Arduino Nano Using Median Filter to Display DHT22 and RTC

Despike/smooth data from a DHT22 with a median filter and display on a 0.96 inch OLED with the date and time from a DS3231 real-time clock!

Feb 28, 2020

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weather

clocks

data collection

Components and supplies

DHT22 Temperature Sensor

Robojax DS3231 IIC Precision Real time Clock Module

Kuman 0.96 Inch Yellow Blue IIC OLED Module I2c

Arduino Nano R3

Project description

Code

DHT Median filter with RTC

arduino

Simply upload to your Nano with the Arduini IDE

1/*
2 
3  Use an Arduino Nano to display temp/humidy on 0.96 inch Yellow/Blue  IIC OLED I2c 
4  serial 128x64 Display
5  
6  Use an Adafruit DHT22 Temperature  and Humidity Sensor (accuracy ±2%)
7
8  These data might bounce around somewhat  because the sensor can be a little noisy
9  at times.  We use a simple median  filter to smooth out the noise
10  
11  Arduino Nano <--> OLED = pin A4 to SDA  and pin A5 to SLC 
12
13  February 2020
14
15  Paul M Dunphy, VE1DX
16  
17*/
18
19
20//  This library allows you to communicate with I2C devices, in this
21// case the  RTC and OLED display
22#include <Wire.h> 
23
24// For the DS3231 Real time Clock  Module (AT24C32 Module)
25#include <DS1307RTC.h>
26
27// Include DHT Library  from Adafruit
28
29#include "DHT.h";
30/* DHT22 pin-out:
31   Pin 1 VCC 
32   Pin 2 Data out
33   Pin 3 Not connected
34   Pin 4 Ground
35*/
36
37#include  "U8glib.h"  // For the OLED - Obtain from: https://github.com/olikraus/u8glib
38
39//  Define Constants
40 
41#define dhtPin 7        // DHT-22 Output Pin connection
42#define  dhtType DHT22   // DHT Type is a DHT 22 (AM2302)
43
44// Initialize OLED
45U8GLIB_SSD1306_128X32  u8g(U8G_I2C_OPT_NONE);
46
47// Initialize DHT sensor
48 
49DHT dht(dhtPin, dhtType);  
50
51tmElements_t tm;  // For the RTC
52
53#define buff_size 7  // Must be  an odd number.  Should be greater than 5.  7 works well.
54
55unsigned long a_second  = 1000;
56float h = 0.0;  //Stores humidity value
57float t = 0.0;  //Stores temperature  value
58float h_array[buff_size] = {0.0};
59float t_array[buff_size] = {0.0};
60float  h_array_sort[buff_size] = {0.0};
61float t_array_sort[buff_size] = {0.0};
62String  string_Temp, string_Humid, temporary_string, tick_string;
63
64 
65char OLED_string_1[50];  // Need a couple of character buffers to hold the two OLED lines
66char OLED_string_2[50];
67
68
69String  str_day, str_month, str_year, str_time; // Lot of conversion to strings required  because the
70                                               // DSD Tech display  doesn't like integers and floats
71
72
73void clearOLED()
74  {
75    u8g.firstPage();  
76    do {
77    } while( u8g.nextPage() );
78  }
79
80
81void Initialize()
82{
83  float startup_delay;
84  int i;
85  
86  clearOLED();
87  startup_delay =  buff_size * (a_second * 5.0 / 1000.0);
88  temporary_string  = String(startup_delay,0);
89  temporary_string = " (" + temporary_string + " seconds)";
90
91  tick_string  = "Initializing "; 
92  strcpy(OLED_string_1, tick_string.c_str());
93  strcpy(OLED_string_2,  temporary_string.c_str());
94  
95  // Take "buff_size" readings of each parameter,  one every 5 seconds,
96  // to get initial arrays of data.  Print "status" dots  across display.
97  for (i = 0 ; i < buff_size ; i++)
98    {    
99       tick_string  = tick_string + ". ";
100       strcpy(OLED_string_1, tick_string.c_str());
101       sendstringstoDisplay();
102       delay(a_second * 5);
103       h_array[i]  = dht.readHumidity();       // Get Humidity value
104       t_array[i] = dht.readTemperature();    // Get Temperature value
105    }    
106  }
107
108
109
110void bubble_sort(float  sort_array[], int n)
111  {
112  int i, j;
113  float  temp;
114 
115  for (i =  0 ; i < n - 1; i++)
116    {
117      for (j = 0 ; j < n - i - 1; j++)
118        {
119          if (sort_array[j] > sort_array[j+1])
120            {
121            //  Swap values 
122            temp            = sort_array[j];
123            sort_array[j]   = sort_array[j+1];
124            sort_array[j+1] = temp;
125            }
126          }
127      }
128  }
129
130
131
132
133void sendstringstoDisplay()
134  {
135    u8g.firstPage();  // Send them to the dispaly
136      do {
137
138        u8g.setFont(u8g_font_5x7);  // This can be adjusted to various fonts.  See:  https://github.com/olikraus/u8glib/wiki/fontsize
139        u8g.setPrintPos(0,7);       // Position of first line
140        u8g.print(OLED_string_1);
141        u8g.setFont(u8g_font_helvB14); // Little biger and bolder font as this is  the temperature and humidy
