pwm_tool: Add support for high-speed PWM pin updates

The output_pin module is only capable of updating an output pin at
most once every 100ms.  Add a new pwm_tool module that is capable of
queuing updates in the micro-controller and thus allowing for much
higher update rates.

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

1 files changed, 157 insertions, 0 deletions

diff --git a/klippy/extras/pwm_tool.py b/klippy/extras/pwm_tool.py
new file mode 100644
index 00000000..c012bb31
--- /dev/null
+++ b/klippy/extras/pwm_tool.py
@@ -0,0 +1,157 @@
+# Queued PWM gpio output
+#
+# Copyright (C) 2017-2023  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import chelper
+
+PIN_MIN_TIME = 0.100
+MAX_SCHEDULE_TIME = 5.0
+
+class error(Exception):
+    pass
+
+class MCU_queued_pwm:
+    def __init__(self, pin_params):
+        self._mcu = pin_params['chip']
+        self._hardware_pwm = False
+        self._cycle_time = 0.100
+        self._max_duration = 2.
+        self._oid = self._mcu.create_oid()
+        ffi_main, ffi_lib = chelper.get_ffi()
+        self._stepqueue = ffi_main.gc(ffi_lib.stepcompress_alloc(self._oid),
+                                      ffi_lib.stepcompress_free)
+        self._mcu.register_stepqueue(self._stepqueue)
+        self._stepcompress_queue_mq_msg = ffi_lib.stepcompress_queue_mq_msg
+        self._mcu.register_config_callback(self._build_config)
+        self._pin = pin_params['pin']
+        self._invert = pin_params['invert']
+        self._start_value = self._shutdown_value = float(self._invert)
+        self._last_clock = self._cycle_ticks = 0
+        self._pwm_max = 0.
+        self._set_cmd_tag = None
+    def get_mcu(self):
+        return self._mcu
+    def setup_max_duration(self, max_duration):
+        self._max_duration = max_duration
+    def setup_cycle_time(self, cycle_time, hardware_pwm=False):
+        self._cycle_time = cycle_time
+        self._hardware_pwm = hardware_pwm
+    def setup_start_value(self, start_value, shutdown_value):
+        if self._invert:
+            start_value = 1. - start_value
+            shutdown_value = 1. - shutdown_value
+        self._start_value = max(0., min(1., start_value))
+        self._shutdown_value = max(0., min(1., shutdown_value))
+    def _build_config(self):
+        if self._max_duration and self._start_value != self._shutdown_value:
+            raise pins.error("Pin with max duration must have start"
+                             " value equal to shutdown value")
+        cmd_queue = self._mcu.alloc_command_queue()
+        curtime = self._mcu.get_printer().get_reactor().monotonic()
+        printtime = self._mcu.estimated_print_time(curtime)
+        self._last_clock = self._mcu.print_time_to_clock(printtime + 0.200)
+        cycle_ticks = self._mcu.seconds_to_clock(self._cycle_time)
+        mdur_ticks = self._mcu.seconds_to_clock(self._max_duration)
+        if mdur_ticks >= 1<<31:
+            raise pins.error("PWM pin max duration too large")
+        if self._hardware_pwm:
+            self._pwm_max = self._mcu.get_constant_float("PWM_MAX")
+            self._mcu.add_config_cmd(
+                "config_pwm_out oid=%d pin=%s cycle_ticks=%d value=%d"
+                " default_value=%d max_duration=%d"
+                % (self._oid, self._pin, cycle_ticks,
+                   self._start_value * self._pwm_max,
+                   self._shutdown_value * self._pwm_max, mdur_ticks))
+            svalue = int(self._start_value * self._pwm_max + 0.5)
+            self._mcu.add_config_cmd("queue_pwm_out oid=%d clock=%d value=%d"
+                                     % (self._oid, self._last_clock, svalue),
+                                     on_restart=True)
+            self._set_cmd_tag = self._mcu.lookup_command(
+                "queue_pwm_out oid=%c clock=%u value=%hu",
+                cq=cmd_queue).get_command_tag()
+            return
+        # Software PWM
+        if self._shutdown_value not in [0., 1.]:
