Automotive speedometer for a camper

1/* 
2  "Speedometer for Diesel-Doris"
3  
4  Converts an aftermarket  mechanical speedometer signal to digital.
5  The speedometer converter output  is a frequency signal (1 pulse cycle/revolution).
6  The mechanical speedometer  output is ~1,307 m/revolution.
7  
8  Emil Backram
9  20 Dec 2020 - Project  start  (Uno Rev.3)
10  26 Dec 2020 - Succsessful lab test of basic algorithm -  serial printer
11  27 Dec 2020 - Succsessful lab test of basic algorithm - LCD
12  29 Dec 2020 - Semi-succsessful lab test of variable contrast and back-light: 
13                * Fixed setpoint back-light levels - OK
14                * Variable  back-light level - unstable 
15                * All contrast levels inbetween  ON and OFF - flickery (Note: No RC-filter!)
16  07 Jan 2021 - Succsessful lab test  of 
17                * new basic algorithm:
18                  + Added timer  interrupt
19                  + Count number of pulses every 250ms
20                  +  Calc speed using the sum of the last 4 puls counts
21                * variable  contrast and back-light: 
22                  + Smoth back-light level transition
23                  + Fixed the contrast flickering bug (digitalWrite --> analogWrite)
24                  + Added RC-filter to contrast output (HW)
25                *  new trip and odometer meter algoritm:
26                  + Store odometer data  in eeprom
27                  + Calculate trip data using the diff of odometer  data at startup and current odometer data
28  08 Jan 2021 - Rearranged #define  constants in 2 groups, 'configurable' and 'non-configurable' 
29  12 Jan 2021 -  Fixed EEPROM read bug when > 2 bytes - cast back to 'unsigned long' 
30  13 Jan  2021 - Updated comments and clarifications
31              - Splited read/write  from/to memory subroutine into separate read respective write subroutines
32  15  Jan 2021 - Changed display delay timer from calculating "next time" using millis()  to using a bool variable set in timer1 interrupt
33  17 Jan 2021 - Minor updates:
34                * Notes
35                * Names
36                * LCD visual  appearance
37                * Removed unused defines
38                * Made  eeprom read/write odometer data subroutines more generic --> unsigned long read/write  subroutines
39                * Moved some processing from timer1 interrupt to  main loop
40  22 Jan 2021 - Minor updates:
41                * Activate on chip  pullup for SPEED_PIN to match the hardware design
42                * Use pin 9  instead of 11 for the LCD, in order to free the last usable PWM capable pin 
43                  + Pin 3 and 11 use timer2 for PWM control 
44                  +  Pin 9 and 10 won't be used for PWM since timer1 is used for timer interrupt
45  25 Jan 2021 - Added servo control for "analog" speedometer
46  26 Jan 2021  - Added RPM handling
47                * Display RPM on the LCD
48                *  "Shiftlight", LCD light blinks two times when RPM is too high or low
49  27 Jan  2021 - Minor optimizations to minimize execution time and program memory space
50              - Fixed minor bug for "Shiftlight"
51  02 Feb 2021 - Updated shiftlight  enable functionality (only enabled when vehicle speed is within a certain interval)
52  18 Apr 2021 - Updated speed pulse sensor data. Test result: Mechanical speedometer  wire output is 0,765 m/revolution
53  20 Apr 2021 - Removed engine speed, and its  related functionalities (for now, due to mechanical difficulties)
54              -  Fixed brain somersault: 0,765 = revolutions/m --> ~1,307 m/revolution
55              -  Changed interrupt trigger from RISING (1 pulse/revolution) to CHANGE (2 pulses/revolution)  to increase resolution
56                * ~1,307 m/revolution --> ~0,654 m/pulse
57  03 May 2021 - Fixed light intensity bug (missing analog write)
58              -  Added floating average for vehicle speed
59  18 May 2021 - Fixed floating average  for vehicle speed bug
60*/
61
62/* Libraries */
63#include <EEPROM.h>
64#include  <LiquidCrystal.h>
65
66/* Pin definitions */
67LiquidCrystal lcd(4, 7, 8, 9,  12, 13);  //Pins chosen to avoid IRQ inputs and PWM outputs (Uno)
68#define SPEED_PIN         2             //Dig pin 2 = IRQ 0 (Uno)
69#define LCD_CONTRAST_PIN  5             //PWM pin 5 using Timer0 (Uno)
70#define LCD_LIGHT_PIN     6             //PWM  pin 6 using Timer0 (Uno)
71#define SERVO_PIN         11            //PWM pin 11  using Timer2 (Uno)
72#define LIGHT_SENS_PIN    A0            //Analog pin 0
73
74/*  Non-configurable system-specific constants */
75#define UPDATE_FREQUENCY  4       //Hz
76#define  OCR1A_VAL         62499   //Corresponds to UPDATE_FREQUENCY
77#define BYTE_SHIFT        8       //(bits)
78#define ODO_ADDR          0       //Odometer data address  in eeprom
79#define LCD_ROWS          2       //Number of rows in the LCD display
80#define  LCD_COLUMNS       16      //Number of columns in the LCD display
81#define LCD_UPPER         0       //(row)
82#define LCD_LOWER         1       //(row)
83#define  LCD_INIT_COLUMN   0       //(column)
84#define LCD_HALF_COLUMN   8       //(column)
85#define  OCR2A_MIN         7       //Corresponds to 180 degrees @ ~61Hz (Attention!!! This  works for my servo, it might damage yours! I found the limits through carefull trial  and error!)
