mhsw-espurna/code/espurna/sensors/SDS011Sensor.h

// -----------------------------------------------------------------------------
// SDS011 particulates sensor
// Based on: https://github.com/ricki-z/SDS011
//
// Uses SoftwareSerial library
// Copyright (C) 2018 by Lucas Pleß <hello at lucas-pless dot com>
// -----------------------------------------------------------------------------

#if SENSOR_SUPPORT && SDS011_SUPPORT

#pragma once

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


class SDS011Sensor : public BaseSensor {

    public:

        // ---------------------------------------------------------------------
        // Public
        // ---------------------------------------------------------------------

        SDS011Sensor(): BaseSensor() {
            _count = 2;
            _sensor_id = SENSOR_SDS011_ID;
        }

        ~SDS011Sensor() {
            if (_serial) delete _serial;
        }

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

        void setRX(unsigned char pin_rx) {
            if (_pin_rx == pin_rx) return;
            _pin_rx = pin_rx;
            _dirty = true;
        }

        void setTX(unsigned char pin_tx) {
            if (_pin_tx == pin_tx) return;
            _pin_tx = pin_tx;
            _dirty = true;
        }

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

        unsigned char getRX() {
            return _pin_rx;
        }

        unsigned char getTX() {
            return _pin_tx;
        }

        // ---------------------------------------------------------------------
        // Sensor API
        // ---------------------------------------------------------------------

        // Initialization method, must be idempotent
        void begin() {

            if (!_dirty) return;

            if (_serial) delete _serial;

            _serial = new SoftwareSerial(_pin_rx, _pin_tx);
            _serial->begin(9600);

            _ready = true;
            _dirty = false;
        }

        // Descriptive name of the sensor
        String description() {
            char buffer[28];
            snprintf(buffer, sizeof(buffer), "SDS011 @ SwSerial(%u,%u)", _pin_rx, _pin_tx);
            return String(buffer);
        }

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

        // Address of the sensor (it could be the GPIO or I2C address)
        String address(unsigned char index) {
            char buffer[6];
            snprintf(buffer, sizeof(buffer), "%u:%u", _pin_rx, _pin_tx);
            return String(buffer);
        }

        // Type for slot # index
        unsigned char type(unsigned char index) {
            if (index == 0) return MAGNITUDE_PM2dot5;
            if (index == 1) return MAGNITUDE_PM10;
            return MAGNITUDE_NONE;
        }

        void pre() {
            _read();
        }

        // Current value for slot # index
        double value(unsigned char index) {
            if (index == 0) return _p2dot5;
            if (index == 1) return _p10;
            return 0;
        }



    protected:

        // ---------------------------------------------------------------------
        // Protected
        // ---------------------------------------------------------------------

        void _read() {
            byte buffer;
            int value;
            int len = 0;
            int pm10_serial = 0;
            int pm25_serial = 0;
            int checksum_is;
            int checksum_ok = 0;

            while ((_serial->available() > 0) && (_serial->available() >= (10-len))) {
                buffer = _serial->read();
                value = int(buffer);
                switch (len) {
                    case (0): if (value != 170) { len = -1; }; break;
                    case (1): if (value != 192) { len = -1; }; break;
                    case (2): pm25_serial = value; checksum_is = value; break;
                    case (3): pm25_serial += (value << 8); checksum_is += value; break;
                    case (4): pm10_serial = value; checksum_is += value; break;
                    case (5): pm10_serial += (value << 8); checksum_is += value; break;
                    case (6): checksum_is += value; break;
                    case (7): checksum_is += value; break;
                    case (8): if (value == (checksum_is % 256)) { checksum_ok = 1; } else { len = -1; }; break;
                    case (9): if (value != 171) { len = -1; }; break;
                }

                len++;

                if (len == 10) {
                    if(checksum_ok == 1) {
                        _p10 = (float)pm10_serial/10.0;
                        _p2dot5 = (float)pm25_serial/10.0;
                        len = 0; checksum_ok = 0; pm10_serial = 0.0; pm25_serial = 0.0; checksum_is = 0;
                        _error = SENSOR_ERROR_OK;
                    } else {
                        _error = SENSOR_ERROR_CRC;
                    }
                }

                yield();
            }

        }

        double _p2dot5 = 0;
        double _p10 = 0;
        unsigned int _pin_rx;
        unsigned int _pin_tx;
        SoftwareSerial * _serial = NULL;

};

#endif // SENSOR_SUPPORT && SDS011_SUPPORT