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bme280.c
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#include "bme280.h"
#include <stdio.h>
#include <stdlib.h>
#include <wiringPiI2C.h>
#include <math.h>
static int read_calibration(int bme280, struct bme280_calibration *calibration) {
calibration->dig_T1 = wiringPiI2CReadReg16(bme280, 0x88);
calibration->dig_T2 = wiringPiI2CReadReg16(bme280, 0x8a);
calibration->dig_T3 = wiringPiI2CReadReg16(bme280, 0x8c);
calibration->dig_P1 = wiringPiI2CReadReg16(bme280, 0x8e);
calibration->dig_P2 = wiringPiI2CReadReg16(bme280, 0x90);
calibration->dig_P3 = wiringPiI2CReadReg16(bme280, 0x92);
calibration->dig_P4 = wiringPiI2CReadReg16(bme280, 0x94);
calibration->dig_P5 = wiringPiI2CReadReg16(bme280, 0x96);
calibration->dig_P6 = wiringPiI2CReadReg16(bme280, 0x98);
calibration->dig_P7 = wiringPiI2CReadReg16(bme280, 0x9a);
calibration->dig_P8 = wiringPiI2CReadReg16(bme280, 0x9c);
calibration->dig_P9 = wiringPiI2CReadReg16(bme280, 0x9e);
calibration->dig_H1 = wiringPiI2CReadReg8(bme280, 0xa1);
calibration->dig_H2 = wiringPiI2CReadReg16(bme280, 0xe1);
calibration->dig_H3 = wiringPiI2CReadReg8(bme280, 0xe3);
uint8_t reg_E5 = wiringPiI2CReadReg8(bme280, 0xe5);
calibration->dig_H4 = (wiringPiI2CReadReg8(bme280, 0xe4) << 4) | (reg_E5 & 0xF);
calibration->dig_H5 = (reg_E5 >> 4) | (wiringPiI2CReadReg8(bme280, 0xe6) << 4);
calibration->dig_H6 = wiringPiI2CReadReg8(bme280, 0xe7);
}
static int32_t t_fine;
static int32_t compensate_t(int32_t adc_t, struct bme280_calibration *calib) {
int32_t var1, var2, t;
var1 = ((((adc_t >> 3) - ((int32_t) calib->dig_T1 << 1))) * ((int32_t) calib->dig_T2)) >> 11;
var2 = (((((adc_t >> 4) - ((int32_t) calib->dig_T1)) * ((adc_t >> 4) - ((int32_t) calib->dig_T1))) >> 12) *
((int32_t) calib->dig_T3)) >> 14;
t_fine = var1 + var2;
t = (t_fine * 5 + 128) >> 8;
return t;
}
static uint32_t compensate_p(int32_t adc_p, struct bme280_calibration *calib) {
int64_t var1, var2, p;
var1 = ((int64_t) t_fine) - 128000;
var2 = var1 * var1 * (int64_t) calib->dig_P6;
var2 = var2 + ((var1 * (int64_t) calib->dig_P5) << 17);
var2 = var2 + (((int64_t) calib->dig_P4) << 35);
var1 = ((var1 * var1 * (int64_t) calib->dig_P3) >> 8) + ((var1 * (int64_t) calib->dig_P2) << 12);
var1 = (((((int64_t) 1) << 47) + var1)) * ((int64_t) calib->dig_P1) >> 33;
if (var1 == 0) {
// avoid exception caused by division by zero
return 0;
}
p = 1048576 - adc_p;
p = (((p << 31) - var2) * 3125) / var1;
var1 = (((int64_t) calib->dig_P9) * (p >> 13) * (p >> 13)) >> 25; var2 = (((int64_t) calib->dig_P8) * p) >> 19;
p = ((p + var1 + var2) >> 8) + (((int64_t) calib->dig_P7) << 4);
