1  # The MIT License (MIT)
  2  #
  3  # Copyright (c) 2017 Scott Shawcroft for Adafruit Industries.
  4  #
  5  # Permission is hereby granted, free of charge, to any person obtaining a copy
  6  # of this software and associated documentation files (the "Software"), to deal
  7  # in the Software without restriction, including without limitation the rights
  8  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  9  # copies of the Software, and to permit persons to whom the Software is
 10  # furnished to do so, subject to the following conditions:
 11  #
 12  # The above copyright notice and this permission notice shall be included in
 13  # all copies or substantial portions of the Software.
 14  #
 15  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 16  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 17  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 18  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 19  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 20  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 21  # THE SOFTWARE.
 22  """
 23  `adafruit_mcp9808` - MCP9808 I2C Temperature Sensor
 24  ====================================================
 25  
 26  CircuitPython library to support MCP9808 high accuracy temperature sensor.
 27  
 28  * Author(s): Scott Shawcroft
 29  
 30  Implementation Notes
 31  --------------------
 32  
 33  **Hardware:**
 34  
 35  * Adafruit `MCP9808 High Accuracy I2C Temperature Sensor Breakout
 36    <https://www.adafruit.com/products/1782>`_ (Product ID: 1782)
 37  
 38  **Software and Dependencies:**
 39  
 40  * Adafruit CircuitPython firmware (0.8.0+) for the ESP8622 and M0-based boards:
 41    https://github.com/adafruit/circuitpython/releases
 42  * Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
 43  
 44  **Notes:**
 45  
 46  #.  Datasheet: http://www.adafruit.com/datasheets/MCP9808.pdf
 47  
 48  """
 49  
 50  __version__ = "0.0.0-auto.0"
 51  __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_MCP9808.git"
 52  
 53  from adafruit_bus_device.i2c_device import I2CDevice
 54  
 55  # Resolution settings
 56  HALF_C = 0x0
 57  QUARTER_C = 0x1
 58  EIGHTH_C = 0x2
 59  SIXTEENTH_C = 0x3
 60  
 61  
 62  class MCP9808:
 63      """Interface to the MCP9808 temperature sensor."""
 64  
 65      # alert_lower_temperature_bound
 66      # alert_upper_temperature_bound
 67      # critical_temperature
 68      # temperature
 69      # temperature_resolution
 70  
 71      def __init__(self, i2c_bus, address=0x18):
 72          self.i2c_device = I2CDevice(i2c_bus, address)
 73  
 74          # Verify the manufacturer and device ids to ensure we are talking to
 75          # what we expect.
 76          self.buf = bytearray(3)
 77          self.buf[0] = 0x06
 78          with self.i2c_device as i2c:
 79              i2c.write_then_readinto(self.buf, self.buf, out_end=1, in_start=1)
 80  
 81          ok = self.buf[2] == 0x54 and self.buf[1] == 0
 82  
 83          # Check device id.
 84          self.buf[0] = 0x07
 85          with self.i2c_device as i2c:
 86              i2c.write_then_readinto(self.buf, self.buf, out_end=1, in_start=1)
 87  
 88          if not ok or self.buf[1] != 0x04:
 89              raise ValueError(
 90                  "Unable to find MCP9808 at i2c address " + str(hex(address))
 91              )
 92  
 93      @property
 94      def temperature(self):
 95          """Temperature in celsius. Read-only."""
 96          self.buf[0] = 0x05
 97          with self.i2c_device as i2c:
 98              i2c.write_then_readinto(self.buf, self.buf, out_end=1, in_start=1)
 99  
100          # Clear flags from the value
101          self.buf[1] = self.buf[1] & 0x1F
102          if self.buf[1] & 0x10 == 0x10:
103              self.buf[1] = self.buf[1] & 0x0F
104              return (self.buf[1] * 16 + self.buf[2] / 16.0) - 256
105          return self.buf[1] * 16 + self.buf[2] / 16.0