added SHT45 support

umnp/microcontroller/sensors/sht45/__init__.py

+try:
+    from machine import I2C
+except ImportError:
+    from umnp.microcontroller.umock.machine import I2C
+
+import asyncio
+import time
+
+SHT45_HIRES = 0xFD
+NO_HOLD_WAIT_TIME = 18.5 / 1000 / 1000
+SHT45_WAIT_TIME_MS = 9
+SHT45_RESET_TIME_MS = 1
+SHT45_SOFT_RESET = 0x94
+SHT45_DEFAULT_ADDRESS = 0x44
+
+
+class SHT45:
+    def __init__(self, i2c: I2C, i2c_address=SHT45_DEFAULT_ADDRESS):
+        self._i2c = i2c
+        self._i2c_address = i2c_address
+        self._initialised = False
+        self._nan = float("NAN")
+
+        devices = self._i2c.scan()
+
+        if self._i2c_address not in devices:
+            raise RuntimeError("SHT45: Device not found")
+
+        if self.reset():
+            self._initialised = True
+        else:
+            print("Could not initialise device")
+
+    @property
+    def initialised(self) -> bool:
+        return self._initialised
+
+    def _command(self, command: int) -> int:
+        pass
+
+    def _calulate_crc8(self, data, polynom=0x31, init=0xFF):
+        # CRC-8-Dallas/Maxim for I2C with 0x31 polynomial
+        crc = init
+        for byte in data:
+            crc ^= byte
+            for _ in range(8):
+                if crc & 0x80:
+                    crc = (crc << 1) ^ polynom
+                else:
+                    crc = crc << 1
+                crc &= 0xFF
+        return crc
+
+    def reset(self) -> bool:
+        cmd = bytearray(1)
+        cmd[0] = SHT45_SOFT_RESET
+        n_ack = self._i2c.writeto(self._i2c_address, cmd)
+        time.sleep(SHT45_RESET_TIME_MS / 1000)
+        if n_ack == 1:
+            return True
+        return False
+
+    def _decode_and_verify_value(self, buffer):
+        if self._calulate_crc8(buffer[:2]) != buffer[2]:
+            return self._nan
+
+        return buffer[1] + (buffer[0] << 8)
+
+    def _translate_temperature(self, buffer) -> float:
+        t_raw = self._decode_and_verify_value(buffer)
+        return -45 + 175 * t_raw / (2**16 - 1)
+
+    def _translate_rh(self, buffer):
+        rh_raw = self._decode_and_verify_value(buffer)
+        return -6 + 125 * rh_raw / (2**16 - 1)
+
+    async def measure(self):
+        temperature = self._nan
+        rh = self._nan
+        if not self.initialised:
+            return temperature, rh
+
+        cmd = bytearray(1)
+        cmd[0] = SHT45_HIRES
+        n_ack = self._i2c.writeto(self._i2c_address, cmd)
+        if n_ack != 1:
+            return temperature, rh
+        await asyncio.sleep(SHT45_WAIT_TIME_MS / 1000)
+
+        data = self._i2c.readfrom(self._i2c_address, 6)
+        temperature = self._translate_temperature(data[0:3])
+        rh = self._translate_rh(data[3:6])
+
+        return temperature, rh