I’ve just tried taking a pH reading & skipping the 3 point temperature calibration altogether, & using the same register value as used by the PC program (0x2000).
Raw pH readings.txt
phEcho 4. Get pH readings: SetAFE(2000) 400, 7879, 69, 7870, 7886, 277, 294, 312, 8040, 319, 8028, 327, 326, 134, 11, 293, 266, 7947, 327, 7927, 8191, 126, 7859, 326, 15, 307, 7886, 130, 312, 7877, 317, 7968, 8005, 109, 8122, 7863, 3, 8119, 177, 8107, 168, 7860, 297, 217, Info : halted: PC: 0x08007ab0 250, Info : halted: PC: 0x08007ab0 7854, Info : halted: PC: 0x08007ab0 7961, Info : halted: PC: 0x08007ab0 322, Info : halted: PC: 0x08007ab0 308, Info : halted: PC: 0x08007ab0 80, Info : halted: PC: 0x08007ab0 300, Info : halted: PC: 0x08007ab0 8023, 132, 8000, 7879, 101, 7867, 7881, 108, 7937, 322, 283, 7865, 8158, 71, 7963, 250, 328, 7905, 7873, 230, 7935, 8089, 8190, 8019, 74, 8187, 305, 270, 134, 322, 7952, 86, 199, 7947, 174, 107, 274, 278, 7919, 318, 7871, 7862, 7912, 257, 165, 7991, 7870, 7874, 7885, 7899, 276, 274, 7961, 8177, 326, 7963, 317, 8127, 299, 66, 36, 7871, 298, 322, 7921, 273, 7879, 332, 26, 312, 8102, 122, 326, 88, 301, 272, 7868, 7899, 301, 312, 289, 310, 321, 7884, 7945, 8141, 182, 7872, 7887, 7889, 251, 8132, 291, 8121, 7904, 7875, 13, 323, 315, 290, 65, 12, 7995, 8128, 7925, 7864, 28, 317, 79, 7955, 272, 7880, 8058, 301, 325, 280, 296, 8018, 7987, 310, 307, 7916, 8085, 7991, 8069, 7903, 7871, 7928, 309, 197, 7953, 306, 7881, 85, 246, 7867, 210, 264, 311, 7879, 188, 7900, 220, 326, 8006, 318, 54, 7978, 326, 129, 7916, 318, 193, 8006, 285, 97, 8054, 308, 7967, 8005, 122, 8047, 320, 7878, 7866, 128, 7925, 7927, 8159, 7874, 7914, 7867, 7877, 317, 7884, 7954, 316, 7930, 7863, 298, 306, 205, 7877, 83, 326, 7869, 7955, 8171, 7885, 304, 322, 8156, 287, 7975, 8074, 7890, 117, 162, 300, 7982, 186, 3, 313, 7960, 307, 257, 19, 304, 7909, 319, 7875, 7858, 7881, 7928, 8019, 7885, 7865, 7887, 85, 7869, 170, 7874, 153, 322, 8191, 8016, 326, 268, 7896, 225, 297, 219, 8020, 7977, 26, 332, 8111, 8087, 272, 7879, 7872, 8000, 285, 7952, 7892, 7878, 8033, 218, 7869, 8152, 7889, 7884, 145, 7861, 250, 168, 322, 323, 7958, 7863, 8028, 322, 305, 8156, 7941, 8010, 7892, 321, 272, 295, 8185, 322, 281, 285, 264, 263, 260, 46, 319, 314, 58, 8104, 304, 7897, 317, 311, 7959, 323, 181, 8057, 275, 242, 268, 163, 80, 312, 7864, 116, 238, 320, 197, 166, 283, 8063, 7961, 7907, 195, 7914, 8179, 7882, 300, 325, 8078, 7957, 7872, 8009, 8119, 7913, 76, 313, 318, 316, 7937, 325, 8040, 146, 8013, 152, 311, 7869, 8044, 8025, 203, 7934, 318, 296, 306, 72, 7887, 8139, 317, 327, 7954, 7865, 321, 312, 7872, 36, 192, 7978, 7943, 7974, 321, 8101, 7881, 7993, 104, 211, 8163, 8118, 144, 7911, 325, 8068, 214, 124, 289, 8133, 281, 8017, 82, 75, 8132, 280, 8, 7898, 8167, 7994, 7906, 245, 8109, 176, 8110, 315, 321, 7892, 8053, 99, 7895, 7890, 48, 7870, 7868, 8148, 306, 39, 313, 155, 317, 288, 7881, 8081, 7980, 276, 8182, 7891, 223, 8128, 7874, 315, 320, 245, 91, 311, 240, 281, 89, 8041, 92, 7974, 319, 7955, 7866, 325, 