Source code for adafruit_mcp9808

# SPDX-FileCopyrightText: 2017 Scott Shawcroft for Adafruit Industries
# SPDX-FileCopyrightText: 2021 Jose David Montoya
# SPDX-License-Identifier: MIT

"""
`adafruit_mcp9808`
====================================================

CircuitPython library to support MCP9808 high accuracy temperature sensor.

* Author(s): Scott Shawcroft, Jose David M.

Implementation Notes
--------------------

**Hardware:**

* `Adafruit MCP9808 High Accuracy I2C Temperature Sensor Breakout
  <https://www.adafruit.com/products/1782>`_ (Product ID: 1782)

**Software and Dependencies:**

* Adafruit CircuitPython firmware for the supported boards:
  https://github.com/adafruit/circuitpython/releases

* Adafruit's Bus Device library:
  https://github.com/adafruit/Adafruit_CircuitPython_BusDevice

* Adafruit's Register library:
  https://github.com/adafruit/Adafruit_CircuitPython_Register


**Notes:**

#.  Datasheet: http://www.adafruit.com/datasheets/MCP9808.pdf

"""

from micropython import const
from adafruit_bus_device.i2c_device import I2CDevice
from adafruit_register.i2c_bits import RWBits
from adafruit_register.i2c_bit import ROBit

__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_MCP9808.git"


_MCP9808_DEFAULT_ADDRESS = const(0x18)
_MCP9808_DEVICE_ID = const(0x54)
_MCP9808_REG_CONFIGURATION = const(0x01)
_MCP9808_REG_UPPER_TEMP = const(0x02)
_MCP9808_REG_LOWER_TEMP = const(0x03)
_MCP9808_REG_CRITICAL_TEMP = const(0x04)
_MCP9808_REG__TEMP = const(0x05)
_MCP9808_REG_MANUFACTURER_ID = const(0x06)
_MCP9808_REG_DEVICE_ID = const(0x07)
_MCP9808_REG_RESOLUTION = const(0x08)

# Resolution settings

_MCP9808_RESOLUTION_HALF_C = const(0x0)
_MCP9808_RESOLUTION_QUARTER_C = const(0x1)
_MCP9808_RESOLUTION_EIGHTH_C = const(0x2)
_MCP9808_RESOLUTION_SIXTEENTH_C = const(0x3)


