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Adafruit_CircuitPython_OPT4048/adafruit_opt4048.py
foamyguy 20233d4c4b initial files
2025-05-22 16:37:56 -05:00

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# SPDX-FileCopyrightText: Copyright (c) 2025 Tim C for Adafruit Industries
#
# SPDX-License-Identifier: MIT
"""
`adafruit_opt4048`
================================================================================
CircuitPython driver library for the Adafruit OPT4048 breakout board, a high-speed,
high-precision tristimulus XYZ color sensor.
* Author(s): Tim C
Implementation Notes
--------------------
**Hardware:**
* `Adafruit OPT4048 Breakout <https://www.adafruit.com/products/6335>`_
**Software and Dependencies:**
* Adafruit CircuitPython firmware for the supported boards:
https://circuitpython.org/downloads
# * Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
# * Adafruit's Register library: https://github.com/adafruit/Adafruit_CircuitPython_Register
"""
# imports
__version__ = "0.0.0+auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_OPT4048.git"
from time import sleep
from adafruit_bus_device import i2c_device
from adafruit_register.i2c_bit import RWBit
from adafruit_register.i2c_bits import ROBits, RWBits
from adafruit_register.i2c_struct import UnaryStruct
from micropython import const
try:
from typing import ClassVar, Optional, Tuple
import busio
except ImportError:
pass
__version__ = "0.0.0+auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_OPT4048.git"
# Correct content of DEVICE_ID register
_OPT4048_CHIP_ID = const(0x0821) # OPT4048 default device id
class CV:
"""Constant value class helper for enums."""
# @classmethod
# def add_values(cls, value_tuples: Tuple[str, int, str, Optional[float]]) -> None:
# """Add CV values to the class"""
# cls.string = {}
# cls.lsb = {}
#
# for value_tuple in value_tuples:
# name, value, string, lsb = value_tuple
# setattr(cls, name, value)
# cls.string[value] = string
# cls.lsb[value] = lsb
@classmethod
def is_valid(cls, value: int) -> bool:
"""Validate that a given value is a member"""
IGNORE_LIST = [cls.__module__, cls.__name__]
print(IGNORE_LIST)
print(cls.__dict__.values())
if value in cls.__dict__.values() and value not in IGNORE_LIST:
return True
return False
class Range(CV):
"""Available range settings for the OPT4048 sensor.
Full-scale light level ranges as described in datasheet page 29.
+------------------------------+-------------------------+
| Setting | Range Value |
+==============================+=========================+
| :py:const:`Range.RANGE_2K` | 2.2 klux |
+------------------------------+-------------------------+
| :py:const:`Range.RANGE_4K` | 4.5 klux |
+------------------------------+-------------------------+
| :py:const:`Range.RANGE_9K` | 9 klux |
+------------------------------+-------------------------+
| :py:const:`Range.RANGE_18K` | 18 klux |
+------------------------------+-------------------------+
| :py:const:`Range.RANGE_36K` | 36 klux |
+------------------------------+-------------------------+
| :py:const:`Range.RANGE_72K` | 72 klux |
+------------------------------+-------------------------+
| :py:const:`Range.RANGE_144K` | 144 klux |
+------------------------------+-------------------------+
| :py:const:`Range.AUTO` | Auto-range |
+------------------------------+-------------------------+
"""
RANGE_2K = 0 # 2.2 klux
RANGE_4K = 1 # 4.5 klux
RANGE_9K = 2 # 9 klux
RANGE_18K = 3 # 18 klux
RANGE_36K = 4 # 36 klux
RANGE_72K = 5 # 72 klux
RANGE_144K = 6 # 144 klux
AUTO = 12 # Auto-range
class ConversionTime(CV):
"""Available conversion time settings for the OPT4048 sensor.
These control the device conversion time per channel as described in datasheet page 29.
