Bicycle Speedometer with Reed Switch and Interrupts

1#include <LiquidCrystal.h>
2const int rs = 7, en = 2, d4 = 13, d5 = 12, d6 = 11, d7 = 10;
3LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
4
5#define CLOCK_FREQUENCY 16000000
6volatile unsigned int secs = 0;
7
8#define magnet 3 //magnetic switch
9int count = 0; //revolutions of the wheel
10double t = 0; //timestamp since start of program
11double distance = 0.0013048795; //distance traveled in miles in one revolution of the wheel if wheel diameter is 26.32 in
12double velocity = 0; //value updated every revolutions of wheel
13double lastTime = 0; //timestamp of last revoution
14double odometer = 0; //total distance traveled
15volatile bool state = false; //state of magnetic switch
16
17// custom characters
18uint8_t empty[8] = {0b00000,0b00000,0b00000,0b00000,0b00000,0b00000,0b00000,0b00000};
19uint8_t l[8] = {0b10000,0b10000,0b10000,0b10000,0b10000,0b10000,0b10000,0b10000};
20uint8_t ml[8] = {0b11000,0b11000,0b11000,0b11000,0b11000,0b11000,0b11000,0b11000};
21uint8_t center[8] = {0b11100,0b11100,0b11100,0b11100,0b11100,0b11100,0b11100,0b11100};
22uint8_t mr[8] = {0b11110,0b11110,0b11110,0b11110,0b11110,0b11110,0b11110,0b11110};
23uint8_t r[8] = {0b11111,0b11111,0b11111,0b11111,0b11111,0b11111,0b11111,0b11111};
24
25String custChars[6] = {"\x01","\x02","\x03","\x04","\x05","\x06"};
26
27// int i = 0;
28// int c = 0;
29int idleCount = 0; //seconds since last revolution
30int oneLoopCount = 0; //to only clear lcd once when in idle
31
32// ISR function 
33void updateSpeed(){
34  state = true; //true when magnetic switch is closed
35}
36
37// timer driven interrrupt to track idle time
38ISR(TIMER1_COMPA_vect) {
39 idleCount = idleCount + 1;
40}
41
42void setup() {
43  Serial.begin(9600);
44  // set up the LCD's number of columns and rows:
45  lcd.begin(16, 2);
46  
47  // inputpullup seems to be required for this sensor; need to drive current maybe?
48  pinMode(magnet, INPUT_PULLUP);
49  
50  // choose the interrupt sensing mode
51  attachInterrupt(digitalPinToInterrupt(magnet), updateSpeed, FALLING);
52  
53  //set frequency of the timer, timer driven interrupt every T = 1/freq
54  setupTimer(1.0);
55  
56  // create custom characters
57  lcd.createChar(1, empty);
58  lcd.createChar(2, l);
59  lcd.createChar(3, ml);
60  lcd.createChar(4, center);
61  lcd.createChar(5, mr);
62  lcd.createChar(6, r);
63}
64
65void loop() {
66  t = (millis() / 1000.0);
67  int h = floor(t/3600);
68  int m = floor(t/60) - (60*floor(t/3600));
69  int s = floor(t) - (60*floor(t/60));
70
71//  lcd.setCursor(0, 0);
72//  lcd.print(h);
73//  lcd.setCursor(1, 0);
74//  lcd.print(":");
75//  lcd.setCursor(3, 0);
76//  lcd.print(m);
77//  lcd.setCursor(4, 0);
78//  lcd.print(":");
79//  lcd.setCursor(5, 0);
80//  lcd.print(s);
81
82    lcd.setCursor(0,0);
83    lcd.print(m);
84    lcd.setCursor(2,0);
85    lcd.print("min");
86
87  if(idleCount >= 7){
88    velocity = 0.0;
89
90    // clear LCD once
91    if(oneLoopCount == 0){
92      lcd.clear();
93      oneLoopCount = 1;
94    }
95
96    // print velocity
97    lcd.setCursor(7, 0);
98    lcd.print(velocity);
99    lcd.setCursor(13, 0);
100    lcd.print("mph");
101
102    // print odometer
103    lcd.setCursor(0,1);
104    lcd.print(odometer);
105    lcd.setCursor(5, 1);
106    lcd.print("mi");
107
108    // print velocity graphic
109    int bars = floor(velocity);
110    int sects = bars/5;
111    lcd.setCursor(8+sects,1);
112    bars = bars - 5*sects;
113    lcd.print(custChars[bars]);
114    for(int u = 0;u<sects;u++){
115      lcd.setCursor(8+u,1);
116      lcd.print(custChars[5]);
117    }
118  }
119  
120  if(state){
121    // update revolution count and velocity calculation
122    count++;
123    velocity = ((distance * 3600)/((t - lastTime)));
124
125    // zero velocities over 50 mph as assumed double counts, can be adjusted if you fast
126    if((t - lastTime) <= 0.09396){
127      velocity = 0.0;
128    }
129
130    // clear LCD each iteration for graphic
131    lcd.clear();
132
133    // print velocity
134    lcd.setCursor(7, 0);
135    lcd.print(velocity);
136    lcd.setCursor(13, 0);
137    lcd.print("mph");
138    
139    // i += 1;
140    // if(i > 2){
141    //   c += 1;
142    //   if(c > 4){
143    //     c = 0;
144    //   }
145    //   //RGB_color_picker(c);
146    //   i = 0;
147    // }
148    
149    // update variables 
150    lastTime = t;
151    state = false;
152    idleCount = 0;
153    oneLoopCount = 0;
154  }
155
156  // recalculate odometer
157  odometer = count * distance;
158
159  // print odometer
160  lcd.setCursor(0,1);
161  lcd.print(odometer);
162  lcd.setCursor(5, 1);
163  lcd.print("mi");
164
165  // print velocity graphic
166  int bars = floor(velocity);
167  int sects = bars/5;
168  lcd.setCursor(8+sects,1);
169  bars = bars - 5*sects;
170  lcd.print(custChars[bars]);
171  for(int u = 0;u<sects;u++){
172    lcd.setCursor(8+u,1);
173    lcd.print(custChars[5]);
174  }
175}
176
177void setupTimer(float freq){
178// set up Timer
179 noInterrupts(); // stop interrupts
180
181 //set Timer1 interrupt at 1 Hz = 1 time per second
182 TCCR1A = 0; // initialize TCCR1A register
183 TCCR1B = 0; // initialize TCCR1B register
184 TCNT1 = 0; // initialize counter value to 0
185 // turn on CTC mode
186 TCCR1B |= (1 << WGM12);
187 // set CS10 and CS12 bits for 1024 prescaler
188 TCCR1B |= (1 << CS12) | (1 << CS10);
189 // set compare match register for 1hz increments
190 OCR1A = CLOCK_FREQUENCY/freq/1024 - 1; 
191 // enable timer compare match A interrupt
192 TIMSK1 |= (1 << OCIE1A);
193
194 interrupts(); // allow interrupts
195}