Adolfo Reyna
102 lines
2.7 KiB
Python
102 lines
2.7 KiB
Python
"""CircuitPython SHTC3 temperature and humidity sensor driver.
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Uses standard I2C transactions with bus locking.
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"""
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import time
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class SHTC3:
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ADDR = 0x70
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WAKE = b'\x35\x17'
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SLEEP = b'\xB0\x98'
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MEASURE = b'\x78\x66' # High precision, T first, clock stretching disabled
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def __init__(self, i2c):
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self.i2c = i2c
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def _crc8(self, data):
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crc = 0xFF
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for byte in data:
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crc ^= byte
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for _ in range(8):
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if crc & 0x80:
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crc = (crc << 1) ^ 0x31
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else:
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crc <<= 1
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crc &= 0xFF
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return crc
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def read_sensor(self):
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try:
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# 1. Wakeup
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while not self.i2c.try_lock():
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pass
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try:
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self.i2c.writeto(self.ADDR, self.WAKE)
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finally:
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self.i2c.unlock()
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time.sleep(0.001)
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# 2. Trigger Measurement
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while not self.i2c.try_lock():
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pass
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try:
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self.i2c.writeto(self.ADDR, self.MEASURE)
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finally:
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self.i2c.unlock()
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time.sleep(0.015)
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# 3. Read 6 bytes of data
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# bytes 0, 1: Temp, byte 2: Temp CRC
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# bytes 3, 4: Hum, byte 5: Hum CRC
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buf = bytearray(6)
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while not self.i2c.try_lock():
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pass
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try:
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self.i2c.readfrom_into(self.ADDR, buf)
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finally:
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self.i2c.unlock()
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# 4. Enter sleep mode
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while not self.i2c.try_lock():
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pass
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try:
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self.i2c.writeto(self.ADDR, self.SLEEP)
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finally:
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self.i2c.unlock()
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# Verify CRC
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t_data = buf[0:2]
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t_crc = buf[2]
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h_data = buf[3:5]
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h_crc = buf[5]
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if self._crc8(t_data) != t_crc:
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print("SHTC3 Temp CRC error")
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return None, None
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if self._crc8(h_data) != h_crc:
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print("SHTC3 Hum CRC error")
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return None, None
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raw_t = (buf[0] << 8) | buf[1]
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raw_h = (buf[3] << 8) | buf[4]
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temp = -45.0 + 175.0 * (raw_t / 65536.0)
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hum = 100.0 * (raw_h / 65536.0)
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return round(temp, 2), round(hum, 2)
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except Exception as e:
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print(f"Error reading SHTC3 sensor: {e}")
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try:
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while not self.i2c.try_lock():
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pass
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try:
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self.i2c.writeto(self.ADDR, self.SLEEP)
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finally:
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self.i2c.unlock()
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except:
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pass
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return None, None
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