+------------------------------------------+-------------------------+
| Setting | Time |
+==========================================+=========================+
| :py:const:`ConversionTime.TIME_600US` | 600 microseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_1MS` | 1 millisecond |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_1_8MS` | 1.8 milliseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_3_4MS` | 3.4 milliseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_6_5MS` | 6.5 milliseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_12_7MS` | 12.7 milliseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_25MS` | 25 milliseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_50MS` | 50 milliseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_100MS` | 100 milliseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_200MS` | 200 milliseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_400MS` | 400 milliseconds |
+------------------------------------------+-------------------------+
| :py:const:`ConversionTime.TIME_800MS` | 800 milliseconds |
+------------------------------------------+-------------------------+
"""
TIME_600US = 0 # 600 microseconds
TIME_1MS = 1 # 1 millisecond
TIME_1_8MS = 2 # 1.8 milliseconds
TIME_3_4MS = 3 # 3.4 milliseconds
TIME_6_5MS = 4 # 6.5 milliseconds
TIME_12_7MS = 5 # 12.7 milliseconds
TIME_25MS = 6 # 25 milliseconds
TIME_50MS = 7 # 50 milliseconds
TIME_100MS = 8 # 100 milliseconds
TIME_200MS = 9 # 200 milliseconds
TIME_400MS = 10 # 400 milliseconds
TIME_800MS = 11 # 800 milliseconds
class Mode(CV):
"""Available operating mode settings for the OPT4048 sensor.
Controls the device mode of operation as described in datasheet page 29.
+--------------------------------------+-------------------------+
| Setting | Mode |
+======================================+=========================+
| :py:const:`Mode.POWERDOWN` | Power-down mode |
+--------------------------------------+-------------------------+
| :py:const:`Mode.AUTO_ONESHOT` | Auto-range one-shot |
+--------------------------------------+-------------------------+
| :py:const:`Mode.ONESHOT` | One-shot mode |
+--------------------------------------+-------------------------+
| :py:const:`Mode.CONTINUOUS` | Continuous mode |
+--------------------------------------+-------------------------+
"""
POWERDOWN = 0 # Power-down mode
AUTO_ONESHOT = 1 # Forced auto-range one-shot mode
ONESHOT = 2 # One-shot mode
CONTINUOUS = 3 # Continuous mode
class FaultCount(CV):
"""Available fault count settings for the OPT4048 sensor.
Controls how many consecutive fault events are needed to trigger an interrupt.
+------------------------------------+-------------------------+
| Setting | Count |
+====================================+=========================+
| :py:const:`FaultCount.COUNT_1` | 1 fault count (default) |
+------------------------------------+-------------------------+
| :py:const:`FaultCount.COUNT_2` | 2 consecutive faults |
+------------------------------------+-------------------------+
| :py:const:`FaultCount.COUNT_4` | 4 consecutive faults |
+------------------------------------+-------------------------+
| :py:const:`FaultCount.COUNT_8` | 8 consecutive faults |
+------------------------------------+-------------------------+
"""
COUNT_1 = 0 # 1 fault count (default)
COUNT_2 = 1 # 2 consecutive fault counts
COUNT_4 = 2 # 4 consecutive fault counts
COUNT_8 = 3 # 8 consecutive fault counts
class IntConfig(CV):
"""Interrupt configuration settings for the OPT4048 sensor.
Controls the interrupt mechanism after end of conversion.
+----------------------------------------+----------------------------------+
| Setting | Configuration |
+========================================+==================================+
| :py:const:`IntConfig.SMBUS_ALERT` | SMBUS Alert |
+----------------------------------------+----------------------------------+
| :py:const:`IntConfig.DATA_READY_NEXT` | INT Pin data ready for next chan |
+----------------------------------------+----------------------------------+
| :py:const:`IntConfig.DATA_READY_ALL` | INT Pin data ready for all chans |
+----------------------------------------+----------------------------------+
