All files related to a toy air temp/humi/dust mointor based on DHT22, GP2Y1010AU0F, Arduino and Cubieboard (or Raspberry Pi).

air-graph-1d.timer

[Unit]
Description=Redraw air graphs.

[Timer]
OnBootSec=3min
OnUnitActiveSec=1h
Unit=air-graph@1d.service

[Install]
WantedBy=multi-user.target

air-graph-1m.timer

[Unit]
Description=Redraw air graphs.

[Timer]
OnBootSec=3min
OnUnitActiveSec=1d
Unit=air-graph@1m.service

[Install]
WantedBy=multi-user.target

air-graph-1w.timer

[Unit]
Description=Redraw air graphs.

[Timer]
OnBootSec=3min
OnUnitActiveSec=3h
Unit=air-graph@1w.service

[Install]
WantedBy=multi-user.target

air-graph@.service

[Unit]
Description=Execute a script to (re)draw RRD graphs once.

[Service]
Type=simple
User=xierch
Group=xierch
ExecStart=/home/xierch/arduino/graph.sh %i

arduino-uart.py

#!/usr/bin/env python3
from serial import Serial
import subprocess

RRDTOOL = '/usr/bin/rrdtool'
DATAFILE = '/home/xierch/arduino/data.rrd'
FORMAT = 'N:%d:%.1f:%d'

def readline(serial):
    line = serial.readline().decode().strip()
    return line

def read_block(serial):
    line = readline(serial)
    assert line == 'Dust'
    dust = int(readline(serial))

    line = readline(serial)
    assert line == 'Temp'
    temp = float(readline(serial))

    line = readline(serial)
    assert line == 'Humi'
    humi = float(readline(serial))
    humi = round(humi)

    handle_points(dust, temp, humi)


def handle_points(dust, temp, humi):
    print('%dmg %.1fC %d%%' % (dust, temp, humi))
    args = FORMAT % (dust, temp, humi)
    code = subprocess.call([RRDTOOL, 'update',
            '--daemon', '/tmp/rrdcached.sock',
            DATAFILE, args])
    if code != 0:
        print('rrdtool update failed.')


def main():
    serial = Serial(2)
    while True:
        read_block(serial)
    serial.close()

if __name__ == '__main__':
    main()

DHT22.cpp

/*
  DHT22.cpp - Library for DHT22/DHT11 relative humidity & temperature sensor.
  Created by Sorz. 2014-07-18.
*/
#include "Arduino.h"
#include "DHT22.h"

TempHumiSensor::TempHumiSensor(int pin)
{
  pinMode(pin, INPUT_PULLUP);
  _pin = pin;
}

byte TempHumiSensor::_getbyte()
{
  byte recv = 0;
  // Read eight bits. For each bit,
  // 0 is 26~28μs in high, 1 is 70μs in high.
  for (int i=7; i>=0; i--)
  {
    while (! digitalRead(_pin)); // Waiting for high.
    delayMicroseconds(50);
    recv |= digitalRead(_pin) << i;
    while (digitalRead(_pin)); // Waiting for the end of high.
  }
  return recv;
}

boolean TempHumiSensor::read(float *temp, float *humi)
{
  // Waits up IC.
  // 1. Pulldown at least 500μs, and pullup 20~40μs by host.
  // 2. Waiting for pulldown 80μs then pullup 80μs by DHT.
  pinMode(_pin, OUTPUT);
  digitalWrite(_pin, LOW);
  delay(10);
  pinMode(_pin, INPUT_PULLUP);
  delayMicroseconds(70); // (30 + 80) / 2, the middle of pulldown.
  boolean low = digitalRead(_pin);
  delayMicroseconds(80); // The middle of pullup.
  boolean high = digitalRead(_pin);
  delayMicroseconds(65); // 40 + 20 / 2, the middle of first byte lead.
  if (low != LOW || high != HIGH)
  {
    return false;
  }

  // Reads and checks.
  byte b[4];
  byte sum = 0; // Checksum
  for (int i=0; i<4; ++i)
  {
    b[i] = _getbyte();
    sum += b[i];
  }
  if (sum != _getbyte())
  {
    return false;
  }
  
