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convert bme280 pressure number

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Travis Shears 2025-04-09 12:07:18 +02:00
parent 659e98dbc6
commit be5b5ca2d5
3 changed files with 47 additions and 13 deletions
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56
bme280.c
View file

@ -115,9 +115,9 @@ static void bmp280_get_compensation_params(i2c_inst_t *i2c,
params->dig_h5 = (int16_t)(buf[33] << 8) | buf[32]; params->dig_h5 = (int16_t)(buf[33] << 8) | buf[32];
} }
// Main Config for the sensor. Defined here so it can be use to inital configure the sensor and to proc further reads // Main Config for the sensor. Defined here so it can be use to inital configure
// 001 sets osrs_t temp over sampling to 1, 001 sets osrs_p pressure // the sensor and to proc further reads 001 sets osrs_t temp over sampling to 1,
// oversampling to 1, 01 sets sensor mode to forced // 001 sets osrs_p pressure oversampling to 1, 01 sets sensor mode to forced
static const uint8_t main_config = 0b00100101; static const uint8_t main_config = 0b00100101;
void bme280_init(bme280_config *config, i2c_inst_t *i2c, uint8_t sda_pin, void bme280_init(bme280_config *config, i2c_inst_t *i2c, uint8_t sda_pin,
uint8_t scl_pin) { uint8_t scl_pin) {
@ -179,7 +179,7 @@ static void bme280_read_raw(bme280_config *config, int32_t *temp,
*temp = (buf[3] << 12) | (buf[4] << 4) | (buf[5] >> 4); *temp = (buf[3] << 12) | (buf[4] << 4) | (buf[5] >> 4);
} }
float bmp280_convert_temp(bme280_config *config, int32_t temp) { static int32_t bme280_caculate_t_fine(bme280_config *config, int32_t temp) {
bme280_compensation_params params = config->params; bme280_compensation_params params = config->params;
int32_t var1, var2; int32_t var1, var2;
var1 = ((((temp >> 3) - ((int32_t)params.dig_t1 << 1))) * var1 = ((((temp >> 3) - ((int32_t)params.dig_t1 << 1))) *
@ -190,11 +190,44 @@ float bmp280_convert_temp(bme280_config *config, int32_t temp) {
12) * 12) *
((int32_t)params.dig_t3)) >> ((int32_t)params.dig_t3)) >>
14; 14;
int32_t var3 = var1 + var2; return var1 + var2;
// uses the BMP280 calibration parameters to compensate the temperature value }
// read from its registers
int32_t var4 = (var3 * 5 + 128) >> 8; float bme280_convert_temp(int32_t t_fine) {
return (float)var4 / 100; int32_t temp = (t_fine * 5 + 128) >> 8;
return (float)temp / 100;
}
float bmp280_convert_pressure(bme280_config *config, int32_t t_fine,
int32_t pressure) {
bme280_compensation_params params = config->params;
int32_t var1, var2;
uint32_t converted = 0.0;
var1 = (((int32_t)t_fine) >> 1) - (int32_t)64000;
var2 = (((var1 >> 2) * (var1 >> 2)) >> 11) * ((int32_t)params.dig_p6);
var2 += ((var1 * ((int32_t)params.dig_p5)) << 1);
var2 = (var2 >> 2) + (((int32_t)params.dig_p4) << 16);
var1 = (((params.dig_p3 * (((var1 >> 2) * (var1 >> 2)) >> 13)) >> 3) +
((((int32_t)params.dig_p2) * var1) >> 1)) >>
18;
var1 = ((((32768 + var1)) * ((int32_t)params.dig_p1)) >> 15);
if (var1 == 0) {
return 0; // avoid exception caused by division by zero
}
converted =
(((uint32_t)(((int32_t)1048576) - pressure) - (var2 >> 12))) * 3125;
if (converted < 0x80000000) {
converted = (converted << 1) / ((uint32_t)var1);
} else {
converted = (converted / (uint32_t)var1) * 2;
}
var1 = (((int32_t)params.dig_p9) *
((int32_t)(((converted >> 3) * (converted >> 3)) >> 13))) >>
12;
var2 = (((int32_t)(converted >> 2)) * ((int32_t)params.dig_p8)) >> 13;
converted =
(uint32_t)((int32_t)converted + ((var1 + var2 + params.dig_p7) >> 4));
return (float)converted / 100;
} }
bme280_reading bme280_read(bme280_config *config) { bme280_reading bme280_read(bme280_config *config) {
@ -206,8 +239,9 @@ bme280_reading bme280_read(bme280_config *config) {
int32_t raw_humidity = 0; int32_t raw_humidity = 0;
bme280_read_raw(config, &raw_temperature, &raw_pressure, &raw_humidity); bme280_read_raw(config, &raw_temperature, &raw_pressure, &raw_humidity);
bme280_reading reading; bme280_reading reading;
reading.temperature = bmp280_convert_temp(config, raw_temperature); int32_t t_fine = bme280_caculate_t_fine(config, raw_temperature);
reading.pressure = raw_pressure; reading.temperature = bme280_convert_temp(t_fine);
reading.pressure = bmp280_convert_pressure(config, t_fine, raw_pressure);
reading.humidity = raw_humidity; reading.humidity = raw_humidity;
return reading; return reading;
} }

2
bme280.h
View file

@ -33,7 +33,7 @@ typedef struct {
typedef struct { typedef struct {
float temperature; float temperature;
int32_t pressure; float pressure;
int32_t humidity; int32_t humidity;
} bme280_reading; } bme280_reading;

2
node1.c
View file

@ -15,7 +15,7 @@ int main() {
printf("Making reading\n"); printf("Making reading\n");
current_reading = bme280_read(&config); current_reading = bme280_read(&config);
printf("Tempature: %.2f\n", current_reading.temperature); printf("Tempature: %.2f\n", current_reading.temperature);
printf("Pressure: %d\n", current_reading.pressure); printf("Pressure: %.2f\n", current_reading.pressure);
printf("Humidity: %d\n", current_reading.humidity); printf("Humidity: %d\n", current_reading.humidity);
} }
} }