/*
* The MySensors Arduino library handles the wireless radio link and protocol
* between your home built sensors/actuators and HA controller of choice.
* The sensors forms a self healing radio network with optional repeaters. Each
* repeater and gateway builds a routing tables in EEPROM which keeps track of the
* network topology allowing messages to be routed to nodes.
*
* Created by Henrik Ekblad 
* Copyright (C) 2013-2015 Sensnology AB
* Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
*
* Documentation: http://www.mysensors.org
* Support Forum: http://forum.mysensors.org
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* version 2 as published by the Free Software Foundation.
*
*******************************
*
* DESCRIPTION
*
* MH-Z19 CO2 sensor
*
* It communicates with your board over serial at 9600 speed.
*
*
*
*/


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

// if you uncomment this, you can get test and debug updates about the sensor' wireless connection by using the serial monitor tool.
#define MY_DEBUG

// Enable and select radio type attached
#define MY_RADIO_NRF24 // A 2.4Ghz transmitter and receiver, often used with MySensors.
// #define MY_RF24_PA_LEVEL RF24_PA_MIN // This sets a low-power mode for the radio. Useful if you use the verison with the bigger antenna, but don't want to power that from a separate power source. It can also fix problems with fake Chinese versions of the radio.
// #define MY_RADIO_RFM69 // 433Mhz transmitter and reveiver.

// Choose if you want this sensor to also be a repeater.
// #define MY_REPEATER_FEATURE // Just remove the two slashes at the beginning of this line to also enable this sensor to act as a repeater for other sensors. If this node is on battery power, you probably shouldn't enable this.


// Libraries
#include 
#include 


// This can be changed:
unsigned long co2MeasurementInterval = 30000; // Time to wait between reads (in milliseconds).
SoftwareSerial mySerial(10, 11); // RX, TX . You can choose other pins if you prefer.


// Mysensors settings
#define CHILD_ID_CO2 0 // The Co2 sensor' ID on this node.
MyMessage msgCo2(CHILD_ID_CO2, V_LEVEL);
MyMessage msgCo2b(CHILD_ID_CO2, V_UNIT_PREFIX);


void presentation()
{
// Send the sketch version information to the gateway and Controller
sendSketchInfo("AIQ Sensor CO2 MH-Z19", "1.1");

// Register attached sensor(s) to gateway
present(CHILD_ID_CO2, S_AIR_QUALITY);
send(msgCo2b.set("ppm"));
}


void setup()
{
delay(1000);
Serial.begin(115200);
delay(1000);

mySerial.begin(9600);
delay(2000);
while (mySerial.read()!=-1) {}; //clear Co2 buffer.
Serial.println("hello world, I am a sensor.");
}


void loop()
{

// You should not change these variables:
static unsigned long previousCo2Millis = 0; // Used to remember the time of the last temperature measurement.

unsigned long currentMillis = millis(); // The time since the sensor started, counted in milliseconds. This script tries to avoid using the Sleep function, so that it could at the same time be a MySensors repeater.

if (currentMillis - previousCo2Millis >= co2MeasurementInterval) { // this only gets triggered when enough time has passed.
Serial.println("CO2 - Sending data request to sensor.");
previousCo2Millis = currentMillis;

long co2ppm = readCO2();
Serial.println("Co2 - PPM = " + String(co2ppm));
send(msgCo2.set((long)ceil(co2ppm)));
Serial.print("Co2 - zzzzZZZZzzzzZZZZzzzz\n");
}

}


// Main function that gets the Co2 data
int readCO2()
{
while (mySerial.read()!=-1) {}; //clear serial buffer 

char response[9]; // for answer
byte cmd[9] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};

// command to ask for data
mySerial.write(cmd, 9); //request PPM CO2 

mySerial.readBytes(response, 9);

Serial.print(response[0], HEX);
Serial.print(" - ");
Serial.print(response[1], HEX);
Serial.print(" - ");
Serial.print(response[2], HEX);
Serial.print(" - ");
Serial.print(response[3], HEX);
Serial.print(" - ");
Serial.print(response[4], HEX);
Serial.print(" - ");
Serial.print(response[5], HEX);
Serial.print(" - ");
Serial.print(response[6], HEX);
Serial.print(" - ");
Serial.print(response[7], HEX);
Serial.print(" - ");
Serial.print(response[8], HEX);
Serial.println(" - END");

if (response[0] != 0xFF)
{
Serial.println("Wrong starting byte from co2 sensor! (should be FF)");
return -1;
}

if (response[1] != 0x86)
{
Serial.println("Wrong command from co2 sensor! (should be 86)");
return -1;
}

int responseHigh = (int) response[2];
int responseLow = (int) response[3];
int ppm = (256 * responseHigh) + responseLow;

return ppm;
}

MH-Z19B carbon dioxide gas sensor (hereinafter referred to as the sensor) is a general-purpose smart small-scale sensor that uses non-dispersive infrared (NDIR) principle to detect the presence of CO2 in the air, with good selectivity and anaerobic  Gas dependence, long life and other characteristics; built-in temperature compensation; at the same time with serial output, analog output and PWM output, easy to use. The sensor is a high-performance sensor that combines mature infrared absorption gas detection technology with precise optical path design and sophisticated circuit design.

Parameters:

• Product model number: MH-Z19B
• Gas Detection: Carbon Dioxide
• Supply voltage: 4.5~5.5V DC
• Average current: <20mA (@5V power supply)
• Peak current: 150 mA (@5V supply)
• Interface level: 3.3V (5V compatible)
• Measurement range: 0~10000ppm can be selected within the range
• Warm-up time: 3min
• Response time: T90<120s
• Working temperature: 0～50°C
• Operating Humidity: 0 to 95% RH (non-condensing)