heater: Support max_power setting for heaters

Change the mcu PWM value from an integer (0-255) to a float (0. - 1.).
Add support for limiting the maximum power (as measured over a
sufficiently long duration) to a particular heater.

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

1 files changed, 9 insertions, 2 deletions

diff --git a/config/example.cfg b/config/example.cfg
index 9f89d5e0..af418ca6 100644
--- a/config/example.cfg
+++ b/config/example.cfg
@@ -153,6 +153,13 @@ filament_diameter: 3.500
 heater_pin: ar4
 #   PWM output pin controlling the heater. This parameter must be
 #   provided.
+#max_power: 1.0
+#   The maximum power (expressed as a value from 0.0 to 1.0) that the
+#   heater_pin may be set to. The value 1.0 allows the pin to be set
+#   fully enabled for extended periods, while a value of 0.5 would
+#   allow the pin to be enabled for no more than half the time. This
+#   setting may be used to limit the total power output (over extended
+#   periods) to the heater. The default is 1.0.
 thermistor_pin: analog1
 #   Analog input pin connected to thermistor. This parameter must be
 #   provided.
@@ -179,9 +186,9 @@ pid_Kd: 114
 #   A time value (in seconds) over which the derivative in the pid
 #   will be smoothed to reduce the impact of measurement noise. The
 #   default is 2 seconds.
-#pid_integral_max: 255
+#pid_integral_max:
 #   The maximum "windup" the integral term may accumulate. The default
-#   is 255.
+#   is to use the same value as max_power.
 #min_extrude_temp: 170
 #   The minimum temperature (in Celsius) at which extruder move
 #   commands may be issued. The default is 170 Celsius.