86#define OCR2A_MAX         34      //Corresponds to 0 degrees @ ~61Hz  (Attention!!! This works for my servo, it might damage yours! I found the limits  through carefull trial and error!)
87
88/* Configurable vehicle-specific constants  */
89#define M_PER_PULSE           0.654f  //(m/pulse) Using CHANGE instead of  RISING for the interrupt will double the pulses per revolution
90#define SPEED_MIN             5       //(km/h)
91#define KPH_PER_SERVO_STEP    5       //(km/h)/step
92#define  LIGHT_SENS_LIMIT      300     //0-1023
93#define LCD_LIGHT_MAX         255     //LCD_LIGHT_MIN-255
94#define  LCD_LIGHT_MIN         10      //0-LCD_LIGHT_MAX
95#define LCD_CONTRAST          25      //0-255
96#define STARTUP_SCREEN_DELAY  2500    //(ms)
97
98/* Macros */
99#define  MIN_CONSTRAINT(X, MIN) ((X > MIN) ? X : MIN)
100#define MAX_CONSTRAINT(X, MAX) ((X  < MAX) ? X : MAX)
101#define VAL_CONSTRAINT(X, MIN, MAX) MAX_CONSTRAINT(MIN_CONSTRAINT(X,  MIN), MAX)
102
103#define DISTANCE_CALC(X) ((X * M_PER_PULSE) / 1000.f) //Input  (float)pulses, returns (km)
104#define SPEED_CALC(X)    (X * M_PER_PULSE * 3.6f)     //Input (float)pulses/s, returns (km/h)
105
106#define KPH_TO_SPEEDO_SERVO(KPH)  VAL_CONSTRAINT((OCR2A_MAX - (KPH / KPH_PER_SERVO_STEP)), OCR2A_MIN, OCR2A_MAX) //Input  km/h, returns PWM setpoint (OCR2A_MIN - OCR2A_MAX)
107
108/* Global variables */
109bool  volatile timer1_interrupt                              = false;
110byte volatile  orc2a_val                                     = OCR2A_MIN;
111byte volatile irq_array_cntr                                = 0;
112unsigned int volatile speed_irq_cntr                        =  0;
113unsigned int volatile speed_pulses_array[UPDATE_FREQUENCY]  = {0};
114
115/*  Subroutines */
116void display_vehicle_data(byte, unsigned long, unsigned long);
117unsigned  long eeprom_read_u_long(unsigned int);
118void eeprom_write_u_long(unsigned int,  unsigned long);
119
120/* Setup */
121void setup()
122{
123  /* Pins */
124  pinMode(SPEED_PIN,  INPUT_PULLUP);   //Activate pullup resistor for speed interrupt pin
125  pinMode(LIGHT_SENS_PIN,  INPUT); 
126  pinMode(LCD_LIGHT_PIN, OUTPUT); 
127  pinMode(LCD_CONTRAST_PIN, OUTPUT);  
128  pinMode(SERVO_PIN, OUTPUT);         //Output correspond to orc2a_val (no analogWrite()  in code)
129
130  /* Interrupts */
131  attachInterrupt(digitalPinToInterrupt(SPEED_PIN),  speed_isr, CHANGE); //Using CHANGE instead of RISING for the interrupt will double  the pulses per revolution
132  
133  cli();  //Clear global Interrupts
134  
135  /* Timer1 */
136  TCCR1A  = 0;                          //Clear register, CTC  mode
137  TCCR1B  = 0;                          //Clear register
138  TCNT1   =  0;                          //Clear register
139  OCR1A   = OCR1A_VAL;                  //Corresponds  to UPDATE_FREQUENCY
140  TCCR1B |= (1 << WGM12);               //CTC mode
141  TCCR1B  |= (1 << CS11) | (1 << CS10);  //64 prescaler, corresponds to UPDATE_FREQUENCY
142  TIMSK1 |= (1 << OCIE1A);              //Output Compare A Match Interrupt Enable
143
144  /* Timer2 (analog speed) */
145  TCCR2A  = 0;                                        //Clear  register
146  TCCR2B  = 0;                                        //Clear register