"""
SMBUS_ALERT = 0 # SMBUS Alert
DATA_READY_NEXT = 1 # INT Pin data ready for next channel
DATA_READY_ALL = 3 # INT Pin data ready for all channels
# Default I2C address (ADDR pin connected to GND)
_OPT4048_DEFAULT_ADDR = const(0x44)
# Register addresses
_OPT4048_REG_CH0_MSB = const(0x00) # X channel MSB register
_OPT4048_REG_CH0_LSB = const(0x01) # X channel LSB register
_OPT4048_REG_CH1_MSB = const(0x02) # Y channel MSB register
_OPT4048_REG_CH1_LSB = const(0x03) # Y channel LSB register
_OPT4048_REG_CH2_MSB = const(0x04) # Z channel MSB register
_OPT4048_REG_CH2_LSB = const(0x05) # Z channel LSB register
_OPT4048_REG_CH3_MSB = const(0x06) # W channel MSB register
_OPT4048_REG_CH3_LSB = const(0x07) # W channel LSB register
_OPT4048_REG_THRESHOLD_LOW = const(0x08) # Low threshold register
_OPT4048_REG_THRESHOLD_HIGH = const(0x09) # High threshold register
_OPT4048_REG_CONFIG = const(0x0A) # Configuration register
_OPT4048_REG_THRESHOLD_CFG = const(0x0B) # Threshold configuration register
_OPT4048_REG_STATUS = const(0x0C) # Status register
_OPT4048_REG_DEVICE_ID = const(0x11) # Device ID register
# Status register (0x0C) bit flags
_OPT4048_FLAG_L = const(0x01) # Flag low - measurement smaller than threshold
_OPT4048_FLAG_H = const(0x02) # Flag high - measurement larger than threshold
_OPT4048_FLAG_CONVERSION_READY = const(0x04) # Conversion ready
_OPT4048_FLAG_OVERLOAD = const(0x08) # Overflow condition
class OPT4048:
"""Library for the OPT4048 Tristimulus XYZ Color Sensor
:param ~busio.I2C i2c_bus: The I2C bus the device is connected to
:param int address: The I2C device address. Defaults to :const:`0x44`
**Quickstart: Importing and using the device**
Here is an example of using the :class:`OPT4048`.
First you will need to import the libraries to use the sensor
.. code-block:: python
import board
from adafruit_opt4048 import OPT4048
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
sensor = OPT4048(i2c)
Now you have access to the color data
.. code-block:: python
x, y, z, w = sensor.color_data
"""
# _device_id = ROBits(16, _OPT4048_REG_DEVICE_ID, 0, register_width=2, lsb_first=False)
_device_id = UnaryStruct(_OPT4048_REG_DEVICE_ID, ">H")
_interrupt_direction = RWBit(_OPT4048_REG_THRESHOLD_CFG, 4, register_width=2, lsb_first=False)
_interrupt_config = RWBits(2, _OPT4048_REG_THRESHOLD_CFG, 2, register_width=2, lsb_first=False)
_interrupt_latch = RWBit(_OPT4048_REG_CONFIG, 3, register_width=2, lsb_first=False)
_interrupt_polarity = RWBit(_OPT4048_REG_CONFIG, 2, register_width=2, lsb_first=False)
_range = RWBits(4, _OPT4048_REG_CONFIG, 10, register_width=2, lsb_first=False)
_conversion_time = RWBits(4, _OPT4048_REG_CONFIG, 6, register_width=2, lsb_first=False)
_mode = RWBits(2, _OPT4048_REG_CONFIG, 4, register_width=2, lsb_first=False)
# Threshold Low register bits (register 0x08)
_threshold_low_exponent = RWBits(
4, _OPT4048_REG_THRESHOLD_LOW, 12, register_width=2, lsb_first=False
)
_threshold_low_mantissa = RWBits(
12, _OPT4048_REG_THRESHOLD_LOW, 0, register_width=2, lsb_first=False
)
_all_channels_raw = RWBits(
16 * 8, _OPT4048_REG_CH0_MSB, 0, register_width=2 * 8, lsb_first=False
)
def __init__(self, i2c_bus, address=_OPT4048_DEFAULT_ADDR):
self.i2c_device = i2c_device.I2CDevice(i2c_bus, address)
self.init()
def init(self):
"""Initialize the sensor and verify the device ID"""
# Check device ID
print(f"id: {hex(self._device_id)}")
if self._device_id != _OPT4048_CHIP_ID:
raise RuntimeError("Failed to find an OPT4048 sensor - check your wiring!")
# Initialize the sensor with default settings
self.interrupt_direction = True
self.interrupt_config = IntConfig.DATA_READY_ALL
self.interrupt_latch = True
self.interrupt_polarity = True # Use active-high interrupts by default
self.interrupt_config = IntConfig.DATA_READY_ALL
@property
def interrupt_direction(self):
"""Get the current interrupt direction setting.
Returns True if interrupts are generated when measurement > high threshold,
False if interrupts are generated when measurement < low threshold.
"""
return self._interrupt_direction
@interrupt_direction.setter
def interrupt_direction(self, value):
"""Set the direction of interrupt generation.