8067, 7908, 44, 286, 304, 8159, 318, 7864, 165, 7986, 7896, 8167, 322, 165, 278, 64, 164, 8004, 313, 296, 78, 118, 316, 59, 234, 8156, 7872, 310, 7897, 7889, 313, 318, 266, 7869, 93, 322, 296, 59, 7875, 7878, 293, 286, 300, 164, 321, 37, 7866, 318, 7885, 7988, 322, 325, 150, 7871, 7864, 311, 169, 186, 312, 322, 329, 324, 39, 7908, 7962, 71, 8094, 7866, 8024, 7968, 210, 7893, 8019, 8181, 24, 323, 60, 320, 8030, 11, 7876, 7878, 299, 7912, 7908, 7862, 294, 7870, 8090, 7880, 246, 324, 302, 265, 212, 7868, 8045, 307, 7881, 143, 7894, 318, 315, 7877, 7902, 304, 8083, 265, 7866, 314, 7870, 302, 269, 8177, 270, 189, 325, 225, 7949, 7871, 8169, 321, 7876, 280, 324, 323, 151, 7998, 314, 7907, 316, 281, 158, 7870, 325, 7873, 290, 189, 321, 317, 7948, 307, 7894, 8125, 8165, 322, 297, 137, 118, 67, 7920, 7890, 7940, 7891, 75, 7860, 320, 8067, 32, 8172, 7928, 312, 290, 321, 7917, 78, 7901, 316, 8139, 8181, 7962, 325, 7894, 289, 324, 7883, 7962, 7872, 326, 302, 180, 8000, 7999, 48, 7871, 319, 7869, 7886, 7908, 7900, 321, 302, 8012, 7870, 299, 319, 7880, 263, 320, 7897, 7999, 7872, 316, 330, 7875, 7894, 318, 7907, 323, 255, 256, 227, 300, 285, 247, 288, 7882, 7871, 102, 7898, 7906, 267, 7875, 327, 292, 7877, 330, 291, 325, 257, 8167, 268, 7888, 306, 203, 277, 7892, 171, 7908, 281, 171, 166, 7900, 8101, 33, 7987, 7866, 7863, 165, 7874, 7883, 232, 8016, 272, 312, 7868, 7882, 123, 145, 7866, 8019, 289, 322, 315, 92, 8129, 8171, 8172, 280, 193, 327, 216, 95, 275, 7874, 7873, 97, 8121, 8033, 318, 7932, 8053, 7870, 188, 8127, 7945, 7881, 8041, 316, 8034, 8179, 102, 7884, 117, 7939, 7916, 7876, 234, 7907, 7885, 310, 7864, 190, 62, 8030, 111, 7874, 7879, 7924, 237, 8024, 8037, 162, 7994, 291, 330, 126, 8155, 8066, 7863, 230, 7928, 7891, 8105, 132, 8116, 7960, 7896, 7909, 36, 245, 296, 8044, 7908, 7961, 266, 324, 7863, 7881, 11, 7878, 7869, 303, 7895, 8083, 146, 7905, 306, 309, 45, 328, 304, 7873, 7873, 8041, 7902, 7869, 7947, 7969, 254, 7967, 149, 7946, 220, 226, 8066, 152, 7888, 8056, 7867, 7912, 308, 324, 8030, 124, 8031, 115, 7872, 7889, 7974, 166, 7921, 188, 320, 7979, 293, 7921, 208, 301, 7862, 89, 7973, 105, 7882, 37, 44, 306, 7874, 8009, 271, 8171, 326, 7871, 318, 329, 7867, 322, 286, 313, 262, 75, 7868, 311, 7983, 287, 7923, 7859, 7940, 193, 238, 8012, 147, 313, 190, 7914, 7870, 7873, 278, 7877, 7902, 7879, 299, 7867, 136, 312, 176, 7870, 294, 130, 317, 7986, 302, 53, 8185, 325, 319, 8042, 288, 35, 291, 121, 69, 204, 207, 7869, 295, 7873, 323, 8123, 292, 316, 7879, 223, 276, 7934, 319, 7941, 236, 7988, 326, 8062, 231, 316, 51, 300, 8133, 7878, 7873, 323, 8158, 7865, 7882, 194, 304, 7, 8168, 180, 7945, 92, 286, 236, 8162, 7915, 149, 318, 7959, 8134, 7889, 7997, 7916, 7867, 37, 106, 7879, 295, 7918, 299, 228, 8010, 7864, 7906, 316, 7871, 295, 320, 214, 320, 7990, 7961, 233, 7879, 7959, 321, 7889, 182, 291, 7868, 7863, 8032, 325, 7879, 81, 317, 266, 8159, 200, 318, 8087, 224, 319, 7929, 7893, 7860, 7935, 7874, 323, 7999, 324, 322, 218, 317, 56, 311, 8185, 7870, 240, 7970, 23, 7927, 8095, 