endstop: Support oversampling of the endstop

Some printers can show occasional noise on the endstop pin.  Support
sampling the endstop pin multiple times to attempt to filter out this
noise.

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

klippy/mcu.py

@@ -137,6 +137,8 @@ class MCU_endstop:
         self._pin = pin_params['pin']
         self._pullup = pin_params['pullup']
         self._invert = pin_params['invert']
+        self._oversample_count = 0
+        self._oversample_time = 0.
         self._cmd_queue = mcu.alloc_command_queue()
         self._oid = self._home_cmd = self._query_cmd = None
         self._homing = False
@@ -144,6 +146,9 @@ class MCU_endstop:
         self._last_state = {}
     def get_mcu(self):
         return self._mcu
+    def setup_oversample(self, oversample_count, oversample_time):
+        self._oversample_count = oversample_count
+        self._oversample_time = oversample_time
     def add_stepper(self, stepper):
         self._steppers.append(stepper)
     def build_config(self):
@@ -155,6 +160,10 @@ class MCU_endstop:
             self._mcu.add_config_cmd(
                 "end_stop_set_stepper oid=%d pos=%d stepper_oid=%d" % (
                     self._oid, i, s.get_oid()), is_init=True)
+        self._mcu.add_config_cmd(
+            "end_stop_set_oversample oid=%d sample_ticks=%d sample_count=%d" % (
+                self._oid, self._mcu.seconds_to_clock(self._oversample_time),
+                self._oversample_count), is_init=True)
         self._home_cmd = self._mcu.lookup_command(
             "end_stop_home oid=%c clock=%u rest_ticks=%u pin_value=%c")
         self._query_cmd = self._mcu.lookup_command("end_stop_query oid=%c")

klippy/stepper.py

@@ -6,6 +6,9 @@
 import math, logging
 import homing, pins
 
+ENDSTOP_OVERSAMPLE_COUNT = 4
+ENDSTOP_OVERSAMPLE_TIME = .000015
+
 class PrinterStepper:
     def __init__(self, printer, config, name):
         self.name = name
@@ -52,6 +55,8 @@ class PrinterHomingStepper(PrinterStepper):
 
         self.mcu_endstop = pins.setup_pin(
             printer, 'endstop', config.get('endstop_pin'))
+        self.mcu_endstop.setup_oversample(
+            ENDSTOP_OVERSAMPLE_COUNT, ENDSTOP_OVERSAMPLE_TIME)
         self.mcu_endstop.add_stepper(self.mcu_stepper)
         self.position_min = config.getfloat('position_min', 0.)
         self.position_max = config.getfloat(

src/endstop.c

@@ -13,9 +13,9 @@
 
 struct end_stop {
     struct timer time;
-    uint32_t rest_time;
+    uint32_t rest_time, sample_time;
     struct gpio_in pin;
-    uint8_t flags, stepper_count;
+    uint8_t flags, stepper_count, sample_count, trigger_count;
     struct stepper *steppers[0];
 };
 
@@ -34,6 +34,8 @@ stop_steppers(struct end_stop *e)
     sched_wake_task(&endstop_wake);
 }
 
+static uint_fast8_t end_stop_oversample_event(struct timer *t);
+
 // Timer callback for an end stop
 static uint_fast8_t
 end_stop_event(struct timer *t)
@@ -45,8 +47,32 @@ end_stop_event(struct timer *t)
         e->time.waketime += e->rest_time;
         return SF_RESCHEDULE;
     }
-    stop_steppers(e);
-    return SF_DONE;
+    e->time.func = end_stop_oversample_event;
+    return end_stop_oversample_event(t);
+}
+
+// Timer callback for an end stop this is sampling extra times
+static uint_fast8_t
+end_stop_oversample_event(struct timer *t)
+{
+    struct end_stop *e = container_of(t, struct end_stop, time);
+    uint8_t val = gpio_in_read(e->pin);
+    if ((val ? ~e->flags : e->flags) & ESF_PIN_HIGH) {
+        // No longer matching - reschedule for the next attempt
+        e->time.func = end_stop_event;
+        uint8_t past_triggers = e->sample_count - e->trigger_count;
+        e->time.waketime += e->rest_time - past_triggers * e->sample_time;
+        e->trigger_count = e->sample_count;
+        return SF_RESCHEDULE;
+    }
+    uint8_t count = e->trigger_count - 1;
+    if (!count) {
+        stop_steppers(e);
+        return SF_DONE;
+    }
+    e->trigger_count = count;
+    e->time.waketime += e->sample_time;
+    return SF_RESCHEDULE;
 }
 
 void
@@ -56,9 +82,9 @@ command_config_end_stop(uint32_t *args)
     struct end_stop *e = oid_alloc(
         args[0], command_config_end_stop
         , sizeof(*e) + sizeof(e->steppers[0]) * stepper_count);
-    e->time.func = end_stop_event;
     e->pin = gpio_in_setup(args[1], args[2]);
     e->stepper_count = stepper_count;
+    e->sample_count = 1;
 }
 DECL_COMMAND(command_config_end_stop,
              "config_end_stop oid=%c pin=%c pull_up=%c stepper_count=%c");
@@ -75,6 +101,18 @@ command_end_stop_set_stepper(uint32_t *args)
 DECL_COMMAND(command_end_stop_set_stepper,
              "end_stop_set_stepper oid=%c pos=%c stepper_oid=%c");
 
+void
+command_end_stop_set_oversample(uint32_t *args)
+{
+    struct end_stop *e = oid_lookup(args[0], command_config_end_stop);
+    e->sample_time = args[1];
+    e->sample_count = args[2];
+    if (!e->sample_count)
+        e->sample_count = 1;
+}
+DECL_COMMAND(command_end_stop_set_oversample,
+             "end_stop_set_oversample oid=%c sample_ticks=%u sample_count=%c");
+
 // Home an axis
 void
 command_end_stop_home(uint32_t *args)
@@ -88,6 +126,8 @@ command_end_stop_home(uint32_t *args)
         e->flags = 0;
         return;
     }
+    e->time.func = end_stop_event;
+    e->trigger_count = e->sample_count;
     e->flags = ESF_HOMING | (args[3] ? ESF_PIN_HIGH : 0);
     sched_add_timer(&e->time);
 }