213 lines
7.5 KiB
C
213 lines
7.5 KiB
C
#include "bme280.h"
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#include "hardware/i2c.h"
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#include "pico/binary_info.h"
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#include "pico/stdlib.h"
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#include <stdint.h>
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#include <stdio.h>
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/*
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Lib for Bosh BME280 Env Sensor. To be used in weather station context.
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Sources:
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- pico example for bmp280 a simpler sensor then bme280 that does not
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include humidity
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https://github.com/raspberrypi/pico-examples/blob/master/i2c/bmp280_i2c/bmp280_i2c.c
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- bme280 datasheet
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https://cdn.shopify.com/s/files/1/0174/1800/files/bst-bme280-ds002.pdf?v=1662743150
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- bmp280 datasheet
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https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bmp280-ds001.pdf
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- pimoroni eshop
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https://shop.pimoroni.com/products/bme280-breakout?variant=29420960677971
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- pimoroni pico sdk
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https://github.com/boschsensortec/BME280_SensorAPI/tree/c47f06eb44fc96970f0abfcc941ec16425b2a9e6
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Suggested Settings:
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- forced mode at 1 sample per min
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- oversampling * 1 on temp, humidity, and pressure
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- IIR Filter off
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*/
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// Define the custom pins for I2C
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#define I2C_SDA_PIN 14 // Replace with your custom SDA pin
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#define I2C_SCL_PIN 15 // Replace with your custom SCL pin
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// Define the I2C instance to use (i2c0 or i2c1)
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#define I2C_PORT i2c1
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// device has default bus address of 0x76
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#define ADDR _u(0x76)
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// hardware registers
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#define REG_CONFIG _u(0xF5)
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#define REG_CTRL_MEAS _u(0xF4)
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// #define REG_RESET _u(0xE0)
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// #define REG_TEMP_XLSB _u(0xFC)
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// #define REG_TEMP_LSB _u(0xFB)
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// #define REG_TEMP_MSB _u(0xFA)
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// #define REG_PRESSURE_XLSB _u(0xF9)
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// #define REG_PRESSURE_LSB _u(0xF8)
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#define REG_PRESSURE_MSB _u(0xF7)
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// calibration registers
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#define REG_DIG_T1_LSB _u(0x88)
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// #define REG_DIG_T1_MSB _u(0x89)
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// #define REG_DIG_T2_LSB _u(0x8A)
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// #define REG_DIG_T2_MSB _u(0x8B)
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// #define REG_DIG_T3_LSB _u(0x8C)
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// #define REG_DIG_T3_MSB _u(0x8D)
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// #define REG_DIG_P1_LSB _u(0x8E)
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// #define REG_DIG_P1_MSB _u(0x8F)
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// #define REG_DIG_P2_LSB _u(0x90)
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// #define REG_DIG_P2_MSB _u(0x91)
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// #define REG_DIG_P3_LSB _u(0x92)
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// #define REG_DIG_P3_MSB _u(0x93)
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// #define REG_DIG_P4_LSB _u(0x94)
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// #define REG_DIG_P4_MSB _u(0x95)
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// #define REG_DIG_P5_LSB _u(0x96)
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// #define REG_DIG_P5_MSB _u(0x97)
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// #define REG_DIG_P6_LSB _u(0x98)
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// #define REG_DIG_P6_MSB _u(0x99)
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// #define REG_DIG_P7_LSB _u(0x9A)
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// #define REG_DIG_P7_MSB _u(0x9B)
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// #define REG_DIG_P8_LSB _u(0x9C)
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// #define REG_DIG_P8_MSB _u(0x9D)
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// #define REG_DIG_P9_LSB _u(0x9E)
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// #define REG_DIG_P9_MSB _u(0x9F)
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// number of calibration registers to be read
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// 17 * 2 = 34
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#define NUM_COMPENSATION_PARAMS 34
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static void bmp280_get_compensation_params(i2c_inst_t *i2c,
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bme280_compensation_params *params) {
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// raw temp and pressure values need to be calibrated according to
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// parameters generated during the manufacturing of the sensor
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// there are 3 temperature params, and 9 pressure params, each with a LSB
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// and MSB register, so we read from 24 registers
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uint8_t buf[NUM_COMPENSATION_PARAMS] = {0};
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uint8_t reg = REG_DIG_T1_LSB;
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i2c_write_blocking(i2c, ADDR, ®, 1,
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true); // true to keep master control of bus
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// read in one go as register addresses auto-increment
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i2c_read_blocking(i2c, ADDR, buf, NUM_COMPENSATION_PARAMS,
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false); // false, we're done reading
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// store these in a struct for later use
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params->dig_t1 = (uint16_t)(buf[1] << 8) | buf[0];
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params->dig_t2 = (int16_t)(buf[3] << 8) | buf[2];
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params->dig_t3 = (int16_t)(buf[5] << 8) | buf[4];
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params->dig_p1 = (uint16_t)(buf[7] << 8) | buf[6];
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params->dig_p2 = (int16_t)(buf[9] << 8) | buf[8];
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params->dig_p3 = (int16_t)(buf[11] << 8) | buf[10];
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params->dig_p4 = (int16_t)(buf[13] << 8) | buf[12];
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params->dig_p5 = (int16_t)(buf[15] << 8) | buf[14];
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params->dig_p6 = (int16_t)(buf[17] << 8) | buf[16];