142        u8g.setPrintPos(0, 25);        // Position  of second line
143        u8g.print(OLED_string_2);
144
145         } while (u8g.nextPage()  );
146  }
147
148
149
150
151void monthStr(tmElements_t tm)
152{
153
154   int int_month;
155   
156   str_month = tm.Month;
157   int_month = str_month.toInt();
158
159   switch(int_month)
160   {
161   case 1:
162         str_month =("JAN");
163         break;
164   case  2:
165         str_month =("FEB");
166         break;
167   case 3:
168         str_month  =("MAR");
169         break;
170   case 4:
171         str_month =("APR");
172         break;
173   case 5:
174         str_month =("MAY");
175         break;
176   case 6:
177         str_month =("JUN");
178         break;
179   case 7:
180         str_month =("JUL");
181         break;
182   case 8:
183         str_month  =("AUG");
184         break;
185   case 9:
186         str_month =("SEP");
187         break;
188   case 10:
189         str_month =("OCT");
190         break;
191   case 11:
192         str_month =("NOV");
193         break;
194   case 12:
195         str_month =("DEC");
196         break;
197   default:
198         str_month  =("ERR");
199         break;
200      }
201      
202}
203
204
205
206void timeStr(tmElements_t  tm)
207{
208
209  // Add a leading zero when needed so all numbers are two characters
210   
211  String hours,seconds,minutes;
212
213  if(tm.Hour<10)
214  {
215    hours  = "0"+String(tm.Hour);
216  }
217  else
218  { 
219    hours = String(tm.Hour);  
220   }
221  
222  if(tm.Minute<10)
223  {
224    minutes = "0"+String(tm.Minute);
225  }
226  else
227  { 
228    minutes = String(tm.Minute); 
229   }
230
231  // We're  processing seconds "just in case", but not adding them to the small display 
232  
233  if(tm.Second<10)
234  {
235    seconds = "0"+String(tm.Second);
236  }
237  else
238  { 
239    seconds = String(tm.Second); 
240   }
241   
242  str_time  = hours + ":" + minutes;
243}
244  
245
246
247
248void setup() 
249  { 
250   //  Start Wire library for I2C
251   Wire.begin();  
252   clearOLED();  
253   dht.begin();
254   // initialize digital pin LED_BUILTIN as an output.
255   pinMode(LED_BUILTIN,  OUTPUT); 
256   Initialize();
257  } 
258
259
260
261
262void loop()
263  { 
264    int i, median_index;
265    
266    RTC.read(tm);  // Get the date and time
267    monthStr(tm);  // Convert the month from a number to Jan, Feb, Mar, etc
268    timeStr(tm);   // Convert the time to strings
269
270    h = dht.readHumidity();         // Get Humidity value
271    t = dht.readTemperature();      // Get Temperature  value
272
273    // Replace the oldest value with the newest just read by moving  every element in 
274    // the arrays up one and sticking this new value in the  bottom.
275    for (i = 0 ; i < buff_size - 1 ; i++)
276      {   
277        h_array[i]  = h_array[i + 1];
278        t_array[i] = t_array[i + 1];
279      }
280    h_array[buff_size-1]  = h;
281    t_array[buff_size-1] = t;
282
283    // Move them into the sort arrays
284    for (i = 0 ; i < buff_size ; i++)
285      {    
286        h_array_sort[i]  = h_array[i];
287        t_array_sort[i] = t_array[i];
288      }
289
290    //  Sort them. Use quick and dirty bubble sort because it's a small number of data points
291    bubble_sort(h_array_sort, buff_size);
292    bubble_sort(t_array_sort, buff_size);
293
294    // Use the median of the last "buff_zize" readings for the display
295    median_index  = buff_size / 2;
296    h = h_array_sort[median_index]; 
297    t = t_array_sort[median_index];
298    string_Temp  = String(t,1);     // Make temp a character string
299    string_Humid  = String(h,1);     // Make humid a character string
300    
301    //  Build first  OLED line
302    str_year = tmYearToCalendar(tm.Year);
303    str_day = tm.Day;
304    str_day = str_day + "-";
305    str_month = str_month + "-";
306    temporary_string  = "    " + str_day + str_month + str_year + " " + str_time;
307    strcpy(OLED_string_1,  temporary_string.c_str());      // Put date/time string in the first character array
308    
309    //  Build second OLED line
310    temporary_string = "";
311    temporary_string  = temporary_string + string_Temp + char(176) + "C   ";  // char(176) is the degree  symbol
312    temporary_string = temporary_string + string_Humid + " %";    
313    strcpy(OLED_string_2, temporary_string.c_str());      // Put temperature/humidity  string in the second character array
314    
315    
316    sendstringstoDisplay();             // Display the median temperature and humidity
317    delay(5000);                        // Updates every 5 seconds
318  
319  }

