138 lines
4.6 KiB
Python
138 lines
4.6 KiB
Python
# The MIT License (MIT)
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#
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# Copyright (c) 2018 Limor Fried
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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# THE SOFTWARE.
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"""
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`adafruit_am2320`
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====================================================
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This is a CircuitPython driver for the AM2320 temperature and humidity sensor.
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* Author(s): Limor Fried
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Implementation Notes
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--------------------
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**Hardware:**
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* Adafruit `AM2320 Temperature & Humidity Sensor
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<https://www.adafruit.com/product/3721>`_ (Product ID: 3721)
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**Software and Dependencies:**
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* Adafruit CircuitPython firmware for the ESP8622 and M0-based boards:
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https://github.com/adafruit/circuitpython/releases
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* Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
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"""
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# imports
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try:
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import struct
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except ImportError:
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import ustruct as struct
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import time
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from adafruit_bus_device.i2c_device import I2CDevice
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from micropython import const
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__version__ = "0.0.0-auto.0"
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__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_am2320.git"
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AM2320_DEFAULT_ADDR = const(0x5C)
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AM2320_CMD_READREG = const(0x03)
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AM2320_REG_TEMP_H = const(0x02)
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AM2320_REG_HUM_H = const(0x00)
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def _crc16(data):
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crc = 0xFFFF
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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 & 0x0001:
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crc >>= 1
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crc ^= 0xA001
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else:
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crc >>= 1
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return crc
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class AM2320:
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"""A driver for the AM2320 temperature and humidity sensor.
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:param i2c_bus: The `busio.I2C` object to use. This is the only required parameter.
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:param int address: (optional) The I2C address of the device.
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"""
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def __init__(self, i2c_bus, address=AM2320_DEFAULT_ADDR):
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for _ in range(3):
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# retry since we have to wake up the devices
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try:
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self._i2c = I2CDevice(i2c_bus, address)
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return
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except ValueError:
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pass
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time.sleep(0.25)
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raise ValueError("AM2320 not found")
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def _read_register(self, register, length):
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with self._i2c as i2c:
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# wake up sensor
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try:
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i2c.write(bytes([0x00]))
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except OSError:
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pass
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time.sleep(0.01) # wait 10 ms
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# Send command to read register
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cmd = [AM2320_CMD_READREG, register & 0xFF, length]
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# print("cmd: %s" % [hex(i) for i in cmd])
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i2c.write(bytes(cmd))
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time.sleep(0.002) # wait 2 ms for reply
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result = bytearray(length + 4) # 2 bytes pre, 2 bytes crc
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i2c.readinto(result)
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# print("$%02X => %s" % (register, [hex(i) for i in result]))
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# Check preamble indicates correct readings
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if result[0] != 0x3 or result[1] != length:
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raise RuntimeError("I2C read failure")
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# Check CRC on all but last 2 bytes
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crc1 = struct.unpack("<H", bytes(result[-2:]))[0]
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crc2 = _crc16(result[0:-2])
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if crc1 != crc2:
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raise RuntimeError("CRC failure 0x%04X vs 0x%04X" % (crc1, crc2))
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return result[2:-2]
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@property
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def temperature(self):
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"""The measured temperature in celsius."""
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temperature = struct.unpack(">H", self._read_register(AM2320_REG_TEMP_H, 2))[0]
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if temperature >= 32768:
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temperature = 32768 - temperature
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return temperature / 10.0
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@property
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def relative_humidity(self):
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"""The measured relative humidity in percent."""
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humidity = struct.unpack(">H", self._read_register(AM2320_REG_HUM_H, 2))[0]
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return humidity / 10.0
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