275, 319, 7903, 322, 250, 7960, 318, 328, 7889, 212, 7924, 307, 322, 310, 107, 7880, 7874, 274, 8177, 319, 7880, 7865, 277, 268, 291, 196, 322, 327, 309, 8113, 301, 310, 204, 137, 7873, 7861, 7935, 7915, 160, 194, 237, 8071, 7872, 7915, 149, 39, 240, 8080, 8125, 8024, 328, 8165, 7870, 7908, 178, 8091, 282, 7973, 7900, 287, 279, 8002, 7, 26, 83, 7952, 7916, 7953, 303, 185, 7988, 282, 7866, 115, 7867, 199, 7937, 7944, 7948, 321, 7871, 8189, 7940, 7872, 8091, 24, 7909, 8158, 8090, 8114, 7907, 282, 8173, 7872, 286, 229, 318, 221, 248, 7887, 141, 68, 316, 258, 7867, 293, 249, 277, 303, 268, 125, 121, 320, 8028, 180, 7901, 7888, 301, 7934, 7980, 199, 327, 290, 8038, 308, 105, 246, 222, 288, 313, 284, 8020, 177, 314, 224, 321, 310, 321, 299, 8056, 281, 316, 309, 281, 38, 228, 61, 8052, 274, 294, 24, 7933, 324, 301, 11, 200, 8165, 7895, 9, 7901, 98, 302, 23, 7864, 7869, 282, 7869, 7982, 127, 318, 7870, 7921, 7900, 7876, 8167, 8175, 7982, 326, 7988, 8044, 72, 8013, 201, 7946, 319, 318, 8079, 226, 262, 173, 297, 312, 7921, 329, 327, 8136, 132, 208, 7926, 8005, 316, 307, 318, 280, 7948, 292, 7964, 8181, 7879, 7966, 7875, 316, 8084, 7915, 8023, 283, 39, 168, 97, 7873, 167, 8009, 323, 7992, 8142, 324, 260, 7989, 7944, 137, 7975, 313, 8053, 7965, 8022, 300, 110, 301, 8113, 300, 319, 7871, 155, 7990, 7867, 7869, 129, 324, 7879, 238, 326, 329, 7890, 7890, 297, 7869, 8124, 280, 8184, 7896, 7941, 7866, 324, 8005, 7883, 236, 245, 8125, 305, 7915, 7987, 8184, 281, 7920, 7892, 238, 7993, 7890, 202, 164, 243, 164, 285, 7866, 94, 7892, 226, 7874, 292, 8088, 7866, 7870, 197, 8126, 57, 323, 196, 8023, 7917, 323, 7930, 8063, 32, 32, 7868, 54, 258, 7870, 324, 7957, 7876, 123, 172, 7941, 8126, 220, 8142, 8029, 7871, 318, 316, 8176, 248, 8110, 7891, 318, 316, 139, 8080, 38, 282, 188, 273, 184, 307, 7871, 7987, 326, 7869, 281, 8019, 70, 7874, 303, 55, 324, 7869, 8184, 317, 7969, 7870, 321, 7871, 309, 134, 7942, 322, 317, 7951, 8091, 296, 8187, 310, 8072, 7867, 221, 291, 7872, 8140, 204, 308, 7971, 315, 7935, 7902, 7894, 289, 321, 8147, 8098, 317, 8054, 22, 8034, 7966, 323, 280, 322, 213, 304, 321, 297, 208, 8017, 330, 7967, 7872, 7912, 7878, 7872, 7922, 297, 14, 212, 318, 318, 8118, 7980, 167, 186, 66, 7928, 7916, 297, 7924, 8094, 7915, 8106, 277, 7888, 59, 7869, 46, 8095, 234, 97, 8158, 7880, 7909, 63, 7885, 48, 53, 8150, 8189, 8065, 115, 312, 7952, 7865, 8100, 8038, 7942, 8101, 7859, 250, 281, 7914, 7991, 319, 289, 7918, 320, 282, 7935, 7875, 96, 331, 8123, 66, 326, 7885, 91, 7933, 18, 7866, 8094, 279, 7965, 318, 8066, 321, 7934, 8134, 282, 7861, 294, 8062, 319, 7878, 8112, 7869, 310, 59, 8111, 259, 315, 8116, 326, 7888, 269, 7877, 318, 7899, 0, 301, 8102, 25, 7973, 261, 7873, 7892, 14, 8108, 8091, 7993, 320, 8072, 7951, 320, 7990, 285, 8091, 7885, 8161, 7910, 7999, 249, 7955, 313, 328, 324, 7901, 7892, 134, 8075, 7920, 8165, 322, 166, 323, 179, 285, 317, 189, 7865, 7933, 8171, 326, 140, 8056, 134, 7874, 7985, 134, 322, 293, 303, 8096, 7874, 7932, 46, 295, 7870, 323, 325, 319, 153, 221, 7901, 