Simplest 24h UNO Digital Clock Ever!

1#include "LiquidCrystal.h"
2
3// This defines the LCD wiring to  the DIGITALpins
4const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
5LiquidCrystal  lcd(rs, en, d4, d5, d6, d7);
6
7// Digital LCD Constrast setting
8int cs=9;//  pin 9 for contrast PWM
9const int contrast = 100;// default contrast
10
11//  initial Time display is 24:59:45 PM
12int h=24;
13int m=59;
14int s=45;
15int  flag=1; //PM
16
17// Time Set Buttons
18int button1;
19int button2;
20
21//  Pins definition for Time Set Buttons
22int hs=0;// pin 0 for Hours Setting
23int  ms=1;// pin 1 for Minutes/Preset Seconds(0) Setting
24
25// Backlight Time Out  
26const int Time_light=150;
27int bl_TO=Time_light;// Backlight Time-Out
28int  bl=10; // Backlight pin
29const int backlight=120; // no more then 7mA !!!
30
31//  For accurate Time reading, use Arduino Real Time Clock and not just delay()
32static  uint32_t last_time, now = 0; // RTC
33
34
35void setup()
36{
37  lcd.begin(16,2);
38  pinMode(hs,INPUT_PULLUP);// avoid external Pullup resistors for Button 1
39  pinMode(ms,INPUT_PULLUP);//  and Button 2
40  analogWrite(cs,contrast);// Adjust Contrast VO
41  analogWrite(bl,backlight);//  Turn on Backlight
42  now=millis(); // read RTC initial value 
43  
44   
45}
46
47
48void  loop()
49{ 
50  lcd.begin(16,2);// every second
51// Update LCD Display
52//  Print TIME in Hour, Min, Sec 
53 lcd.setCursor(0,0);
54 lcd.print("Time ");
55  if(h<10)lcd.print("0");// always 2 digits
56 lcd.print(h);
57 lcd.print(":");
58  if(m<10)lcd.print("0");
59 lcd.print(m);
60 lcd.print(":");
61 if(s<10)lcd.print("0");
62  lcd.print(s);
63
64
65
66 
67 lcd.setCursor(0,1);// for Line 2
68 lcd.print("ClockDePrecision");
69
70
71//  improved replacement of delay(1000) 
72// Much better accuracy, no more dependant  of loop execution time
73
74for ( int i=0 ;i<5 ;i++)// make 5 time 200ms loop,  for faster Button response
75{
76
77  while ((now-last_time)<200) //delay200ms
78  { 
79    now=millis();
80  }
81 // inner 200ms loop
82 last_time=now; // prepare  for next loop 
83
84 // read Setting Buttons
85 button1=digitalRead(hs);// Read  Buttons
86 button2=digitalRead(ms);
87
88 //Backlight time out 
89 bl_TO--;
90  if(bl_TO==0)
91 {
92  analogWrite(bl,0);// Backlight OFF
93  bl_TO++;
94 }
95  
96 // Hit any to activate Backlight 
97 if(  ((button1==0)|(button2==0)) & (bl_TO==1)  )
98 {
99  bl_TO=Time_light;
100  analogWrite(bl,backlight);
101  // wait until  Button released
102  while ((button1==0)|(button2==0))
103  {
104   button1=digitalRead(hs);//  Read Buttons
105   button2=digitalRead(ms);
106  }
107 }
108 else
109 // Process  Button 1 or Button 2 when hit while Backlight on 
110 {
111  if(button1==0){
112   h=h+1;
113   bl_TO=Time_light;
114   analogWrite(bl,backlight);
115  }
116
117  if(button2==0){
118  s=0;
119  m=m+1;
120  bl_TO=Time_light;
121  analogWrite(bl,backlight);
122  }
123
124/* ---- manage seconds, minutes, hours overflow ----*/
125 if(s==60){
126  s=0;
127  m=m+1;
128 }
129 if(m==60)
130 {
131  m=0;
132  h=h+1;
133 }
134 if(h==24)
135  {
136  h=0;
137  flag=flag;
138  
139 }
140
141
142 if((button1==0)|(button2==0))//  Update display if time set button pressed
143 {
144  // Update LCD Display
145  //  Print TIME in Hour, Min, Sec 
146  lcd.setCursor(0,0);
147  lcd.print("Time ");
148  if(h<10)lcd.print("0");// always 2 digits
149  lcd.print(h);
150  lcd.print(":");
151  if(m<10)lcd.print("0");
152  lcd.print(m);
153  lcd.print(":");
154  if(s<10)lcd.print("0");
155  lcd.print(s);
156
157  
158  lcd.setCursor(0,1);// for Line 2
159  lcd.print("Precision  clock");
160 }
161
162
163 } // end if else
164}// end for
165
166
167
168// outer  1000ms loop
169
170 s=s+1; //increment sec. counting
171    
172    
173// ----  manage seconds, minutes, hours am/pm overflow ----
174 if(s==60){
175  s=0;
176  m=m+1;
177 }
178 if(m==60)
179 {
180  m=0;
181  h=h+1;
182 }
183 if(h==24)
184  {
185  h=0;
186  flag=flag;
187 } 
188 
189
190 
191// Loop end
192}