+            raise pins.error("shutdown value must be 0.0 or 1.0 on soft pwm")
+        if cycle_ticks >= 1<<31:
+            raise pins.error("PWM pin cycle time too large")
+        self._mcu.add_config_cmd(
+            "config_digital_out oid=%d pin=%s value=%d"
+            " default_value=%d max_duration=%d"
+            % (self._oid, self._pin, self._start_value >= 1.0,
+               self._shutdown_value >= 0.5, mdur_ticks))
+        self._mcu.add_config_cmd(
+            "set_digital_out_pwm_cycle oid=%d cycle_ticks=%d"
+            % (self._oid, cycle_ticks))
+        self._cycle_ticks = cycle_ticks
+        svalue = int(self._start_value * cycle_ticks + 0.5)
+        self._mcu.add_config_cmd(
+            "queue_digital_out oid=%d clock=%d on_ticks=%d"
+            % (self._oid, self._last_clock, svalue), is_init=True)
+        self._set_cmd_tag = self._mcu.lookup_command(
+            "queue_digital_out oid=%c clock=%u on_ticks=%u",
+            cq=cmd_queue).get_command_tag()
+    def set_pwm(self, print_time, value):
+        clock = self._mcu.print_time_to_clock(print_time)
+        minclock = self._last_clock
+        self._last_clock = clock
+        if self._invert:
+            value = 1. - value
+        max_count = self._cycle_ticks
+        if self._hardware_pwm:
+            max_count = self._pwm_max
+        v = int(max(0., min(1., value)) * max_count + 0.5)
+        data = (self._set_cmd_tag, self._oid, clock & 0xffffffff, v)
+        ret = self._stepcompress_queue_mq_msg(self._stepqueue, clock,
+                                              data, len(data))
+        if ret:
+            raise error("Internal error in stepcompress")
+
+class PrinterOutputPin:
+    def __init__(self, config):
+        self.printer = config.get_printer()
+        ppins = self.printer.lookup_object('pins')
+        # Determine pin type
+        pin_params = ppins.lookup_pin(config.get('pin'), can_invert=True)
+        self.mcu_pin = MCU_queued_pwm(pin_params)
+        cycle_time = config.getfloat('cycle_time', 0.100, above=0.,
+                                     maxval=MAX_SCHEDULE_TIME)
+        hardware_pwm = config.getboolean('hardware_pwm', False)
+        self.mcu_pin.setup_cycle_time(cycle_time, hardware_pwm)
+        self.scale = config.getfloat('scale', 1., above=0.)
+        self.last_print_time = 0.
+        self.mcu_pin.setup_max_duration(0.)
+        # Determine start and shutdown values
+        self.last_value = config.getfloat(
+            'value', 0., minval=0., maxval=self.scale) / self.scale
+        self.shutdown_value = config.getfloat(
+            'shutdown_value', 0., minval=0., maxval=self.scale) / self.scale
+        self.mcu_pin.setup_start_value(self.last_value, self.shutdown_value)
+        # Register commands
+        pin_name = config.get_name().split()[1]
+        gcode = self.printer.lookup_object('gcode')
+        gcode.register_mux_command("SET_PIN", "PIN", pin_name,
+                                   self.cmd_SET_PIN,
+                                   desc=self.cmd_SET_PIN_help)
+    def get_status(self, eventtime):
+        return {'value': self.last_value}
+    def _set_pin(self, print_time, value):
+        if value == self.last_value:
+            return
+        print_time = max(print_time, self.last_print_time)
+        self.mcu_pin.set_pwm(print_time, value)
+        self.last_value = value
+        self.last_print_time = print_time
+    cmd_SET_PIN_help = "Set the value of an output pin"
+    def cmd_SET_PIN(self, gcmd):
+        # Read requested value
+        value = gcmd.get_float('VALUE', minval=0., maxval=self.scale)
+        value /= self.scale
+        # Obtain print_time and apply requested settings
+        toolhead = self.printer.lookup_object('toolhead')
+        toolhead.register_lookahead_callback(
+            lambda print_time: self._set_pin(print_time, value))
+
+def load_config_prefix(config):
+    return PrinterOutputPin(config)