stepper: Automatically detect and handle shared stepper enable lines

It's common for multiple steppers to use the same stepper enable
line.  Detect this and only create a single digital_out oid on the
micro-controller.

Also, prohibit any other pin from being used multiple times in the
config file.

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

docs/Todo.md

@@ -71,8 +71,6 @@ Hardware features
 
 * Support for additional kinematics: scara, etc.
 
-* Support shared motor enable GPIO lines.
-
 * Support for bed-level probes.
 
 * Possible support for touch panels attached to the micro-controller.

klippy/pins.py

@@ -1,6 +1,6 @@
 # Pin name to pin number definitions
 #
-# Copyright (C) 2016,2017  Kevin O'Connor <kevin@koconnor.net>
+# Copyright (C) 2016-2018  Kevin O'Connor <kevin@koconnor.net>
 #
 # This file may be distributed under the terms of the GNU GPLv3 license.
 import re
@@ -180,7 +180,8 @@ class PrinterPins:
     error = error
     def __init__(self):
         self.chips = {}
-    def lookup_pin(self, pin_type, pin_desc):
+        self.active_pins = {}
+    def lookup_pin(self, pin_type, pin_desc, share_type=None):
         can_invert = pin_type in ['stepper', 'endstop', 'digital_out', 'pwm']
         can_pullup = pin_type == 'endstop'
         pullup = invert = 0
@@ -196,8 +197,19 @@ class PrinterPins:
             chip_name, pin = [s.strip() for s in pin_desc.split(':', 1)]
         if chip_name not in self.chips:
             raise error("Unknown pin chip name '%s'" % (chip_name,))
-        return {'chip': self.chips[chip_name], 'chip_name': chip_name,
+        share_name = "%s:%s" % (chip_name, pin)
-                'type': pin_type, 'pin': pin, 'invert': invert, 'pullup': pullup}
+        if share_name in self.active_pins:
+            pin_params = self.active_pins[share_name]
+            if share_type is None or share_type != pin_params['share_type']:
+                raise error("pin %s used multiple times in config" % (pin,))
+            if invert != pin_params['invert'] or pullup != pin_params['pullup']:
+                raise error("Shared pin %s must have same polarity" % (pin,))
+            return pin_params
+        pin_params = {'chip': self.chips[chip_name], 'chip_name': chip_name,
+                      'type': pin_type, 'share_type': share_type,
+                      'pin': pin, 'invert': invert, 'pullup': pullup}
+        self.active_pins[share_name] = pin_params
+        return pin_params
     def setup_pin(self, pin_type, pin_desc):
         pin_params = self.lookup_pin(pin_type, pin_desc)
         return pin_params['chip'].setup_pin(pin_params)

klippy/stepper.py

@@ -1,11 +1,38 @@
 # Printer stepper support
 #
-# Copyright (C) 2016,2017  Kevin O'Connor <kevin@koconnor.net>
+# Copyright (C) 2016-2018  Kevin O'Connor <kevin@koconnor.net>
 #
 # This file may be distributed under the terms of the GNU GPLv3 license.
 import math, logging
 import homing, pins
 
+# Tracking of shared stepper enable pins
+class StepperEnablePin:
+    def __init__(self, mcu_enable, enable_count=0):
+        self.mcu_enable = mcu_enable
+        self.enable_count = enable_count
+    def set_enable(self, print_time, enable):
+        if enable:
+            if not self.enable_count:
+                self.mcu_enable.set_digital(print_time, 1)
+            self.enable_count += 1
+        else:
+            self.enable_count -= 1
+            if not self.enable_count:
+                self.mcu_enable.set_digital(print_time, 0)
+
+def lookup_enable_pin(printer, pin):
+    if pin is None:
+        return StepperEnablePin(None, 9999)
+    pin_params = pins.get_printer_pins(printer).lookup_pin(
+        'digital_out', pin, 'stepper_enable')
+    enable = pin_params.get('class')
+    if enable is None:
+        mcu_enable = pin_params['chip'].setup_pin(pin_params)
+        mcu_enable.setup_max_duration(0.)
+        pin_params['class'] = enable = StepperEnablePin(mcu_enable)
+    return enable
+
 # Code storing the definitions for a stepper motor
 class PrinterStepper:
     def __init__(self, printer, config):
@@ -23,12 +50,7 @@ class PrinterStepper:
         self.mcu_stepper.setup_step_distance(self.step_dist)
         self.step_const = self.mcu_stepper.step_const
         self.step_delta = self.mcu_stepper.step_delta
-        # Enable pin
+        self.enable = lookup_enable_pin(printer, config.get('enable_pin', None))
-        enable_pin = config.get('enable_pin', None)
-        self.mcu_enable = None
-        if enable_pin is not None:
-            self.mcu_enable = pins.setup_pin(printer, 'digital_out', enable_pin)
-            self.mcu_enable.setup_max_duration(0.)
     def _dist_to_time(self, dist, start_velocity, accel):
         # Calculate the time it takes to travel a distance with constant accel
         time_offset = start_velocity / accel
@@ -44,9 +66,8 @@ class PrinterStepper:
     def set_position(self, pos):
         self.mcu_stepper.set_position(pos)
     def motor_enable(self, print_time, enable=0):
-        if (self.mcu_enable is not None
+        if self.need_motor_enable != (not enable):
-            and self.need_motor_enable != (not enable)):
+            self.enable.set_enable(print_time, enable)
-            self.mcu_enable.set_digital(print_time, enable)
         self.need_motor_enable = not enable
 
 # Support for stepper controlled linear axis with an endstop