1 files changed, 52 insertions, 0 deletions
diff --git a/include/py/homekit/temphum/i2c.py b/include/py/homekit/temphum/i2c.py
new file mode 100644
index 0000000..7d8e2e3
--- /dev/null
+++ b/include/py/homekit/temphum/i2c.py
@@ -0,0 +1,52 @@
+import abc
+import smbus
+
+from .base import BaseSensor, SensorType
+
+
+class I2CSensor(BaseSensor, abc.ABC):
+    def __init__(self, bus: int):
+        super().__init__()
+        self.bus = smbus.SMBus(bus)
+
+
+class DHT12(I2CSensor):
+    i2c_addr = 0x5C
+
+    def _measure(self):
+        raw = self.bus.read_i2c_block_data(self.i2c_addr, 0, 5)
+        if (raw[0] + raw[1] + raw[2] + raw[3]) & 0xff != raw[4]:
+            raise ValueError("checksum error")
+        return raw
+
+    def temperature(self) -> float:
+        raw = self._measure()
+        temp = raw[2] + (raw[3] & 0x7f) * 0.1
+        if raw[3] & 0x80:
+            temp *= -1
+        return temp
+
+    def humidity(self) -> float:
+        raw = self._measure()
+        return raw[0] + raw[1] * 0.1
+
+
+class Si7021(I2CSensor):
+    i2c_addr = 0x40
+
+    def temperature(self) -> float:
+        raw = self.bus.read_i2c_block_data(self.i2c_addr, 0xE3, 2)
+        return 175.72 * (raw[0] << 8 | raw[1]) / 65536.0 - 46.85
+
+    def humidity(self) -> float:
+        raw = self.bus.read_i2c_block_data(self.i2c_addr, 0xE5, 2)
+        return 125.0 * (raw[0] << 8 | raw[1]) / 65536.0 - 6.0
+
+
+def create_sensor(type: SensorType, bus: int) -> BaseSensor:
+    if type == SensorType.Si7021:
+        return Si7021(bus)
+    elif type == SensorType.DHT12:
+        return DHT12(bus)
+    else:
+        raise ValueError('unexpected sensor type')