:param bool value: True for interrupt when measurement > high threshold,
False for interrupt when measurement < low threshold
"""
self._interrupt_direction = value
@property
def interrupt_config(self):
"""Get the current interrupt configuration.
Returns the current interrupt configuration mode.
See IntConfig class for valid values.
"""
return self._interrupt_config
@interrupt_config.setter
def interrupt_config(self, value):
"""Set the interrupt configuration.
:param int value: The interrupt configuration value.
Must be a valid IntConfig value.
"""
if not IntConfig.is_valid(value):
raise ValueError("Interrupt configuration must be a valid IntConfig value")
self._interrupt_config = value
@property
def interrupt_latch(self):
"""Get the current interrupt latch setting.
Returns True if interrupts are latched (interrupt flag remains active until
register is read), False if interrupts are transparent (interrupt flag
is updated with each measurement).
"""
return self._interrupt_latch
@interrupt_latch.setter
def interrupt_latch(self, value):
"""Set the interrupt latch mode.
:param bool value: True for latched interrupts (interrupt flag remains active
until register is read), False for transparent interrupts
(interrupt flag is updated with each measurement)
"""
self._interrupt_latch = value
@property
def interrupt_polarity(self):
"""Get the current interrupt pin polarity setting.
Returns True if interrupts are active-high (1 = interrupt active),
False if interrupts are active-low (0 = interrupt active).
"""
return self._interrupt_polarity
@interrupt_polarity.setter
def interrupt_polarity(self, value):
"""Set the interrupt pin polarity.
:param bool value: True for active-high interrupts (1 = interrupt active),
False for active-low interrupts (0 = interrupt active)
"""
self._interrupt_polarity = value
@property
def range(self):
"""Get the current range setting for light measurements.
Returns the current range setting from the Range enum.
This controls the full-scale light level range of the device.
See the Range class for valid values:
- Range.RANGE_2K: 2.2 klux
- Range.RANGE_4K: 4.5 klux
- Range.RANGE_9K: 9 klux
- Range.RANGE_18K: 18 klux
- Range.RANGE_36K: 36 klux
- Range.RANGE_72K: 72 klux
- Range.RANGE_144K: 144 klux
- Range.AUTO: Auto-range
"""
return self._range
@range.setter
def range(self, value):
"""Set the range for light measurements.
:param int value: The range setting to use from Range enum.
Controls the full-scale light level range.
Must be a valid Range value.
"""
if not Range.is_valid(value):
raise ValueError("Range setting must be a valid Range value")
self._range = value
@property
def conversion_time(self):
"""Get the current conversion time setting for the OPT4048 sensor.
Returns the current conversion time setting from the ConversionTime enum.
This controls the device conversion time per channel.
See the ConversionTime class for valid values:
- ConversionTime.TIME_600US: 600 microseconds
- ConversionTime.TIME_1MS: 1 millisecond
- ConversionTime.TIME_1_8MS: 1.8 milliseconds
- ConversionTime.TIME_3_4MS: 3.4 milliseconds
- ConversionTime.TIME_6_5MS: 6.5 milliseconds
- ConversionTime.TIME_12_7MS: 12.7 milliseconds
- ConversionTime.TIME_25MS: 25 milliseconds
- ConversionTime.TIME_50MS: 50 milliseconds
- ConversionTime.TIME_100MS: 100 milliseconds
- ConversionTime.TIME_200MS: 200 milliseconds
- ConversionTime.TIME_400MS: 400 milliseconds
- ConversionTime.TIME_800MS: 800 milliseconds
"""
return self._conversion_time
@conversion_time.setter
def conversion_time(self, value):
"""Set the conversion time for light measurements.
:param int value: The conversion time setting to use from ConversionTime enum.
Controls the device conversion time per channel.
Must be a valid ConversionTime value.
"""
if not ConversionTime.is_valid(value):
raise ValueError("Conversion time setting must be a valid ConversionTime value")
self._conversion_time = value
@property
def mode(self):
"""Get the current operating mode setting for the OPT4048 sensor.
Returns the current operating mode setting from the Mode enum.
This controls the device operating mode.