[docs]class MCP9808: """Interface to the MCP9808 temperature sensor. :param ~busio.I2C i2c_bus: The I2C bus the MCP9808 is connected to. :param int address: The I2C address of the device. Defaults to :const:`0x18` **MCP9808 Settings** You could set the MCP9808 with different temperature limits and compare them with the ambient temperature Ta - above_ct this value will be set to `True` when Ta is above this limit - above_ut: this value will be set to `True` when Ta is above this limit - below_lt: this value will be set to `True` when Ta is below this limit To get this value, you will need to read the temperature, and then access the attribute **Quickstart: Importing and using the MCP9808** Here is an example of using the :class:`MCP9808` class. First you will need to import the libraries to use the sensor .. code-block:: python import board import adafruit_mcp9808 Once this is done you can define your `board.I2C` object and define your sensor object .. code-block:: python i2c = board.I2C() # uses board.SCL and board.SDA mcp = adafruit_mcp9808.MCP9808(i2c_bus) Now you have access to the change in temperature using the :attr:`temperature` attribute. This temperature is in Celsius. .. code-block:: python temperature = mcp.temperature """ _MCP9808_REG_RESOLUTION_SET = RWBits(2, 0x08, 0, register_width=2) above_critical = ROBit(_MCP9808_REG__TEMP, 7, register_width=1) """True when the temperature is above the currently set critical temperature. False Otherwise""" above_upper = ROBit(_MCP9808_REG__TEMP, 6, register_width=1) """True when the temperature is above the currently set high temperature. False Otherwise""" below_lower = ROBit(_MCP9808_REG__TEMP, 5, register_width=1) """True when the temperature is below the currently set lower temperature. False Otherwise""" def __init__(self, i2c_bus, address=_MCP9808_DEFAULT_ADDRESS): self.i2c_device = I2CDevice(i2c_bus, address) # Verify the manufacturer and device ids to ensure we are talking to # what we expect. self.buf = bytearray(3) self.buf[0] = _MCP9808_REG_MANUFACTURER_ID with self.i2c_device as i2c: i2c.write_then_readinto(self.buf, self.buf, out_end=1, in_start=1) ok = self.buf[2] == _MCP9808_DEVICE_ID and self.buf[1] == 0 # Check device id. self.buf[0] = _MCP9808_REG_DEVICE_ID with self.i2c_device as i2c: i2c.write_then_readinto(self.buf, self.buf, out_end=1, in_start=1) if not ok or self.buf[1] != 0x04: raise ValueError( "Unable to find MCP9808 at i2c address " + str(hex(address)) ) @property def temperature(self): """Temperature in Celsius. Read-only.""" self.buf[0] = _MCP9808_REG__TEMP with self.i2c_device as i2c: i2c.write_then_readinto(self.buf, self.buf, out_end=1, in_start=1) return self._temp_conv() def _temp_conv(self): """Internal function to convert temperature given by the sensor""" # Clear flags from the value self.buf[1] = self.buf[1] & 0x1F if self.buf[1] & 0x10 == 0x10: self.buf[1] = self.buf[1] & 0x0F return (self.buf[1] * 16 + self.buf[2] / 16.0) - 256 return self.buf[1] * 16 + self.buf[2] / 16.0 def _limit_temperatures(self, temp, t_address=0x02): """Internal function to setup limit temperature :param int temp: temperature limit :param int t_address: register address for the temperature limit 0x02 : Upper Limit 0x03 : Lower Limit 0x04 : Critical Limit """ if temp < 0: negative = True temp = abs(temp) else: negative = False self.buf[0] = t_address self.buf[1] = temp >> 4 if negative: self.buf[1] = self.buf[1] | 0x10 self.buf[2] = (temp & 0x0F) << 4 with self.i2c_device as i2c: i2c.write(self.buf) def _get_temperature(self, address): self.buf[0] = address with self.i2c_device as i2c: i2c.write_then_readinto(self.buf, self.buf, out_end=1, in_start=1) return self._temp_conv() def _set_temperature(self, temp, address): self._limit_temperatures(temp, address) @property def upper_temperature(self): """Upper alarm temperature in Celsius""" return self._get_temperature(_MCP9808_REG_UPPER_TEMP) @upper_temperature.setter def upper_temperature(self, temp): """Setup Upper temperature""" self._limit_temperatures(temp, _MCP9808_REG_UPPER_TEMP) @property def lower_temperature(self): """Lower alarm temperature in Celsius""" return self._get_temperature(_MCP9808_REG_LOWER_TEMP) @lower_temperature.setter def lower_temperature(self, temp): """Setup Lower temperature""" self._limit_temperatures(temp, _MCP9808_REG_LOWER_TEMP) @property def critical_temperature(self): """Critical alarm temperature in Celsius""" return self._get_temperature(_MCP9808_REG_CRITICAL_TEMP) @critical_temperature.setter def critical_temperature(self, temp): """Setup Critical temperature""" self._limit_temperatures(temp, _MCP9808_REG_CRITICAL_TEMP) @property def resolution(self): """Temperature Resolution in Celsius ======= ============ ============== Value Resolution Reading Time ======= ============ ============== 0 0.5°C 30 ms 1 0.25°C 65 ms 2 0.125°C 130 ms 3 0.0625°C 250 ms ======= ============ ============== """ return self._MCP9808_REG_RESOLUTION_SET @resolution.setter def resolution(self, resol_value=3): """ Setup Critical temperature""" self._MCP9808_REG_RESOLUTION_SET = resol_value # pylint: disable=invalid-name