) for TMC steppers that are
+#   configured in UART or SPI mode, and the default is 0.000002 (which
+#   is 2us) for all other steppers.
 endstop_pin:
 #   Endstop switch detection pin. If this endstop pin is on a
 #   different mcu than the stepper motor then it enables "multi-mcu
diff --git a/klippy/stepper.py b/klippy/stepper.py
index 2e6655ef..4a4f9ea4 100644
--- a/klippy/stepper.py
+++ b/klippy/stepper.py
@@ -14,6 +14,8 @@ class error(Exception):
 # Steppers
 ######################################################################
 
+MIN_BOTH_EDGE_DURATION = 0.000000200
+
 # Interface to low-level mcu and chelper code
 class MCU_stepper:
     def __init__(self, name, step_pin_params, dir_pin_params, step_dist,
@@ -70,7 +72,8 @@ class MCU_stepper:
             self._step_pulse_duration = .000002
         invert_step = self._invert_step
         sbe = int(self._mcu.get_constants().get('STEPPER_BOTH_EDGE', '0'))
-        if self._req_step_both_edge and sbe:
+        if (self._req_step_both_edge and sbe
+            and self._step_pulse_duration <= MIN_BOTH_EDGE_DURATION):
             # Enable stepper optimized step on both edges
             self._step_both_edge = True
             self._step_pulse_duration = 0.