SDS011.cpp

// SDS011 dust sensor PM2.5 and PM10
// ---------------------
//
// By R. Zschiegner (rz@madavi.de)
// April 2016
//
// Documentation:
//		- The iNovaFitness SDS011 datasheet
//


#include "SDS011.h"

// --------------------------------------------------------
// SDS011:read
// --------------------------------------------------------

SDS011::SDS011(void) {
}

int SDS011::read(float *p25, float *p10) {
	String s = "";
	char buffer;
	int value;
	int len = 0;
	int pm10_serial = 0;
	int pm25_serial = 0;
	int checksum_is;
	int checksum_ok = 0;
	int position = 0;
	int error = 1;
	while ((sds_data->available() > 0) && (sds_data->available() >= (10-len))) {
		buffer = sds_data->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 && checksum_ok == 1) {
			*p10 = pm10_serial/10;
			*p25 = pm25_serial/10;
			len = 0; checksum_ok = 0; pm10_serial = 0.0; pm25_serial = 0.0; checksum_is = 0;
			error = 0;
		}
		yield();
	}
	return error;
}

void SDS011::begin(uint8_t pin_rx, uint8_t pin_tx) {
	int error;
	uint8_t c;

  _pin_rx = pin_rx;
  _pin_tx = pin_tx;
  
	SoftwareSerial *softSerial = new SoftwareSerial(_pin_rx, _pin_tx);

	//Initialize the 'Wire' class for I2C-bus communication.
	softSerial->begin(9600);

	sds_data = softSerial;
}