See the Mode class for valid values:
- Mode.POWERDOWN: Power-down mode
- Mode.AUTO_ONESHOT: Auto-range one-shot mode
- Mode.ONESHOT: One-shot mode
- Mode.CONTINUOUS: Continuous mode
"""
return self._mode
@mode.setter
def mode(self, value):
"""Set the operating mode of the sensor.
:param int value: The operating mode setting to use from Mode enum.
Controls the device's operating mode.
Must be a valid Mode value.
"""
if not Mode.is_valid(value):
raise ValueError("Mode setting must be a valid Mode value")
self._mode = value
def get_channels_raw(self):
"""Read all four channels, verify CRC, and return raw ADC code values.
Reads registers for channels 0-3 in one burst, checks the CRC bits for each,
and computes the raw ADC code values.
:return: Tuple of 4 raw channel values (X, Y, Z, W) if successful
:rtype: Tuple[int, int, int, int]
:raises RuntimeError: If CRC check fails for any channel
"""
# Read all channels in one operation using the ROBits accessor
all_channels_data = self._all_channels_raw
# Process each channel's data
channels = []
for ch in range(4):
# Extract channel data from the appropriate position in the buffer
# Each channel has 4 bytes (32 bits) of data
channel_offset = ch * 32
# Extract exponent (4 bits), MSB (12 bits), LSB (8 bits), and counter/CRC (8 bits)
exp = (all_channels_data >> (channel_offset + 28)) & 0xF
msb = (all_channels_data >> (channel_offset + 16)) & 0xFFF
lsb = (all_channels_data >> (channel_offset + 8)) & 0xFF
counter = (all_channels_data >> (channel_offset + 4)) & 0xF
crc = all_channels_data >> channel_offset & 0xF
# Combine MSB and LSB to form the 20-bit mantissa
mant = (msb << 8) | lsb
# print(f"ch: {ch} exp: {exp} msb: {msb} lsb: {lsb} counter: {counter} crc: {crc} mant: {mant}") # noqa: E501
# Calculate CRC
# Initialize CRC variables
x0 = 0 # CRC bit 0
x1 = 0 # CRC bit 1
x2 = 0 # CRC bit 2
x3 = 0 # CRC bit 3
# Calculate bit 0 (x0): XOR of all bits
# XOR all exponent bits
for i in range(4):
x0 ^= (exp >> i) & 1
# XOR all mantissa bits
for i in range(20):
x0 ^= (mant >> i) & 1
# XOR all counter bits
for i in range(4):
x0 ^= (counter >> i) & 1
# Calculate bit 1 (x1)
# Include counter bits 1 and 3
x1 ^= (counter >> 1) & 1 # COUNTER_CHx[1]
x1 ^= (counter >> 3) & 1 # COUNTER_CHx[3]
# Include odd-indexed mantissa bits
for i in range(1, 20, 2):
x1 ^= (mant >> i) & 1
# Include exponent bits 1 and 3
x1 ^= (exp >> 1) & 1 # E[1]
x1 ^= (exp >> 3) & 1 # E[3]
# Calculate bit 2 (x2)
# Include counter bit 3
x2 ^= (counter >> 3) & 1 # COUNTER_CHx[3]
# Include mantissa bits at positions 3,7,11,15,19
for i in range(3, 20, 4):
x2 ^= (mant >> i) & 1
# Include exponent bit 3
x2 ^= (exp >> 3) & 1 # E[3]
# Calculate bit 3 (x3)
# XOR mantissa bits at positions 3, 11, 19
x3 ^= (mant >> 3) & 1 # R[3]
x3 ^= (mant >> 11) & 1 # R[11]
x3 ^= (mant >> 19) & 1 # R[19]
# Combine bits to form the CRC
calculated_crc = (x3 << 3) | (x2 << 2) | (x1 << 1) | x0
# Verify CRC
if crc != calculated_crc:
raise RuntimeError(f"CRC check failed for channel {ch}")
# Convert to raw ADC value format (mantissa << exponent)
output = mant << exp
# Add to channels list
# channels.append(output)
channels.insert(0, output)
# Return all four channels (X, Y, Z, W)
return tuple(channels)
@property
def threshold_low(self):
"""Get the current low threshold value.
Returns the current low threshold value as a 32-bit integer.
This value determines when a low threshold interrupt is generated
when interrupt_direction is False.