  *humi = _decode_float(b[0], b[1]);
  *temp = _decode_float(b[2], b[3]);
  return true;
}

float TempHumiSensor::_decode_float(byte high, byte low)
{
  if (high < 128)
  {
    return (((word) high) << 8 | low) / 10.0;
  }
  else
  {
    return (((word) high - 128) << 8 | low) / -10.0;
  }
}

DHT22.h

/*
  DHT22.h - Library for DHT22 relative humidity & temperature sensor.
  Created by Sorz. 2014-07-17.
*/
#ifndef DHT22_h
#define DHT22_h

#include "Arduino.h"

class TempHumiSensor
{
  public:
    TempHumiSensor(int pin);
    boolean read(float *temp, float *humi);
  private:
    int _pin;
    byte _getbyte();
    float _decode_float(byte high, byte low);
};
#endif

GP2Y1010AU0F.cpp

/*
  GP2Y1010AU0F.cpp - Library for GP2Y1010AU0F Sharp dust sensor.
  Created by Sorz. 2014-07-17.
*/
#include "Arduino.h"
#include "GP2Y1010AU0F.h"

DustySensor::DustySensor(int ledPin, int outPin)
{
  pinMode(ledPin, OUTPUT);
  _ledPin = ledPin;
  _outPin = outPin;
}

int DustySensor::readRaw()
{
  digitalWrite(_ledPin, LOW); // Switch on LED.
  delayMicroseconds(280);
  int val = analogRead(_outPin);
  delayMicroseconds(40);
  digitalWrite(_ledPin,HIGH); // Switch off LED.
  delayMicroseconds(9680);
  return val;
}

int DustySensor::read()
{
  float volt = ((float) readRaw()) * 4.88281; // Voltage in mV.
  int mass = (int) (0.172 * volt - 0.9999); // Mass of dust in μg/m^3.
  return mass;
}
  

GP2Y1010AU0F.h

/*
  GP2Y1010AU0F.h - Library for GP2Y1010AU0F Sharp dust sensor.
  Created by Sorz. 2014-07-17.
*/
#ifndef GP2Y1010AU0F_h
#define GP2Y1010AU0F_h

#include "Arduino.h"

class DustySensor
{
  public:
    // ledPin - Digital pin connected to LED (#2) pin.
    // outPin - Analog pin connected to Vo (#5) pin.
    DustySensor(int ledPin, int outPin);
    // Returns mass of dust in μg/m^3.
    // The reference voltage must be 5V, otherwise the output is incorrect.
    int read();
    // Returns the raw value returned by analogRead().
    int readRaw();
  private:
    int _ledPin;
    int _outPin;
};

#endif

graph.sh

#!/bin/bash

DIR=/srv/http/home/air/graph
DATA=~/arduino/data.rrd
TIME=$1

time=$(date '+%H\:%M\:%S')

rrdtool graph $DIR/temp-$TIME.svg \
        --imgformat SVG \
        --start end-$TIME \
        --title "Air Temperature" \
        DEF:temp=$DATA:temp:AVERAGE \
        VDEF:avg=temp,AVERAGE \
        VDEF:max=temp,MAXIMUM \
        VDEF:min=temp,MINIMUM \
        VDEF:now=temp,LAST \
        LINE2:temp#d85427 \
        GPRINT:avg:"average\: %2.1lf℃" \
        GPRINT:max:"maximum\: %2.1lf℃" \
        GPRINT:min:"minimum\: %2.1lf℃" \
        GPRINT:now:"current\: %2.1lf℃" \
        COMMENT:"($time)"

rrdtool graph $DIR/humi-$TIME.svg \
        --imgformat SVG \
        --start end-$TIME \
        --title "Relative Humidity" \
        DEF:humi=$DATA:humi:AVERAGE \
        VDEF:avg=humi,AVERAGE \
        VDEF:max=humi,MAXIMUM \
        VDEF:min=humi,MINIMUM \
        VDEF:now=humi,LAST \
        LINE2:humi#0084a4 \
        GPRINT:avg:"average\: %2.0lf%%" \
        GPRINT:max:"maximum\: %2.0lf%%" \
        GPRINT:min:"minimum\: %2.0lf%%" \
        GPRINT:now:"current\: %2.0lf%%" \
        COMMENT:"($time)"