/*
 
  Use an Arduino Nano to display temp/humidy on 0.96 inch Yellow/Blue  IIC OLED I2c 
  serial 128x64 Display
  
  Use an Adafruit DHT22 Temperature  and Humidity Sensor (accuracy ±2%)

  These data might bounce around somewhat  because the sensor can be a little noisy
  at times.  We use a simple median  filter to smooth out the noise
  
  Arduino Nano <--> OLED = pin A4 to SDA  and pin A5 to SLC 

  February 2020

  Paul M Dunphy, VE1DX
  
*/


//  This library allows you to communicate with I2C devices, in this
// case the  RTC and OLED display
#include <Wire.h> 

// For the DS3231 Real time Clock  Module (AT24C32 Module)
#include <DS1307RTC.h>

// Include DHT Library  from Adafruit

#include "DHT.h";
/* DHT22 pin-out:
   Pin 1 VCC 
   Pin 2 Data out
   Pin 3 Not connected
   Pin 4 Ground
*/

#include  "U8glib.h"  // For the OLED - Obtain from: https://github.com/olikraus/u8glib

//  Define Constants
 
#define dhtPin 7        // DHT-22 Output Pin connection
#define  dhtType DHT22   // DHT Type is a DHT 22 (AM2302)

// Initialize OLED
U8GLIB_SSD1306_128X32  u8g(U8G_I2C_OPT_NONE);

// Initialize DHT sensor
 
DHT dht(dhtPin, dhtType);  

tmElements_t tm;  // For the RTC

#define buff_size 7  // Must be  an odd number.  Should be greater than 5.  7 works well.

unsigned long a_second  = 1000;
float h = 0.0;  //Stores humidity value
float t = 0.0;  //Stores temperature  value
float h_array[buff_size] = {0.0};
float t_array[buff_size] = {0.0};
float  h_array_sort[buff_size] = {0.0};
float t_array_sort[buff_size] = {0.0};
String  string_Temp, string_Humid, temporary_string, tick_string;

 
char OLED_string_1[50];  // Need a couple of character buffers to hold the two OLED lines
char OLED_string_2[50];


String  str_day, str_month, str_year, str_time; // Lot of conversion to strings required  because the
                                               // DSD Tech display  doesn't like integers and floats


void clearOLED()
  {
    u8g.firstPage();  
    do {
    } while( u8g.nextPage() );
  }


void Initialize()
{
  float startup_delay;
  int i;
  
  clearOLED();
  startup_delay =  buff_size * (a_second * 5.0 / 1000.0);
  temporary_string  = String(startup_delay,0);
  temporary_string = " (" + temporary_string + " seconds)";

  tick_string  = "Initializing "; 
  strcpy(OLED_string_1, tick_string.c_str());
  strcpy(OLED_string_2,  temporary_string.c_str());
  
  // Take "buff_size" readings of each parameter,  one every 5 seconds,
  // to get initial arrays of data.  Print "status" dots  across display.
  for (i = 0 ; i < buff_size ; i++)
    {    
       tick_string  = tick_string + ". ";
       strcpy(OLED_string_1, tick_string.c_str());
       sendstringstoDisplay();
       delay(a_second * 5);
       h_array[i]  = dht.readHumidity();       // Get Humidity value
       t_array[i] = dht.readTemperature();    // Get Temperature value
    }    
  }



void bubble_sort(float  sort_array[], int n)
  {
  int i, j;
  float  temp;
 
  for (i =  0 ; i < n - 1; i++)
    {
      for (j = 0 ; j < n - i - 1; j++)
        {
          if (sort_array[j] > sort_array[j+1])
            {
            //  Swap values 
            temp            = sort_array[j];
            sort_array[j]   = sort_array[j+1];
            sort_array[j+1] = temp;
            }
          }
      }
  }




void sendstringstoDisplay()
  {
    u8g.firstPage();  // Send them to the dispaly
      do {

        u8g.setFont(u8g_font_5x7);  // This can be adjusted to various fonts.  See:  https://github.com/olikraus/u8glib/wiki/fontsize
        u8g.setPrintPos(0,7);       // Position of first line
        u8g.print(OLED_string_1);
        u8g.setFont(u8g_font_helvB14); // Little biger and bolder font as this is  the temperature and humidy
        u8g.setPrintPos(0, 25);        // Position  of second line
        u8g.print(OLED_string_2);

