mhsw-espurna/code/espurna/sensors/BMX280Sensor.h

// -----------------------------------------------------------------------------
// BME280/BMP280 Sensor over I2C
// Uses SparkFun BME280 library
// Copyright (C) 2017 by Xose Pérez <xose dot perez at gmail dot com>
// -----------------------------------------------------------------------------

#pragma once

#include "Arduino.h"
#include "BaseSensor.h"
#include <SparkFunBME280.h>

#define BMX280_CHIP_BMP280          0x58
#define BMX280_CHIP_BME280          0x60

class BMX280Sensor : public BaseSensor {

    public:

        BMX280Sensor(unsigned char address = BMX280_ADDRESS): BaseSensor() {

            // Cache
            _address = address;
            _measurement_delay = bmeMeasurementTime();

            // Init
            bme = new BME280();
            bme->settings.commInterface = I2C_MODE;
            bme->settings.I2CAddress = _address;
            bme->settings.runMode = BMX280_MODE;
            bme->settings.tStandby = 0;
            bme->settings.filter = 0;
            bme->settings.tempOverSample = BMX280_TEMPERATURE;
            bme->settings.pressOverSample = BMX280_PRESSURE;
            bme->settings.humidOverSample = BMX280_HUMIDITY;

            // Fix when not measuring temperature, t_fine should have a sensible value
            if (BMX280_TEMPERATURE == 0) bme->t_fine = 100000; // aprox 20ºC

            // Make sure sensor had enough time to turn on. BMX280 requires 2ms to start up
            delay(10);

            // Check sensor correctly initialized
            _chip = bme->begin();
            if ((_chip != BMX280_CHIP_BME280) && (_chip != BMX280_CHIP_BMP280)) {
                _chip = 0;
                _error = SENSOR_ERROR_UNKNOWN_ID;
            }

            #if BMX280_TEMPERATURE > 0
                ++_count;
            #endif
            #if BMX280_PRESSURE > 0
                ++_count;
            #endif
            #if BMX280_HUMIDITY > 0
                if (_chip == BMX280_CHIP_BME280) ++_count;
            #endif

        }

        // Descriptive name of the sensor
        String name() {
            char buffer[20];
            snprintf(buffer, sizeof(buffer), "%s @ I2C (0x%02X)", _chip == BMX280_CHIP_BME280 ? "BME280" : "BMP280",  _address);
            return String(buffer);
        }

        // Descriptive name of the slot # index
        String slot(unsigned char index) {
            return name();
        }

        // Type for slot # index
        magnitude_t type(unsigned char index) {
            if (index < _count) {
                _error = SENSOR_ERROR_OK;
                unsigned char i = 0;
                #if BMX280_TEMPERATURE > 0
                    if (index == i++) return MAGNITUDE_TEMPERATURE;
                #endif
                #if BMX280_PRESSURE > 0
                    if (index == i++) return MAGNITUDE_PRESSURE;
                #endif
                #if BMX280_HUMIDITY > 0
                    if (_chip == BMX280_CHIP_BME280) {
                        if (index == i) return MAGNITUDE_HUMIDITY;
                    }
                #endif
            }
            _error = SENSOR_ERROR_OUT_OF_RANGE;
            return MAGNITUDE_NONE;
        }

        // Pre-read hook (usually to populate registers with up-to-date data)
        virtual void pre() {

            if (_chip == 0) {
                _error = SENSOR_ERROR_UNKNOWN_ID;
                return;
            }

            #if BMX280_MODE == 1
                bmeForceRead();
            #endif

        }

        // Current value for slot # index
        double value(unsigned char index) {

            if (index < _count) {
                _error = SENSOR_ERROR_OK;
                unsigned char i = 0;
                #if BMX280_TEMPERATURE > 0
                    if (index == i++) return bme->readTempC();
                #endif
                #if BMX280_PRESSURE > 0
                    if (index == i++) return bme->readFloatPressure() / 100;
                #endif
                #if BMX280_HUMIDITY > 0
                    if (_chip == BMX280_CHIP_BME280) {
                        if (index == i) return bme->readFloatHumidity();
                    }
                #endif
            }
            _error = SENSOR_ERROR_OUT_OF_RANGE;
            return 0;
        }

    protected:

        unsigned long bmeMeasurementTime() {

            // Measurement Time (as per BMX280 datasheet section 9.1)
            // T_max(ms) = 1.25
            //  + (2.3 * T_oversampling)
            //  + (2.3 * P_oversampling + 0.575)
            //  + (2.4 * H_oversampling + 0.575)
            //  ~ 9.3ms for current settings

            double t = 1.25;
            #if BMX280_TEMPERATURE > 0
                t += (2.3 * BMX280_TEMPERATURE);
            #endif
            #if BMX280_PRESSURE > 0
                t += (2.3 * BMX280_PRESSURE + 0.575);
            #endif
            #if BMX280_HUMIDITY > 0
                if (_chip == BMX280_CHIP_BME280) {
                    t += (2.4 * BMX280_HUMIDITY + 0.575);
                }
            #endif

            return round(t + 1); // round up

        }

        void bmeForceRead() {

            // We set the sensor in "forced mode" to force a reading.
            // After the reading the sensor will go back to sleep mode.
            uint8_t value = bme->readRegister(BME280_CTRL_MEAS_REG);
            value = (value & 0xFC) + 0x01;
            bme->writeRegister(BME280_CTRL_MEAS_REG, value);

            delay(_measurement_delay);

        }

        // ---------------------------------------------------------------------

        BME280 * bme;
        unsigned char _chip;
        unsigned char _address;
        unsigned long _measurement_delay;

};