return p;
}
static uint32_t compensate_h(int32_t adc_h, struct bme280_calibration *calib) {
int32_t v_x1_u32r;
v_x1_u32r = (t_fine - ((int32_t) 76800));
v_x1_u32r = (((((adc_h << 14) - (((int32_t) calib->dig_H4) << 20) - (((int32_t) calib->dig_H5) * v_x1_u32r)) +
((int32_t) 16384)) >> 15) * (((((((v_x1_u32r * ((int32_t) calib->dig_H6)) >> 10) * (((v_x1_u32r *
((int32_t) calib->dig_H3)) >> 11) + ((int32_t) 32768))) >> 10) + ((int32_t) 2097152)) *
((int32_t) calib->dig_H2) + 8192) >> 14));
v_x1_u32r = (v_x1_u32r - (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7) * ((int32_t) calib->dig_H1)) >> 4));
v_x1_u32r = (v_x1_u32r < 0 ? 0 : v_x1_u32r);
v_x1_u32r = (v_x1_u32r > 419430400 ? 419430400 : v_x1_u32r);
return (v_x1_u32r >> 12);
}
int main(void) {
int bme280 = wiringPiI2CSetup(bme280_address);
if (bme280 == -1) {
perror("wiringPiI2CSetup");
exit(EXIT_FAILURE);
}
uint8_t bme280_id = wiringPiI2CReadReg8(bme280, 0xd0);
if (bme280_id != 0x60) {
fprintf(stderr, "Invalid sensor id!\n");
exit(EXIT_FAILURE);
}
struct bme280_calibration calibration;
read_calibration(bme280, &calibration);
// set oversampling values
uint8_t osrs_p = 1;
uint8_t osrs_t = 1;
uint8_t osrs_h = 1;
wiringPiI2CWriteReg8(bme280, 0xf2, wiringPiI2CReadReg8(bme280, 0xf2) | osrs_h );
wiringPiI2CWriteReg8(bme280, 0xf4, (osrs_p << 5) | (osrs_p << 2) | (wiringPiI2CReadReg8(bme280, 0xf4) & 0x3));
// set IIR filter
wiringPiI2CWriteReg8(bme280, 0xf5, (wiringPiI2CReadReg8(bme280, 0xf5) & 0xe1) | (0x0 << 1));
// start measurement (set mode to forced)
wiringPiI2CWriteReg8(bme280, 0xf4, (wiringPiI2CReadReg8(bme280, 0xf4) & 0xfc) | 0x1);
while (wiringPiI2CReadReg8(bme280, 0xf3) & 0x8 != 0) {
}
// read measurements
int32_t adc_t = wiringPiI2CReadReg8(bme280, 0xfa) << 12 | wiringPiI2CReadReg8(bme280, 0xfb) << 4 | wiringPiI2CReadReg8(bme280, 0xfc) & 0xf;
uint32_t adc_p = wiringPiI2CReadReg8(bme280, 0xf7) << 12 | wiringPiI2CReadReg8(bme280, 0xf8) << 4 | wiringPiI2CReadReg8(bme280, 0xf9) & 0xf;
uint32_t adc_h = wiringPiI2CReadReg8(bme280, 0xfd) << 8 | wiringPiI2CReadReg8(bme280, 0xfe);
int32_t temp = compensate_t(adc_t, &calibration);
uint32_t pres = compensate_p(adc_p, &calibration);
uint32_t hum = compensate_h(adc_h, &calibration);
double temp_d = (double) temp / 100;
double pres_d = (double) pres / 256 / 100;
double hum_d = (double) hum / 1024;
// normaldruck
int height = 309;
pres_d = pres_d / pow(1 - 0.0065 * height / ((temp_d + 0.0065 * height) + 273.15), 0.03416 / 0.0065);
printf("Temperature: %.2f °C\n", temp_d);
printf("Pressure: %.2f hPa\n", pres_d);
printf("Humidity: %.2f %\n", hum_d);
}