121 lines
5 KiB
C
121 lines
5 KiB
C
// Copyright 2026 A.M. Rowsell <amr@frzn.dev>
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// SPDX-License-Identifier: MIT
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#include "./bmp.h"
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static const uint8_t BMP_RESET[2] = {0x7E, 0xB6};
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static const uint8_t BMP_CAL_DATA[21];
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static const uint8_t BMP_SETUP[6] = {0x1C, 0x0B, 0x1D, 0x08, 0x1F, 0x0A};
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static const uint8_t BMP_START[2] = {0x1B, 0x33};
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float bmp_cal_data_fp[15];
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int getBMPData(i2c_inst_t *i2c, float *temperature, float *pressure) {
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uint8_t rawMeasurements[7];
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uint32_t rawTemp;
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uint32_t rawPress;
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i2c_write_blocking(i2c, BMP_ADDR, &BMP_STATUS, 1, true);
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i2c_read_blocking(i2c, BMP_ADDR, rawMeasurements, 7,
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false); // read status & 6 data bytes
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if ((rawMeasurements[0] & 0x60) != 0x60) {
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// no measurements ready
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return 1;
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}
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rawPress = (rawMeasurements[3] << 16) | (rawMeasurements[2] << 8) |
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rawMeasurements[1];
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rawTemp = (rawMeasurements[6] << 16) | (rawMeasurements[5] << 8) |
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rawMeasurements[4];
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// now for the crazy math
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float partial_data1;
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float partial_data2;
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float t_lin;
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partial_data1 = (float)(rawTemp - bmp_cal_data_fp[PAR_T1]);
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partial_data2 = (float)(partial_data1 * bmp_cal_data_fp[PAR_T2]);
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t_lin =
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partial_data2 + (partial_data1 * partial_data1) * bmp_cal_data_fp[PAR_T3];
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// t_lin is compensated temperature
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float comp_press;
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float partial_data3;
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float partial_data4;
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float partial_out1;
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float partial_out2;
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partial_data1 = bmp_cal_data_fp[PAR_P6] * t_lin;
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partial_data2 = bmp_cal_data_fp[PAR_P7] * (t_lin * t_lin);
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partial_data3 = bmp_cal_data_fp[PAR_P8] * (t_lin * t_lin * t_lin);
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partial_out1 =
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bmp_cal_data_fp[PAR_P5] + partial_data1 + partial_data2 + partial_data3;
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partial_data1 = bmp_cal_data_fp[PAR_P2] * t_lin;
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partial_data2 = bmp_cal_data_fp[PAR_P3] * (t_lin * t_lin);
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partial_data3 = bmp_cal_data_fp[PAR_P4] * (t_lin * t_lin * t_lin);
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partial_out2 = (float)rawPress * (bmp_cal_data_fp[PAR_P1] + partial_data1 +
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partial_data2 + partial_data3);
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partial_data1 = (float)rawPress * (float)rawPress;
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partial_data2 = bmp_cal_data_fp[PAR_P9] + bmp_cal_data_fp[PAR_P10] * t_lin;
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partial_data3 = partial_data1 * partial_data2;
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partial_data4 =
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partial_data3 + ((float)rawPress * (float)rawPress * (float)rawPress) *
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bmp_cal_data_fp[PAR_P11];
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comp_press = partial_out1 + partial_out2 + partial_data4;
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*temperature = t_lin;
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*pressure = comp_press;
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return 0;
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}
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int getBMPCalData(i2c_inst_t *i2c, bmp_cal_data_t *calData) {
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uint8_t rawValues[21];
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i2c_write_blocking(i2c, BMP_ADDR, &BMP_CAL_ADDR, 1, true);
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i2c_read_blocking(i2c, BMP_ADDR, rawValues, BMP_CAL_LEN, false);
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calData->NVM_PAR_T1 = (uint16_t)((rawValues[1] << 8) | rawValues[0]);
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calData->NVM_PAR_T2 = (uint16_t)((rawValues[3] << 8) | rawValues[2]);
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calData->NVM_PAR_T3 = (int8_t)(rawValues[4]);
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calData->NVM_PAR_P1 = (int16_t)((rawValues[6] << 8) | rawValues[5]);
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calData->NVM_PAR_P2 = (int16_t)((rawValues[8] << 8) | rawValues[7]);
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calData->NVM_PAR_P3 = (int8_t)(rawValues[9]);
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calData->NVM_PAR_P4 = (int8_t)(rawValues[10]);
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calData->NVM_PAR_P5 = (uint16_t)((rawValues[12] << 8) | rawValues[11]);
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calData->NVM_PAR_P6 = (uint16_t)((rawValues[14] << 8) | rawValues[13]);
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calData->NVM_PAR_P7 = (int8_t)(rawValues[15]);
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calData->NVM_PAR_P8 = (int8_t)(rawValues[16]);
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calData->NVM_PAR_P9 = (int16_t)((rawValues[18] << 8) | rawValues[17]);
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calData->NVM_PAR_P10 = (int8_t)(rawValues[19]);
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calData->NVM_PAR_P11 = (int8_t)(rawValues[20]);
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// convert cal values to floating point, adjusted values
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bmp_cal_data_fp[PAR_T1] = (float)calData->NVM_PAR_T1 / pow(2, -8);
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bmp_cal_data_fp[PAR_T2] = (float)calData->NVM_PAR_T2 / pow(2, 30);
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bmp_cal_data_fp[PAR_T3] = (float)calData->NVM_PAR_T3 / pow(2, 48);
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bmp_cal_data_fp[PAR_P1] =
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((float)calData->NVM_PAR_P1 - pow(2, 14)) / pow(2, 20);
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bmp_cal_data_fp[PAR_P2] =
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((float)calData->NVM_PAR_P2 - pow(2, 14)) / pow(2, 29);
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bmp_cal_data_fp[PAR_P3] = (float)calData->NVM_PAR_P3 / pow(2, 32);
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bmp_cal_data_fp[PAR_P4] = (float)calData->NVM_PAR_P4 / pow(2, 37);
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bmp_cal_data_fp[PAR_P5] = (float)calData->NVM_PAR_P5 / pow(2, -3);
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bmp_cal_data_fp[PAR_P6] = (float)calData->NVM_PAR_P6 / pow(2, 6);
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bmp_cal_data_fp[PAR_P7] = (float)calData->NVM_PAR_P7 / pow(2, 8);
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bmp_cal_data_fp[PAR_P8] = (float)calData->NVM_PAR_P8 / pow(2, 15);
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bmp_cal_data_fp[PAR_P9] = (float)calData->NVM_PAR_P9 / pow(2, 48);
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bmp_cal_data_fp[PAR_P10] = (float)calData->NVM_PAR_P10 / pow(2, 48);
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bmp_cal_data_fp[PAR_P11] = (float)calData->NVM_PAR_P11 / pow(2, 65);
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return 0;
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}
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int initBMP(i2c_inst_t *i2c) {
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bmp_cal_data_t bmpRawCalValues, *bmpRawCalValues_t = &bmpRawCalValues;
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i2c_write_blocking(i2c, BMP_ADDR, BMP_RESET, 2, false); // send reset
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sleep_ms(2); // wait for reset to complete
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getBMPCalData(i2c, bmpRawCalValues_t);
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i2c_write_blocking(i2c, BMP_ADDR, BMP_SETUP, 6,
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false); // set up sampling parameters
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i2c_write_blocking(i2c, BMP_ADDR, BMP_START, 2,
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false); // start automatic measurements
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return 0;
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}
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