Create bthome.py

Author: DavesCodeMusings

bthome.py

@@ -0,0 +1,101 @@
+# BTHome MicroPython
+# Construct Bluetooth Low Energy (BLE) advertising payloads for BTHome v2.
+# See https://bthome.io/ for more information about BTHome.
+# See https://github.com/DavesCodeMusings/BTHome-MicroPython for more about this module.
+
+from micropython import const
+from struct import pack
+
+# See "Advertising Payload" at https://bthome.io/format/ for details.
+_ADVERT_LENGTH_MAX = const(255)
+_ADVERT_FLAGS = bytes.fromhex('020106')  # length (02), flags indicator (01), flag bits (06)
+_DEVICE_NAME_LENGTH_MAX = const(10)
+_SERVICE_DATA_UUID16 = const(0x16)
+_SERVICE_UUID16 = const(0xFCD2)   # See: https://bthome.io/images/License_Statement_-_BTHOME.pdf
+_DEVICE_INFO_FLAGS = const(0x40)  # Currently hardcoded: no encryption, regular updates, version 2
+
+# See "Sensor Data" table at https://bthome.io/format/ for details.
+BATTERY_UINT8 = const(0x01)
+TEMPERATURE_SINT16 = const(0x02)
+_TEMPERATURE_SINT16_SCALING = const(100)
+HUMIDITY_UINT16 = const(0x03)
+_HUMIDITY_UINT16_SCALING = const(100)
+PRESSURE_UINT24 = const(0x04)
+_PRESSURE_UINT24_SCALING = const(100)
+ILLUMINANCE_UINT24 = const(0x05)
+_ILLUMINANCE_UINT24_SCALING = const(100)
+
+# Default value decimal places indicate precision
+device_name = "BTHome-MPY"
+battery = 0         # percent
+temperature = 0.00  # degrees Celsius
+humidity = 0.00     # percent (relative humidity)
+pressure = 0.00     # hectoPascals (millibars)
+illuminance = 0.0   # Lux
+
+def _pack_device_name():
+    assert len(device_name) > 0
+    assert len(device_name) <= _DEVICE_NAME_LENGTH_MAX
+    name_type = bytes.fromhex('09')  # indicator for complete name
+    device_name_bytes = name_type + device_name.encode()
+    device_name_bytes = bytes([len(device_name_bytes)]) + device_name_bytes
+    return device_name_bytes
+
+# Functions to conver integer or float values to little endian fixed-point decimal
+def _pack_battery():
+    return pack('BB', BATTERY_UINT8, battery)
+
+def _pack_temperature(object_id):
+    if object_id == TEMPERATURE_SINT16:
+        temperature_bytes = pack('<Bh', TEMPERATURE_SINT16, round(temperature * _TEMPERATURE_SINT16_SCALING))
+    else:
+        temperature_bytes = bytes()
+    return temperature_bytes
+
+def _pack_humidity(object_id):
+    if object_id == HUMIDITY_UINT16:
+        humidity_bytes = pack('<Bh', HUMIDITY_UINT16, round(humidity * _HUMIDITY_UINT16_SCALING))
+    else:
+        humidity_bytes = bytes()
+    return humidity_bytes
+
+def _pack_pressure(object_id):
+    if object_id == PRESSURE_UINT24:
+        pressure_bytes = pack('<BL', PRESSURE_UINT24, round(pressure * _PRESSURE_UINT24_SCALING))[:-1]
+    else:
+        pressure_bytes = bytes()
+    return pressure_bytes
+
+def _pack_illuminance(object_id):
+    if object_id == ILLUMINANCE_UINT24:
+        illuminance_bytes = pack('<BL', ILLUMINANCE_UINT24, round(illuminance * _ILLUMINANCE_UINT24_SCALING))[:-1]
+    else:
+        illuminance_bytes = bytes()
+    return illuminance_bytes
+
+# Concatenate an arbitrary number of sensor readings using parameters of sensor data constants to indicate what's included.
+def _pack_service_data(*args):
+    service_data_bytes = pack('B', _SERVICE_DATA_UUID16)  # indicates a 16-bit service UUID follows
+    service_data_bytes += pack('<h', _SERVICE_UUID16)
+    service_data_bytes += pack('B', _DEVICE_INFO_FLAGS)
+    for object_id in args:
+        if object_id == BATTERY_UINT8:
+            service_data_bytes += _pack_battery()
+        if object_id == TEMPERATURE_SINT16:
+            service_data_bytes += _pack_temperature(TEMPERATURE_SINT16)
+        if object_id == HUMIDITY_UINT16:
+            service_data_bytes += _pack_humidity(HUMIDITY_UINT16)
+        if object_id == PRESSURE_UINT24:
+            service_data_bytes += _pack_pressure(PRESSURE_UINT24)
+        if object_id == ILLUMINANCE_UINT24:
+            service_data_bytes += _pack_illuminance(ILLUMINANCE_UINT24)
+    service_data_bytes = pack('B', len(service_data_bytes)) + service_data_bytes
+    return service_data_bytes
+
+# Construct advertising payload suitable for use by MicroPython's aioble.advertise(adv_data)
+def pack_advertisement(*args):
+    advertisement_bytes = _ADVERT_FLAGS  # All BTHome adverts start this way.
+    advertisement_bytes += _pack_device_name()
+    advertisement_bytes += _pack_service_data(*args)
+    assert len(advertisement_bytes) < _ADVERT_LENGTH_MAX
+    return advertisement_bytes