         } while (u8g.nextPage()  );
  }




void monthStr(tmElements_t tm)
{

   int int_month;
   
   str_month = tm.Month;
   int_month = str_month.toInt();

   switch(int_month)
   {
   case 1:
         str_month =("JAN");
         break;
   case  2:
         str_month =("FEB");
         break;
   case 3:
         str_month  =("MAR");
         break;
   case 4:
         str_month =("APR");
         break;
   case 5:
         str_month =("MAY");
         break;
   case 6:
         str_month =("JUN");
         break;
   case 7:
         str_month =("JUL");
         break;
   case 8:
         str_month  =("AUG");
         break;
   case 9:
         str_month =("SEP");
         break;
   case 10:
         str_month =("OCT");
         break;
   case 11:
         str_month =("NOV");
         break;
   case 12:
         str_month =("DEC");
         break;
   default:
         str_month  =("ERR");
         break;
      }
      
}



void timeStr(tmElements_t  tm)
{

  // Add a leading zero when needed so all numbers are two characters
   
  String hours,seconds,minutes;

  if(tm.Hour<10)
  {
    hours  = "0"+String(tm.Hour);
  }
  else
  { 
    hours = String(tm.Hour);  
   }
  
  if(tm.Minute<10)
  {
    minutes = "0"+String(tm.Minute);
  }
  else
  { 
    minutes = String(tm.Minute); 
   }

  // We're  processing seconds "just in case", but not adding them to the small display 
  
  if(tm.Second<10)
  {
    seconds = "0"+String(tm.Second);
  }
  else
  { 
    seconds = String(tm.Second); 
   }
   
  str_time  = hours + ":" + minutes;
}
  



void setup() 
  { 
   //  Start Wire library for I2C
   Wire.begin();  
   clearOLED();  
   dht.begin();
   // initialize digital pin LED_BUILTIN as an output.
   pinMode(LED_BUILTIN,  OUTPUT); 
   Initialize();
  } 




void loop()
  { 
    int i, median_index;
    
    RTC.read(tm);  // Get the date and time
    monthStr(tm);  // Convert the month from a number to Jan, Feb, Mar, etc
    timeStr(tm);   // Convert the time to strings

    h = dht.readHumidity();         // Get Humidity value
    t = dht.readTemperature();      // Get Temperature  value

    // Replace the oldest value with the newest just read by moving  every element in 
    // the arrays up one and sticking this new value in the  bottom.
    for (i = 0 ; i < buff_size - 1 ; i++)
      {   
        h_array[i]  = h_array[i + 1];
        t_array[i] = t_array[i + 1];
      }
    h_array[buff_size-1]  = h;
    t_array[buff_size-1] = t;

    // Move them into the sort arrays
    for (i = 0 ; i < buff_size ; i++)
      {    
        h_array_sort[i]  = h_array[i];
        t_array_sort[i] = t_array[i];
      }

    //  Sort them. Use quick and dirty bubble sort because it's a small number of data points
    bubble_sort(h_array_sort, buff_size);
    bubble_sort(t_array_sort, buff_size);

    // Use the median of the last "buff_zize" readings for the display
    median_index  = buff_size / 2;
    h = h_array_sort[median_index]; 
    t = t_array_sort[median_index];
    string_Temp  = String(t,1);     // Make temp a character string
    string_Humid  = String(h,1);     // Make humid a character string
    
    //  Build first  OLED line
    str_year = tmYearToCalendar(tm.Year);
    str_day = tm.Day;
    str_day = str_day + "-";
    str_month = str_month + "-";
    temporary_string  = "    " + str_day + str_month + str_year + " " + str_time;
    strcpy(OLED_string_1,  temporary_string.c_str());      // Put date/time string in the first character array
    
    //  Build second OLED line
    temporary_string = "";
    temporary_string  = temporary_string + string_Temp + char(176) + "C   ";  // char(176) is the degree  symbol
    temporary_string = temporary_string + string_Humid + " %";    
    strcpy(OLED_string_2, temporary_string.c_str());      // Put temperature/humidity  string in the second character array
    
    
    sendstringstoDisplay();             // Display the median temperature and humidity
    delay(5000);                        // Updates every 5 seconds
  
