fan: Add tachometer support

This adds new config options for fans:  'tachometer_pin' to specify the
GPIO pin, and 'tachometer_ppr' (default 2) to specify the number of
signal pulses per revolution.  The rpm is also exposed by get_status for
command templates and the API server.  For fast fans (at least 10000
RPM), the polling interval can be shortened using the
'tachometer_poll_interval' option.

There is a new mcu object for a generic edge counter, which repeatedly
polls a GPIO pin and periodically reports the count to the host.

Signed-off-by: Adrian Keet <arkeet@gmail.com>

klippy/extras/pulse_counter.py

@@ -0,0 +1,79 @@
+# Support for GPIO input edge counters
+#
+# Copyright (C) 2021  Adrian Keet <arkeet@gmail.com>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+
+class MCU_counter:
+    def __init__(self, printer, pin, sample_time, poll_time):
+        ppins = printer.lookup_object('pins')
+        pin_params = ppins.lookup_pin(pin, can_pullup=True)
+        self._mcu = pin_params['chip']
+        self._oid = self._mcu.create_oid()
+        self._pin = pin_params['pin']
+        self._pullup = pin_params['pullup']
+        self._poll_time = poll_time
+        self._sample_time = sample_time
+        self._callback = None
+        self._last_count = 0
+        self._mcu.register_config_callback(self.build_config)
+
+    def build_config(self):
+        self._mcu.add_config_cmd("config_counter oid=%d pin=%s pull_up=%d"
+            % (self._oid, self._pin, self._pullup))
+        clock = self._mcu.get_query_slot(self._oid)
+        poll_ticks = self._mcu.seconds_to_clock(self._poll_time)
+        sample_ticks = self._mcu.seconds_to_clock(self._sample_time)
+        self._mcu.add_config_cmd(
+            "query_counter oid=%d clock=%d poll_ticks=%d sample_ticks=%d"
+            % (self._oid, clock, poll_ticks, sample_ticks), is_init=True)
+        self._mcu.register_response(self._handle_counter_state,
+                                    "counter_state", self._oid)
+
+    # Callback is called periodically every sample_time
+    def setup_callback(self, cb):
+        self._callback = cb
+
+    def _handle_counter_state(self, params):
+        clock = self._mcu.clock32_to_clock64(params['time'])
+        time = self._mcu.clock_to_print_time(clock)
+
+        count_clock = self._mcu.clock32_to_clock64(params['count_time'])
+        count_time = self._mcu.clock_to_print_time(count_clock)
+
+        # handle 32-bit counter overflow
+        last_count = self._last_count
+        delta_count = (params['count'] - last_count) & 0xffffffff
+        count = last_count + delta_count
+        self._last_count = count
+
+        if self._callback is not None:
+            self._callback(time, count, count_time)
+
+class FrequencyCounter:
+    def __init__(self, printer, pin, sample_time, poll_time):
+        self._callback = None
+        self._last_time = self._last_count = None
+        self._freq = 0.
+        self._counter = MCU_counter(printer, pin, sample_time, poll_time)
+        self._counter.setup_callback(self._counter_callback)
+
+    def _counter_callback(self, time, count, count_time):
+        if self._last_time is None:  # First sample
+            self._last_time = time
+        else:
+            delta_time = count_time - self._last_time
+            if delta_time > 0:
+                self._last_time = count_time
+                delta_count = count - self._last_count
+                self._freq = delta_count / delta_time
+            else:  # No counts since last sample
+                self._last_time = time
+                self._freq = 0.
+            if self._callback is not None:
+                self._callback(time, self._freq)
+        self._last_count = count
+
+    @property
+    def frequency(self):
+        return self._freq