SDS011-select-serial.cpp

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

#include "SDS011-select-serial.h"

static const byte SLEEPCMD[19] = {
	0xAA,	// head
	0xB4,	// command id
	0x06,	// data byte 1
	0x01,	// data byte 2 (set mode)
	0x00,	// data byte 3 (sleep)
	0x00,	// data byte 4
	0x00,	// data byte 5
	0x00,	// data byte 6
	0x00,	// data byte 7
	0x00,	// data byte 8
	0x00,	// data byte 9
	0x00,	// data byte 10
	0x00,	// data byte 11
	0x00,	// data byte 12
	0x00,	// data byte 13
	0xFF,	// data byte 14 (device id byte 1)
	0xFF,	// data byte 15 (device id byte 2)
	0x05,	// checksum
	0xAB	// tail
};

SDS011::SDS011(Stream& serial):
sds_data(serial) {}

// --------------------------------------------------------
// SDS011:read
// --------------------------------------------------------
int SDS011::read(float *p25, float *p10) {
	byte buffer;
	int value;
	int len = 0;
	int pm10_serial = 0;
	int pm25_serial = 0;
	int checksum_is;
	int checksum_ok = 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 = (float)pm10_serial/10.0;
			*p25 = (float)pm25_serial/10.0;
			len = 0; checksum_ok = 0; pm10_serial = 0.0; pm25_serial = 0.0; checksum_is = 0;
			error = 0;
		}
		yield();
	}
	return error;
}

// --------------------------------------------------------
// SDS011:sleep
// --------------------------------------------------------
void SDS011::sleep() {
	for (uint8_t i = 0; i < 19; i++) {
		sds_data.write(SLEEPCMD[i]);
	}
	sds_data.flush();
	while (sds_data.available() > 0) {
		sds_data.read();
	}
}

// --------------------------------------------------------
// SDS011:wakeup
// --------------------------------------------------------
void SDS011::wakeup() {
	sds_data.write(0x01);
	sds_data.flush();
}