  }

DHT Median filter with RTC

arduino

Simply upload to your Nano with the Arduini IDE

1/*
2 
3  Use an Arduino Nano to display temp/humidy on 0.96 inch Yellow/Blue
4  IIC OLED I2c 
5  serial 128x64 Display
6  
7  Use an Adafruit DHT22 Temperature
8  and Humidity Sensor (accuracy ±2%)
9
10  These data might bounce around somewhat
11  because the sensor can be a little noisy
12  at times.  We use a simple median
13  filter to smooth out the noise
14  
15  Arduino Nano <--> OLED = pin A4 to SDA
16  and pin A5 to SLC 
17
18  February 2020
19
20  Paul M Dunphy, VE1DX
21  
22*/
23
24
25//
26  This library allows you to communicate with I2C devices, in this
27// case the
28  RTC and OLED display
29#include <Wire.h> 
30
31// For the DS3231 Real time Clock
32  Module (AT24C32 Module)
33#include <DS1307RTC.h>
34
35// Include DHT Library
36  from Adafruit
37
38#include "DHT.h";
39/* DHT22 pin-out:
40   Pin 1 VCC 
41
42   Pin 2 Data out
43   Pin 3 Not connected
44   Pin 4 Ground
45*/
46
47#include
48  "U8glib.h"  // For the OLED - Obtain from: https://github.com/olikraus/u8glib
49
50//
51  Define Constants
52 
53#define dhtPin 7        // DHT-22 Output Pin connection
54#define
55  dhtType DHT22   // DHT Type is a DHT 22 (AM2302)
56
57// Initialize OLED
58U8GLIB_SSD1306_128X32
59  u8g(U8G_I2C_OPT_NONE);
60
61// Initialize DHT sensor
62 
63DHT dht(dhtPin, dhtType);
64  
65
66tmElements_t tm;  // For the RTC
67
68#define buff_size 7  // Must be
69  an odd number.  Should be greater than 5.  7 works well.
70
71unsigned long a_second
72  = 1000;
73float h = 0.0;  //Stores humidity value
74float t = 0.0;  //Stores temperature
75  value
76float h_array[buff_size] = {0.0};
77float t_array[buff_size] = {0.0};
78float
79  h_array_sort[buff_size] = {0.0};
80float t_array_sort[buff_size] = {0.0};
81String
82  string_Temp, string_Humid, temporary_string, tick_string;
83
84 
85char OLED_string_1[50];
86  // Need a couple of character buffers to hold the two OLED lines
87char OLED_string_2[50];
88
89
90String
91  str_day, str_month, str_year, str_time; // Lot of conversion to strings required
92  because the
93                                               // DSD Tech display
94  doesn't like integers and floats
95
96
97void clearOLED()
98  {
99    u8g.firstPage();
100  
101    do {
102    } while( u8g.nextPage() );
103  }
104
105
106void Initialize()
107{
108
109  float startup_delay;
110  int i;
111  
112  clearOLED();
113  startup_delay =
114  buff_size * (a_second * 5.0 / 1000.0);
115  temporary_string  = String(startup_delay,0);
116
117  temporary_string = " (" + temporary_string + " seconds)";
118
119  tick_string
120  = "Initializing "; 
121  strcpy(OLED_string_1, tick_string.c_str());
122  strcpy(OLED_string_2,
123  temporary_string.c_str());
124  
125  // Take "buff_size" readings of each parameter,
126  one every 5 seconds,
127  // to get initial arrays of data.  Print "status" dots
128  across display.
129  for (i = 0 ; i < buff_size ; i++)
130    {    
131       tick_string
132  = tick_string + ". ";
133       strcpy(OLED_string_1, tick_string.c_str());
134
135       sendstringstoDisplay();
136       delay(a_second * 5);
137       h_array[i]
138  = dht.readHumidity();       // Get Humidity value
139       t_array[i] = dht.readTemperature();
140    // Get Temperature value
141    }    
142  }
143
144
145
146void bubble_sort(float
147  sort_array[], int n)
148  {
149  int i, j;
150  float  temp;
151 
152  for (i =
153  0 ; i < n - 1; i++)
154    {
155      for (j = 0 ; j < n - i - 1; j++)
156        {
157
158          if (sort_array[j] > sort_array[j+1])
159            {
160            //
161  Swap values 
162            temp            = sort_array[j];
163            sort_array[j]
164   = sort_array[j+1];
165            sort_array[j+1] = temp;
166            }
167
168          }
169      }
170  }
171
172
173
174
175void sendstringstoDisplay()
176
177  {
178    u8g.firstPage();  // Send them to the dispaly
179      do {
180
181        u8g.setFont(u8g_font_5x7);
182  // This can be adjusted to various fonts.  See:  https://github.com/olikraus/u8glib/wiki/fontsize
183
184        u8g.setPrintPos(0,7);       // Position of first line
185        u8g.print(OLED_string_1);
186
187        u8g.setFont(u8g_font_helvB14); // Little biger and bolder font as this is
188  the temperature and humidy
189        u8g.setPrintPos(0, 25);        // Position
190  of second line
191        u8g.print(OLED_string_2);
192
193         } while (u8g.nextPage()
194  );
195  }
196
197
198
199
200void monthStr(tmElements_t tm)
201{
202
203   int int_month;
204
205   
206   str_month = tm.Month;
