Add calibration data. Turns out: illuminance_lx ≈ adc_counts

Illuminance:

    Number of Measurements: 1793

    Parameter temt6000_adc ∈ [0, 410, 394, 382, 429, 418, 383, 337, 340, 345, 326, 319, 355, 360, 406, 391, 332, 325, 324, 363, 387, 426, 443, 400, 402, 403, 398, 380, 336, 311, 341, 365, 358, 353, 413, 451, 463, 395, 386, 342, 339, 356, 396, 405, 285, 264, 254, 268, 246, 241, 255, 274, 293, 303, 290, 270, 281, 322, 334, 304, 318, 288, 282, 277, 301, 308, 298, 307, 306, 299, 284, 292, 333, 305, 346, 323, 328, 287, 296, 194, 309, 77, 87, 291, 272, 252, 237, 263, 297, 289, 302, 294, 260, 267, 257, 253, 262, 280, 315, 317, 310, 321, 331, 295, 283, 313, 278, 348, 233, 183, 197, 232, 211, 200, 223, 222, 210, 202, 207, 192, 189, 171, 161, 146, 152, 149, 151, 160, 147, 142, 166, 186, 178, 148, 150, 167, 139, 140, 117, 113, 112, 107, 81, 82, 75, 73, 70, 80, 83, 28, 16, 20, 19, 13, 14, 18, 15, 3, 2, 4, 37, 36, 29, 30, 38, 35, 22, 17, 23, 21, 12, 11, 24, 9, 10, 40, 42, 44, 49, 43, 33, 25, 39, 1, 7, 6, 8, 5, 41, 31, 34, 32, 26, 53, 51, 46, 60, 45, 61, 57, 58, 67, 85, 93, 106, 120, 105, 110, 116, 125, 114, 121, 165, 184, 170, 175, 187, 198, 137, 129, 109, 122, 132, 144, 145, 176, 173, 180, 181, 155, 162, 158, 141, 143, 130, 191, 205, 227, 228, 258, 250, 196, 206, 209, 261, 279, 327, 357, 381, 441, 505, 543, 487, 456, 464, 466, 524, 513, 512, 495, 430, 389, 373, 407, 435, 476, 493, 467, 448, 510, 459, 449, 423, 420, 393, 392, 367, 362, 439, 378, 415, 450, 438, 474, 468, 483, 416, 421, 399, 411, 424, 462, 518, 482, 535, 560, 523, 521, 545, 520, 515, 522, 534, 566, 600, 603, 552, 547, 595, 628, 710, 761, 783, 795, 790, 815, 898, 989, 987, 972, 889, 767, 683, 605, 553, 554, 576, 591, 607, 615, 586, 575, 592, 633, 701, 712, 750, 788, 831, 842, 756, 655, 766, 901, 947, 963, 896, 728, 436, 375, 502, 568, 485, 432, 661, 649, 676, 753, 741, 782, 618, 804, 884, 640, 434, 660, 444, 617, 668, 727, 853, 565, 691, 755, 812, 944, 769, 992, 997, 868, 730, 855, 494, 475, 539, 740, 719, 687, 816, 784, 959, 793, 619, 694, 737, 679, 848, 672, 629, 861, 919, 995, 913, 956, 999, 984, 912, 794, 827, 882, 845, 933, 940, 839, 811, 461, 570, 577, 713, 585, 208, 221, 275, 900, 720, 555, 390, 470, 574, 583, 662, 677, 504, 408, 372, 481, 425, 404, 465, 366, 244, 259, 271, 370, 329, 300, 276, 247, 185, 188, 243, 643, 597, 182, 157, 164, 231, 349, 484, 611, 648, 702, 742, 725, 733, 564, 479, 343, 316, 371, 409, 320, 286, 239, 238, 431, 458, 428, 213, 199, 203, 220, 216, 201, 190, 168, 79, 78, 71, 127, 86]

    Observation max44009_lx ∈ [0.00, 1387.00]

--- param model ---

Illuminance max44009_lx    : 2.5987834244105543 + 1.0599978822731602 * parameter(temt6000_adc)

Model error (mae) after cross validation (kfold, 10):

                          training   kfold XV   kfold XV

        Key   Attribute        LUT      model     static

Illuminance max44009_lx      2.25      10.27     216.68   :-)