Initial commit: esphome-xtool-ap2 ESPHome component

Control one or two xTool SafetyPro AP2 air purifiers over BLE and expose them to Home Assistant via an ESP32 (the ap2_hub external component): per-slot fan control with live gear sync, runtime-settable flash-persisted MACs, an on-device scanner, M9033 status polling (filter life, serial, firmware), buzzer control, and BLE bonding. Includes the PC debug tool (tools/ap2_ble.py) and the reverse-engineered protocol spec (SPEC.md).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

components/ap2_hub/sensor.py

@@ -0,0 +1,38 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import sensor
+from esphome.const import UNIT_PERCENT
+
+from . import AP2Hub
+
+CONF_AP2_HUB_ID = "ap2_hub_id"
+CONF_SLOT = "slot"
+CONF_TYPE = "type"
+
+# Filter-life types -> index into AP2Filter (M9033 fields H I J K L S).
+FILTERS = {
+    "pre_filter": 0,
+    "medium_filter": 1,
+    "activated_carbon": 2,
+    "carbon_cloth": 3,
+    "formaldehyde": 4,
+    "hepa": 5,
+}
+
+CONFIG_SCHEMA = sensor.sensor_schema(
+    unit_of_measurement=UNIT_PERCENT,
+    accuracy_decimals=0,
+    icon="mdi:air-filter",
+).extend(
+    {
+        cv.GenerateID(CONF_AP2_HUB_ID): cv.use_id(AP2Hub),
+        cv.Required(CONF_SLOT): cv.int_range(min=0, max=1),
+        cv.Required(CONF_TYPE): cv.one_of(*FILTERS, lower=True),
+    }
+)
+
+
+async def to_code(config):
+    var = await sensor.new_sensor(config)
+    parent = await cg.get_variable(config[CONF_AP2_HUB_ID])
+    cg.add(parent.set_filter_sensor(config[CONF_SLOT], FILTERS[config[CONF_TYPE]], var))