207   int_month = str_month.toInt();
208
209   switch(int_month)
210
211   {
212   case 1:
213         str_month =("JAN");
214         break;
215   case
216  2:
217         str_month =("FEB");
218         break;
219   case 3:
220         str_month
221  =("MAR");
222         break;
223   case 4:
224         str_month =("APR");
225
226         break;
227   case 5:
228         str_month =("MAY");
229         break;
230
231   case 6:
232         str_month =("JUN");
233         break;
234   case 7:
235
236         str_month =("JUL");
237         break;
238   case 8:
239         str_month
240  =("AUG");
241         break;
242   case 9:
243         str_month =("SEP");
244
245         break;
246   case 10:
247         str_month =("OCT");
248         break;
249
250   case 11:
251         str_month =("NOV");
252         break;
253   case 12:
254
255         str_month =("DEC");
256         break;
257   default:
258         str_month
259  =("ERR");
260         break;
261      }
262      
263}
264
265
266
267void timeStr(tmElements_t
268  tm)
269{
270
271  // Add a leading zero when needed so all numbers are two characters
272
273   
274  String hours,seconds,minutes;
275
276  if(tm.Hour<10)
277  {
278    hours
279  = "0"+String(tm.Hour);
280  }
281  else
282  { 
283    hours = String(tm.Hour);
284  
285   }
286  
287  if(tm.Minute<10)
288  {
289    minutes = "0"+String(tm.Minute);
290
291  }
292  else
293  { 
294    minutes = String(tm.Minute); 
295   }
296
297  // We're
298  processing seconds "just in case", but not adding them to the small display 
299
300  
301  if(tm.Second<10)
302  {
303    seconds = "0"+String(tm.Second);
304  }
305
306  else
307  { 
308    seconds = String(tm.Second); 
309   }
310   
311  str_time
312  = hours + ":" + minutes;
313}
314  
315
316
317
318void setup() 
319  { 
320   //
321  Start Wire library for I2C
322   Wire.begin();  
323   clearOLED();  
324   dht.begin();
325
326   // initialize digital pin LED_BUILTIN as an output.
327   pinMode(LED_BUILTIN,
328  OUTPUT); 
329   Initialize();
330  } 
331
332
333
334
335void loop()
336  { 
337
338    int i, median_index;
339    
340    RTC.read(tm);  // Get the date and time
341
342    monthStr(tm);  // Convert the month from a number to Jan, Feb, Mar, etc
343
344    timeStr(tm);   // Convert the time to strings
345
346    h = dht.readHumidity();
347         // Get Humidity value
348    t = dht.readTemperature();      // Get Temperature
349  value
350
351    // Replace the oldest value with the newest just read by moving
352  every element in 
353    // the arrays up one and sticking this new value in the
354  bottom.
355    for (i = 0 ; i < buff_size - 1 ; i++)
356      {   
357        h_array[i]
358  = h_array[i + 1];
359        t_array[i] = t_array[i + 1];
360      }
361    h_array[buff_size-1]
362  = h;
363    t_array[buff_size-1] = t;
364
365    // Move them into the sort arrays
366
367    for (i = 0 ; i < buff_size ; i++)
368      {    
369        h_array_sort[i]
370  = h_array[i];
371        t_array_sort[i] = t_array[i];
372      }
373
374    //
375  Sort them. Use quick and dirty bubble sort because it's a small number of data points
376
377    bubble_sort(h_array_sort, buff_size);
378    bubble_sort(t_array_sort, buff_size);
379
380
381    // Use the median of the last "buff_zize" readings for the display
382    median_index
383  = buff_size / 2;
384    h = h_array_sort[median_index]; 
385    t = t_array_sort[median_index];
386
387    string_Temp  = String(t,1);     // Make temp a character string
388    string_Humid
389  = String(h,1);     // Make humid a character string
390    
391    //  Build first
392  OLED line
393    str_year = tmYearToCalendar(tm.Year);
394    str_day = tm.Day;
395
396    str_day = str_day + "-";
397    str_month = str_month + "-";
398    temporary_string
399  = "    " + str_day + str_month + str_year + " " + str_time;
400    strcpy(OLED_string_1,
401  temporary_string.c_str());      // Put date/time string in the first character array
402
403    
404    //  Build second OLED line
405    temporary_string = "";
406    temporary_string
407  = temporary_string + string_Temp + char(176) + "C   ";  // char(176) is the degree
408  symbol
409    temporary_string = temporary_string + string_Humid + " %";    
410
411    strcpy(OLED_string_2, temporary_string.c_str());      // Put temperature/humidity
412  string in the second character array
413    
414    
415    sendstringstoDisplay();
416             // Display the median temperature and humidity
417    delay(5000);
418                        // Updates every 5 seconds
419  
420  }