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params->dig_p7 = (int16_t)(buf[19] << 8) | buf[18];
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params->dig_p8 = (int16_t)(buf[21] << 8) | buf[20];
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params->dig_p9 = (int16_t)(buf[23] << 8) | buf[22];
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params->dig_h1 = (int16_t)(buf[25] << 8) | buf[24];
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params->dig_h2 = (int16_t)(buf[27] << 8) | buf[26];
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params->dig_h3 = (int16_t)(buf[29] << 8) | buf[28];
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params->dig_h4 = (int16_t)(buf[31] << 8) | buf[30];
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params->dig_h5 = (int16_t)(buf[33] << 8) | buf[32];
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}
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// Main Config for the sensor. Defined here so it can be use to inital configure the sensor and to proc further reads
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// 001 sets osrs_t temp over sampling to 1, 001 sets osrs_p pressure
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// oversampling to 1, 01 sets sensor mode to forced
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static const uint8_t main_config = 0b00100101;
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void bme280_init(bme280_config *config, i2c_inst_t *i2c, uint8_t sda_pin,
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uint8_t scl_pin) {
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i2c_init(i2c, 100 * 1000);
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gpio_set_function(sda_pin, GPIO_FUNC_I2C);
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gpio_set_function(scl_pin, GPIO_FUNC_I2C);
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gpio_pull_up(sda_pin);
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gpio_pull_up(scl_pin);
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uint8_t buf[2];
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// 000 for t_sb is normal mode sample rate n/a, 000 turns filter off, 0 turns
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// off spi
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buf[0] = 0xF5; // config
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buf[1] = 0x00; // all zeros
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i2c_write_blocking(i2c, ADDR, buf, 2, false);
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// send humidity oversample config
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// 001 at the end sets over sampling to 1
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const uint8_t humidity_config = 0b00000001;
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buf[0] = 0xF2; // ctrl_hum
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buf[1] = humidity_config;
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i2c_write_blocking(i2c, ADDR, buf, 2, false);
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// send temp oversample, pressure oversample, and mode configs
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buf[0] = 0xF4; // ctrl_meas
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buf[1] = main_config;
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i2c_write_blocking(i2c, ADDR, buf, 2, false);
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bme280_compensation_params params;
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bmp280_get_compensation_params(i2c, ¶ms);
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config->params = params;
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config->i2c = i2c;
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return;
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}
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/**
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*Instructs the BME280 sensor to take a measurement in forced mode.
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*/
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static void bme280_proc_sensor_read(bme280_config *config) {
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uint8_t buf[2] = {0xF4, main_config};
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i2c_write_blocking(config->i2c, ADDR, buf, 2, false);
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}
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static void bme280_read_raw(bme280_config *config, int32_t *temp,
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int32_t *pressure, int32_t *humidity) {
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// TODO: burst read 0xF7 0xFE
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// pressure 20 bit, temp 20 bit, humidity 16 bit
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uint8_t buf[6];
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uint8_t reg = REG_PRESSURE_MSB;
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i2c_write_blocking(config->i2c, ADDR, ®, 1,
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true); // true to keep master control of bus
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i2c_read_blocking(config->i2c, ADDR, buf, 6,
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false); // false - finished with bus
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// store the 20 bit read in a 32 bit signed integer for conversion
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*pressure = (buf[0] << 12) | (buf[1] << 4) | (buf[2] >> 4);
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*temp = (buf[3] << 12) | (buf[4] << 4) | (buf[5] >> 4);
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}
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float bmp280_convert_temp(bme280_config *config, int32_t temp) {
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bme280_compensation_params params = config->params;
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int32_t var1, var2;
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var1 = ((((temp >> 3) - ((int32_t)params.dig_t1 << 1))) *
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((int32_t)params.dig_t2)) >>
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11;
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var2 = (((((temp >> 4) - ((int32_t)params.dig_t1)) *
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((temp >> 4) - ((int32_t)params.dig_t1))) >>
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12) *
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((int32_t)params.dig_t3)) >>
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14;
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int32_t var3 = var1 + var2;
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// uses the BMP280 calibration parameters to compensate the temperature value
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// read from its registers
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int32_t var4 = (var3 * 5 + 128) >> 8;
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return (float)var4 / 100;
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}
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bme280_reading bme280_read(bme280_config *config) {
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// instruct sensor to make a reading since we are in forced mode
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bme280_proc_sensor_read(config);
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int32_t raw_temperature = 0;
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int32_t raw_pressure = 0;
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int32_t raw_humidity = 0;
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bme280_read_raw(config, &raw_temperature, &raw_pressure, &raw_humidity);
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bme280_reading reading;
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reading.temperature = bmp280_convert_temp(config, raw_temperature);
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reading.pressure = raw_pressure;
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reading.humidity = raw_humidity;
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return reading;
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}
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