hx71x: Load Cell Skeleton and HX71x bulk ADC

* Create the load_cell host module skeleton to create the sensors and start taking samples.
* Add support for the HX717 and HX711 ADC sensors.

Signed-off-by: Gareth Farrington <gareth@waves.ky>

klippy/extras/load_cell.py

@@ -0,0 +1,36 @@
+# Load Cell Implementation
+#
+# Copyright (C) 2024 Gareth Farrington <gareth@waves.ky>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+from . import hx71x
+
+# Printer class that controls a load cell
+class LoadCell:
+    def __init__(self, config, sensor):
+        self.printer = printer = config.get_printer()
+        self.sensor = sensor   # must implement BulkAdcSensor
+        # startup, when klippy is ready, start capturing data
+        printer.register_event_handler("klippy:ready", self._handle_ready)
+
+    def _handle_ready(self):
+        self.sensor.add_client(self._on_sample)
+
+    def _on_sample(self, msg):
+        return True
+
+    def get_sensor(self):
+        return self.sensor
+
+    def get_status(self, eventtime):
+        return {}
+
+def load_config(config):
+    # Sensor types
+    sensors = {}
+    sensors.update(hx71x.HX71X_SENSOR_TYPES)
+    sensor_class = config.getchoice('sensor_type', sensors)
+    return LoadCell(config, sensor_class(config))
+
+def load_config_prefix(config):
+    return load_config(config)