fan: add enable_pin option (#5732)

Signed-off-by: Lasse Dalegaard <dalegaard@gmail.com>

2 files changed, 21 insertions, 0 deletions

diff --git a/docs/Config_Reference.md b/docs/Config_Reference.md
index 833e14570..90bf1770f 100644
--- a/docs/Config_Reference.md
+++ b/docs/Config_Reference.md
@@ -2520,6 +2520,12 @@ pin:
 #   enough for fans below 10000 RPM at 2 PPR. This must be smaller than
 #   30/(tachometer_ppr*rpm), with some margin, where rpm is the
 #   maximum speed (in RPM) of the fan.
+#enable_pin:
+#   Optional pin to enable power to the fan. This can be useful for fans
+#   with dedicated PWM inputs. Some of these fans stay on even at 0% PWM
+#   input. In such a case, the PWM pin can be used normally, and e.g. a
+#   ground-switched FET(standard fan pin) can be used to control power to
+#   the fan.
 ```
 
 ### [heater_fan]
@@ -2541,6 +2547,7 @@ a shutdown_speed equal to max_power.
 #tachometer_pin:
 #tachometer_ppr:
 #tachometer_poll_interval:
+#enable_pin:
 #   See the "fan" section for a description of the above parameters.
 #heater: extruder
 #   Name of the config section defining the heater that this fan is
@@ -2577,6 +2584,7 @@ watched component.
 #tachometer_pin:
 #tachometer_ppr:
 #tachometer_poll_interval:
+#enable_pin:
 #   See the "fan" section for a description of the above parameters.
 #fan_speed: 1.0
 #   The fan speed (expressed as a value from 0.0 to 1.0) that the fan
@@ -2622,6 +2630,7 @@ information.
 #tachometer_pin:
 #tachometer_ppr:
 #tachometer_poll_interval:
+#enable_pin:
 #   See the "fan" section for a description of the above parameters.
 #sensor_type:
 #sensor_pin:
@@ -2679,6 +2688,7 @@ with the SET_FAN_SPEED [gcode command](G-Codes.md#fan_generic).
 #tachometer_pin:
 #tachometer_ppr:
 #tachometer_poll_interval:
+#enable_pin:
 #   See the "fan" section for a description of the above parameters.
 ```
 
diff --git a/klippy/extras/fan.py b/klippy/extras/fan.py
index 77fdef8a3..d6e687218 100644
--- a/klippy/extras/fan.py
+++ b/klippy/extras/fan.py
@@ -30,6 +30,12 @@ class Fan:
         shutdown_power = max(0., min(self.max_power, shutdown_speed))
         self.mcu_fan.setup_start_value(0., shutdown_power)
 
+        self.enable_pin = None
+        enable_pin = config.get('enable_pin', None)
+        if enable_pin is not None:
+            self.enable_pin = ppins.setup_pin('digital_out', enable_pin)
+            self.enable_pin.setup_max_duration(0.)
+
         # Setup tachometer
         self.tachometer = FanTachometer(config)
 
@@ -46,6 +52,11 @@ class Fan:
         if value == self.last_fan_value:
             return
         print_time = max(self.last_fan_time + FAN_MIN_TIME, print_time)
+        if self.enable_pin:
+            if value > 0 and self.last_fan_value == 0:
+                self.enable_pin.set_digital(print_time, 1)
+            elif value == 0 and self.last_fan_value > 0:
+                self.enable_pin.set_digital(print_time, 0)
         if (value and value < self.max_power and self.kick_start_time
             and (not self.last_fan_value or value - self.last_fan_value > .5)):
             # Run fan at full speed for specified kick_start_time