"""
# Read the exponent and mantissa from the threshold low register
exponent = self._threshold_low_exponent
mantissa = self._threshold_low_mantissa
print(f"exponent: {exponent} mantissa: {mantissa}")
# Calculate ADC code value by applying the exponent as a bit shift
# ADD 8 to the exponent as per datasheet equations 12-13
return mantissa << (8 + exponent)
@threshold_low.setter
def threshold_low(self, value):
"""Set the low threshold value for interrupt generation.
:param int value: The low threshold value as a 32-bit integer
"""
# Find the appropriate exponent and mantissa values that represent the threshold
exponent = 0
mantissa = value
# The mantissa needs to fit in 12 bits, so we start by shifting right
# to determine how many shifts we need (which gives us the exponent)
# Note that the threshold registers already have 8 added to exponent
# internally so we first subtract 8 from our target exponent
if mantissa > 0xFFF: # If value won't fit in 12 bits
while mantissa > 0xFFF and exponent < 15:
mantissa >>= 1
exponent += 1
if mantissa > 0xFFF: # If still won't fit with max exponent, clamp
mantissa = 0xFFF
exponent = 15 - 8 # Max exponent (15) minus the 8 that's added internally
# Write the exponent and mantissa to the register
self._threshold_low_exponent = exponent
self._threshold_low_mantissa = mantissa
def get_cie(self):
"""Calculate CIE chromaticity coordinates and lux from raw sensor values.
Reads all four channels and calculates CIE x and y chromaticity coordinates
and illuminance (lux) using a matrix transformation.
:return: Tuple of CIE x, CIE y, and lux values
:rtype: Tuple[float, float, float]
"""
# Read all four channels using get_channels_raw
ch0, ch1, ch2, ch3 = self.get_channels_raw()
# Matrix multiplication coefficients (from datasheet)
m0x = 2.34892992e-04
m0y = -1.89652390e-05
m0z = 1.20811684e-05
m0l = 0
m1x = 4.07467441e-05
m1y = 1.98958202e-04
m1z = -1.58848115e-05
m1l = 2.15e-3
m2x = 9.28619404e-05
m2y = -1.69739553e-05
m2z = 6.74021520e-04
m2l = 0
m3x = 0
m3y = 0
m3z = 0
m3l = 0
# Matrix multiplication to calculate X, Y, Z, L values
# [ch0 ch1 ch2 ch3] * [m0x m0y m0z m0l] = [X Y Z Lux]
# [m1x m1y m1z m1l]
# [m2x m2y m2z m2l]
# [m3x m3y m3z m3l]
x = ch0 * m0x + ch1 * m1x + ch2 * m2x + ch3 * m3x
y = ch0 * m0y + ch1 * m1y + ch2 * m2y + ch3 * m3y
z = ch0 * m0z + ch1 * m1z + ch2 * m2z + ch3 * m3z
lux = ch0 * m0l + ch1 * m1l + ch2 * m2l + ch3 * m3l
# Calculate CIE x, y chromaticity coordinates
sum_xyz = x + y + z
if sum_xyz <= 0:
# Avoid division by zero
return 0.0, 0.0, 0.0
cie_x = x / sum_xyz
cie_y = y / sum_xyz
return cie_x, cie_y, lux
def calculate_color_temperature(self, cie_x, cie_y):
"""Calculate the correlated color temperature (CCT) in Kelvin.
Uses McCamy's approximation formula to calculate CCT from CIE 1931 x,y
coordinates. This is accurate for color temperatures between 2000K and
30000K.
Formula:
n = (x - 0.3320) / (0.1858 - y)
CCT = 437 * n^3 + 3601 * n^2 + 6861 * n + 5517
:param float cie_x: CIE x chromaticity coordinate
:param float cie_y: CIE y chromaticity coordinate
:return: The calculated color temperature in Kelvin
:rtype: float
"""
# Check for invalid coordinates
if cie_x == 0 and cie_y == 0:
return 0.0
# Calculate using McCamy's formula
# n = (x - 0.3320) / (0.1858 - y)
n = (cie_x - 0.3320) / (0.1858 - cie_y)
# CCT = 437 * n^3 + 3601 * n^2 + 6861 * n + 5517
cct = (437.0 * n * n * n) + (3601.0 * n * n) + (6861.0 * n) + 5517.0
return cct
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