136, 8, 307, 203, 215, 7864, 132, 8088, 7877, 284, 8141, 260, 7876, 7871, 7884, 177, 8026, 7988, 7870, 8063, 307, 313, 211, 8015, 320, 7911, 310, 8109, 8113, 306, 7900, 7945, 320, 7869, 311, 297, 283, 302, 307, 306, 7866, 321, 7876, 14, 322, 7871, 293, 7890, 222, 8183, 7874, 284, 8102, 174, 7894, 8127, 239, 121, 7940, 8016, 7975, 317, 292, 7966, 7874, 322, 280, 7984, 321, 106, 323, 7985, 106, 99, 86, 307, 244, 8178, 8125, 7888, 327, 7937, 204, 306, 70, 8029, 8096, 74, 7892, 311, 133, 8008, 7869, 7892, 321, 8108, 260, 7897, 329, 21, 7874, 8024, 8122, 8106, 8086, 110, 145, 8054, 263, 7868, 64, 7875, 163, 310, 292, 7947, 201, 7935, 7886, 289, 7912, 196, 7937, 294, 160, 316, 7864, 328, 116, 7917, 229, 293, 207, 7888, 320, 7878, 8061, 7963, 20, 8144, 328, 8084, 8137, 264, 189, 8042, 7934, 154, 319, 7871, 7877, 7887, 225, 326, 8057, 296, 8016, 187, 7959, 281, 214, 7996, 7912, 7870, 302, 144, 320, 7875, 324, 336, 7869, 7906, 155, 185, 7870, 8122, 299, 8083, 318, 8018, 135, 7871, 137, 7908, 188, 7871, 8086, 276, 8167, 7995, 315, 8144, 284, 8029, 204, 7870, 7998, 185, 7928, 8090, 209, 317, 7902, 298, 7868, 7909, 277, 8045, 7961, 327, 7888, 7871, 107, 8125, 8003, 280, 75, 7998, 292, 306, 270, 43, 111, 7979, 7938, 266, 298, 309, 8062, 219, 7878, 216, 271, 316, 47, 232, 269, 7931, 8012, 7875, 7872, 46, 7943, 7863, 7884, 7915, 289, 201, 306, 7876, 7874, 307, 317, 316, 7901, 7954, 8156, 243, 8168, 7880, 320, 277, 22, 318, 290, 132, 218, 8129, 7870, 308, 314, 281, 8033, 8114, 7881, 8046, 7925, 7893, 8000, 8004, 257, 8122, 8047, 7906, 7953, 14, 7866, 7988, 309, 8146, 4, 304, 7915, 199, 325, 205, 200, 7868, 8110, 7903, 286, 8069, 301, 7961, 8109, 122, 305, 7934, 8, 7890, 8159, 206, 7998, 7881, 89, 8089, 160, 7997, 63, 106, 8007, 7871, 262, 7928, 7969, 220, 7869, 8051, 7869, 7903, 7926, 327, 7921, 7954, 294, 325, 241, 7977, 8011, 270, 321, 8058, 286, 313, 8155, 7986, 63, 324, 238, 164, 325, 7877, 7867, 7876, 252, 7907, 7940, 148, 7882, 8107, 38, 8030, 180, 219, 228, 7871, 154, 7863, 7997, 7873, 7918, 8190, 187, 7887, 7937, 328, 7874, 7952, 7981, 284, 7866, 8180, 8056, 296, 7867, 8023, 8007, 7878, 254, 50, 8080, 7975, 8004, 300, 7885, 68, 163, 318, 8136, 272, 321, 7878, 7879, 118, 8149, 7913, 7948, 7933, 241, 7869, 206, 8021, 259, 7922, 65, 7866, 8154, 282, 323, 138, 7944, 327, 295, 317, 86, 316, 262, 240, 7869, 99, 258, 7937, 316, 114, 8015, 315, 311, 299, 7985, 8067, 150, 8135, 3, 323, 267, 7905, 7902, 291, 312, 192, 7872, 317, 217, Done! The 4 averages are: 1 3 40020000 f5a
I get the attached text file. The scatter of sample values is 50% of the ADC range. Why is it so noisy? When I bypass the AFE & using DC PSU, the readings are very stable (to within 2 or 3 LSB’s).
I note that the PC program has almost 1200 readings in the median column, & it must take ~ 5*1200 readings, adding up all of the columns: 6000 readings in a second, given the 1 second timebase in the other view of the same data. That’s 166 uSecs/sample. I’ve allowed a 160uSec delay between samples, so its about right.