/*
 
  Use an Arduino Nano to display temp/humidy on 0.96 inch Yellow/Blue
  IIC OLED I2c 
  serial 128x64 Display
  
  Use an Adafruit DHT22 Temperature
  and Humidity Sensor (accuracy ±2%)

  These data might bounce around somewhat
  because the sensor can be a little noisy
  at times.  We use a simple median
  filter to smooth out the noise
  
  Arduino Nano <--> OLED = pin A4 to SDA
  and pin A5 to SLC 

  February 2020

  Paul M Dunphy, VE1DX
  
*/


//
  This library allows you to communicate with I2C devices, in this
// case the
  RTC and OLED display
#include <Wire.h> 

// For the DS3231 Real time Clock
  Module (AT24C32 Module)
#include <DS1307RTC.h>

// Include DHT Library
  from Adafruit

#include "DHT.h";
/* DHT22 pin-out:
   Pin 1 VCC 

   Pin 2 Data out
   Pin 3 Not connected
   Pin 4 Ground
*/

#include
  "U8glib.h"  // For the OLED - Obtain from: https://github.com/olikraus/u8glib

//
  Define Constants
 
#define dhtPin 7        // DHT-22 Output Pin connection
#define
  dhtType DHT22   // DHT Type is a DHT 22 (AM2302)

// Initialize OLED
U8GLIB_SSD1306_128X32
  u8g(U8G_I2C_OPT_NONE);

// Initialize DHT sensor
 
DHT dht(dhtPin, dhtType);
  

tmElements_t tm;  // For the RTC

#define buff_size 7  // Must be
  an odd number.  Should be greater than 5.  7 works well.

unsigned long a_second
  = 1000;
float h = 0.0;  //Stores humidity value
float t = 0.0;  //Stores temperature
  value
float h_array[buff_size] = {0.0};
float t_array[buff_size] = {0.0};
float
  h_array_sort[buff_size] = {0.0};
float t_array_sort[buff_size] = {0.0};
String
  string_Temp, string_Humid, temporary_string, tick_string;

 
char OLED_string_1[50];
  // Need a couple of character buffers to hold the two OLED lines
char OLED_string_2[50];


String
  str_day, str_month, str_year, str_time; // Lot of conversion to strings required
  because the
                                               // DSD Tech display
  doesn't like integers and floats


void clearOLED()
  {
    u8g.firstPage();
  
    do {
    } while( u8g.nextPage() );
  }


void Initialize()
{

  float startup_delay;
  int i;
  
  clearOLED();
  startup_delay =
  buff_size * (a_second * 5.0 / 1000.0);
  temporary_string  = String(startup_delay,0);

  temporary_string = " (" + temporary_string + " seconds)";

  tick_string
  = "Initializing "; 
  strcpy(OLED_string_1, tick_string.c_str());
  strcpy(OLED_string_2,
  temporary_string.c_str());
  
  // Take "buff_size" readings of each parameter,
  one every 5 seconds,
  // to get initial arrays of data.  Print "status" dots
  across display.
  for (i = 0 ; i < buff_size ; i++)
    {    
       tick_string
  = tick_string + ". ";
       strcpy(OLED_string_1, tick_string.c_str());

       sendstringstoDisplay();
       delay(a_second * 5);
       h_array[i]
  = dht.readHumidity();       // Get Humidity value
       t_array[i] = dht.readTemperature();
    // Get Temperature value
    }    
  }



void bubble_sort(float
  sort_array[], int n)
  {
  int i, j;
  float  temp;
 
  for (i =
  0 ; i < n - 1; i++)
    {
      for (j = 0 ; j < n - i - 1; j++)
        {

          if (sort_array[j] > sort_array[j+1])
            {
            //
  Swap values 
            temp            = sort_array[j];
            sort_array[j]
   = sort_array[j+1];
            sort_array[j+1] = temp;
            }

          }
      }
  }




void sendstringstoDisplay()

