display: Add initial support for LCD screens attached to an MCU

Add support for displaying basic status information on ST7920 and
HD44780 based LCDs that are attached directly to a micro-controller.

Signed-off-by: Marcio Teixeira <marcio@alephobjects.com>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/heater.py

@@ -197,6 +197,11 @@ class PrinterHeater:
         is_active = target_temp or last_temp > 50.
         return is_active, '%s: target=%.0f temp=%.1f pwm=%.3f' % (
             self.name, target_temp, last_temp, last_pwm_value)
+    def get_status(self, eventtime):
+        with self.lock:
+            target_temp = self.target_temp
+            last_temp = self.last_temp
+        return {'temperature': last_temp, 'target': target_temp}
 
 
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