heaters: add last pwm value to heater.get_status (#3621)

Signed-off-by: Stefan Dej <meteyou@gmail.com>

docs/Command_Templates.md

@@ -166,6 +166,8 @@ The following are common printer attributes:
   <config_name>`.
 - `printer.<heater>.target`: The current target temperature (in
   Celsius as a float) for the given heater.
+- `printer.<heater>.power`: The last setting of the PWM pin (a value
+  between 0.0 and 1.0) associated with the heater.
 - `printer.idle_timeout.state`: The current state of the printer as
   tracked by the idle_timeout module. It is one of the following
   strings: "Idle", "Printing", "Ready".

klippy/extras/heaters.py

@@ -135,7 +135,9 @@ class Heater:
         with self.lock:
             target_temp = self.target_temp
             smoothed_temp = self.smoothed_temp
-        return {'temperature': smoothed_temp, 'target': target_temp}
+            last_pwm_value = self.last_pwm_value
+        return {'temperature': smoothed_temp, 'target': target_temp,
+                'power': last_pwm_value}
     cmd_SET_HEATER_TEMPERATURE_help = "Sets a heater temperature"
     def cmd_SET_HEATER_TEMPERATURE(self, gcmd):
         temp = gcmd.get_float('TARGET', 0.)