  {
    u8g.firstPage();  // Send them to the dispaly
      do {

        u8g.setFont(u8g_font_5x7);
  // This can be adjusted to various fonts.  See:  https://github.com/olikraus/u8glib/wiki/fontsize

        u8g.setPrintPos(0,7);       // Position of first line
        u8g.print(OLED_string_1);

        u8g.setFont(u8g_font_helvB14); // Little biger and bolder font as this is
  the temperature and humidy
        u8g.setPrintPos(0, 25);        // Position
  of second line
        u8g.print(OLED_string_2);

         } while (u8g.nextPage()
  );
  }




void monthStr(tmElements_t tm)
{

   int int_month;

   
   str_month = tm.Month;
   int_month = str_month.toInt();

   switch(int_month)

   {
   case 1:
         str_month =("JAN");
         break;
   case
  2:
         str_month =("FEB");
         break;
   case 3:
         str_month
  =("MAR");
         break;
   case 4:
         str_month =("APR");

         break;
   case 5:
         str_month =("MAY");
         break;

   case 6:
         str_month =("JUN");
         break;
   case 7:

         str_month =("JUL");
         break;
   case 8:
         str_month
  =("AUG");
         break;
   case 9:
         str_month =("SEP");

         break;
   case 10:
         str_month =("OCT");
         break;

   case 11:
         str_month =("NOV");
         break;
   case 12:

         str_month =("DEC");
         break;
   default:
         str_month
  =("ERR");
         break;
      }
      
}



void timeStr(tmElements_t
  tm)
{

  // Add a leading zero when needed so all numbers are two characters

   
  String hours,seconds,minutes;

  if(tm.Hour<10)
  {
    hours
  = "0"+String(tm.Hour);
  }
  else
  { 
    hours = String(tm.Hour);
  
   }
  
  if(tm.Minute<10)
  {
    minutes = "0"+String(tm.Minute);

  }
  else
  { 
    minutes = String(tm.Minute); 
   }

  // We're
  processing seconds "just in case", but not adding them to the small display 

  
  if(tm.Second<10)
  {
    seconds = "0"+String(tm.Second);
  }

  else
  { 
    seconds = String(tm.Second); 
   }
   
  str_time
  = hours + ":" + minutes;
}
  



void setup() 
  { 
   //
  Start Wire library for I2C
   Wire.begin();  
   clearOLED();  
   dht.begin();

   // initialize digital pin LED_BUILTIN as an output.
   pinMode(LED_BUILTIN,
  OUTPUT); 
   Initialize();
  } 




void loop()
  { 

    int i, median_index;
    
    RTC.read(tm);  // Get the date and time

    monthStr(tm);  // Convert the month from a number to Jan, Feb, Mar, etc

    timeStr(tm);   // Convert the time to strings

    h = dht.readHumidity();
         // Get Humidity value
    t = dht.readTemperature();      // Get Temperature
  value

    // Replace the oldest value with the newest just read by moving
  every element in 
    // the arrays up one and sticking this new value in the
  bottom.
    for (i = 0 ; i < buff_size - 1 ; i++)
      {   
        h_array[i]
  = h_array[i + 1];
        t_array[i] = t_array[i + 1];
      }
    h_array[buff_size-1]
  = h;
    t_array[buff_size-1] = t;

    // Move them into the sort arrays

    for (i = 0 ; i < buff_size ; i++)
      {    
        h_array_sort[i]
  = h_array[i];
        t_array_sort[i] = t_array[i];
      }

    //
  Sort them. Use quick and dirty bubble sort because it's a small number of data points

    bubble_sort(h_array_sort, buff_size);
    bubble_sort(t_array_sort, buff_size);


    // Use the median of the last "buff_zize" readings for the display
    median_index
  = buff_size / 2;
    h = h_array_sort[median_index]; 
    t = t_array_sort[median_index];

    string_Temp  = String(t,1);     // Make temp a character string
    string_Humid
  = String(h,1);     // Make humid a character string
    
    //  Build first
  OLED line
    str_year = tmYearToCalendar(tm.Year);
    str_day = tm.Day;

    str_day = str_day + "-";
    str_month = str_month + "-";
    temporary_string
  = "    " + str_day + str_month + str_year + " " + str_time;
    strcpy(OLED_string_1,
  temporary_string.c_str());      // Put date/time string in the first character array

    
    //  Build second OLED line
    temporary_string = "";
    temporary_string
  = temporary_string + string_Temp + char(176) + "C   ";  // char(176) is the degree
  symbol
    temporary_string = temporary_string + string_Humid + " %";    

    strcpy(OLED_string_2, temporary_string.c_str());      // Put temperature/humidity
  string in the second character array
    
    
    sendstringstoDisplay();
             // Display the median temperature and humidity
    delay(5000);
                        // Updates every 5 seconds
  
  }

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