rrdtool graph $DIR/dust-$TIME.svg \
        --imgformat SVG \
        --start end-$TIME \
        --title "Dust Density" \
        DEF:dust=$DATA:dust:AVERAGE \
        VDEF:avg=dust,AVERAGE \
        VDEF:max=dust,MAXIMUM \
        VDEF:min=dust,MINIMUM \
        VDEF:now=dust,LAST \
        LINE2:dust#676767 \
        GPRINT:avg:"average\: %2.0lfµg/m³" \
        GPRINT:max:"maximum\: %2.0lfµg/m³" \
        GPRINT:min:"minimum\: %2.0lfµg/m³" \
        GPRINT:now:"current\: %2.0lfµg/m³" \
        COMMENT:"($time)"

index.html

<!doctype html>
<html lang="en-us">
  <head>
    <meta charset="utf-8" />
    <title>Air Quality at Home</title>
    <style>
      body { background: lightgray; }
      nav { text-align: center; color: gray; }
      nav a:link, nav a:visited { color: #555; }
      ul.graphs { list-style-type: none; text-align: center; }
      ul.graphs li { margin-bottom: 1em; }
      ul.graphs img { height: 249px; width: 641px; }
      footer p { text-align: right; color: darkgray; }
    </style>
  </head>
  <body>
    <nav>Time span:
      <a href="#1d">1d</a> |
      <a href="#1w">1w</a> |
      <a href="#1m">1m</a>
    </nav>
    <ul class="graphs">
      <li>
        <img data-name="temp" src="graph/temp-1d.svg" alt="Graph for temperature." />
      </li><li>
        <img data-name="humi" src="graph/humi-1d.svg" alt="Graph for humidity." />
      </li><li>
        <img data-name="dust" src="graph/dust-1d.svg" alt="Graph for dust density." />
      </li>
    </ul>
    <footer>
      <p>Data source: DHT22 (temperature &amp; humidity), GP2Y1010AU0F (dust).</p>
    </footer>
    <script src="https://code.jquery.com/jquery-2.1.3.min.js"></script>
    <script>
      $(document).ready(function () {
      });

      $(window).on('hashchange', function() {
        var time = (location.hash.replace(/^#/, "") || "1d");
        $('img').each(function () {
          var $img = $(this);
          var src = "graph/" + $img.data('name') + "-" + time + ".svg";
          console.log(src);
          $img.attr('src', src);
        });
      });
    </script>
  </body>
</html>

rrd-create.sh

#!/bin/bash

rrdtool create data.rrd --step 5 \
        DS:dust:GAUGE:10:0:600 \
        DS:temp:GAUGE:10:-40:80 \
        DS:humi:GAUGE:10:0:100 \
        RRA:AVERAGE:0.5:12:12960 \
        RRA:AVERAGE:0.5:60:25920 \
        RRA:AVERAGE:0.5:360:35040

rrdupdate-air.service

[Unit]
Description=Run rrdupdate for air data collecting.

[Service]
Type=simple
ExecStart=/home/xierch/arduino/arduino-uart.py
Restart=always
RestartSec=60

[Install]
WantedBy=multi-user.target

Sensors.ino

#include "GP2Y1010AU0F.h"
#include "DHT22.h"

DustySensor dustSensor(10, 0);
TempHumiSensor tempHumiSensor(9);

void setup(){
  Serial.begin(9600);
}

void loop(){
  int dustVal = dustSensor.read();
  Serial.println("Dust");
  Serial.println(dustVal);
  float temp = 0;
  float humi = 0;
  tempHumiSensor.read(&temp, &humi);
  Serial.println("Temp");
  Serial.println(temp);
  Serial.println("Humi");  
  Serial.println(humi);
  delay(3000);
}