147  TCNT2   = 0;                                        //Clear register
148  OCR2A   = OCR2A_MIN;                                //Initial setpoint at startup (OCR2A_MIN  --> 'max' km/h)
149  TCCR2A |= (1 << COM2A1);                            //Compare  Output Mode (non-inverting mode)
150  TCCR2A |= (1 << WGM21) | (1 << WGM20);              //Fast  PWM Mode
151  TCCR2B |= (1 << CS22) | (1 << CS21) | (1 << CS20);  //1024 prescaler
152  TIMSK2 |= (1 << TOIE2);                             //Overflow Interrupt Enable
153  
154  sei();  //Set global interrupts
155  
156  /* LCD */
157  analogWrite(LCD_CONTRAST_PIN,  LCD_CONTRAST); 
158  lcd.begin(LCD_COLUMNS, LCD_ROWS);
159  lcd.setCursor(LCD_INIT_COLUMN,  LCD_UPPER);
160  lcd.print("<<<< Diesel >>>>");
161  lcd.setCursor(LCD_INIT_COLUMN,  LCD_LOWER);
162  lcd.print("<<<< Doris  >>>>");
163  analogWrite(LCD_LIGHT_PIN,  LCD_LIGHT_MAX);
164  delay(STARTUP_SCREEN_DELAY);
165  lcd.clear();
166  
167  /*  Analog speed (OCR2A_MAX --> 0 km/h) */
168  orc2a_val = OCR2A_MAX;  
169}
170
171/*  Main */
172void loop()
173{ 
174  static bool run_once = false;
175  static unsigned  long accumulated_speed_pulses = 0;
176  static const unsigned long init_odometer  = eeprom_read_u_long(ODO_ADDR);  //Fetch latest odometer data at startup
177
178  /* Calculate total distance (km) */
179  unsigned long current_odometer = (unsigned  long)DISTANCE_CALC((float)accumulated_speed_pulses) + eeprom_read_u_long(ODO_ADDR);
180
181  /* Calculate speed (km/h) and store odometer data */
182  unsigned long speed_pulses_per_s  = 0;
183  for(byte array_cntr = 0; array_cntr < UPDATE_FREQUENCY; array_cntr++)
184  {
185    speed_pulses_per_s += speed_pulses_array[array_cntr];
186  }
187  
188  float speed_kph = SPEED_CALC((float)speed_pulses_per_s);
189  if(speed_kph < SPEED_MIN)
190  {
191    speed_kph = 0.f;
192    accumulated_speed_pulses = 0;
193    if(run_once)  //Store odometer data in eeprom (only once when vehicle no longer is in motion)
194    {
195      eeprom_write_u_long(ODO_ADDR, current_odometer);
196      run_once  = false;
197    }
198  }
199  else
200  {
201    run_once = true;
202  }
203
204  /* Run when enabled by timer1 interrupt (Corresponds to UPDATE_FREQUENCY) */
205  if(timer1_interrupt)
206  {
207    static float vehicle_speed_array[UPDATE_FREQUENCY]  = {0.f};
208    timer1_interrupt = false; 
209    accumulated_speed_pulses += speed_pulses_array[irq_array_cntr];  //Accumulate latest odometer data
210    
211    irq_array_cntr++;
212    if(irq_array_cntr  >= UPDATE_FREQUENCY)
213    {
214      irq_array_cntr = 0;
215    }
216
217    /*  Vehicle speed average */
218    vehicle_speed_array[irq_array_cntr] = speed_kph;
219    float avg_speed_kph = 0;
220    for(byte array_cntr = 0; array_cntr < UPDATE_FREQUENCY;  array_cntr++)
221    {
222      avg_speed_kph += vehicle_speed_array[array_cntr];
223    }
224    avg_speed_kph = avg_speed_kph/(float)UPDATE_FREQUENCY;
225    
226    /* Display vehicle data (and calculate distance since startup (km)) */
227    display_vehicle_data((byte)avg_speed_kph,  (current_odometer - init_odometer), current_odometer);
228  }
229}
230
231/* Display  vehicle data */
232void display_vehicle_data(byte vehicle_speed, unsigned long vehicle_trip,  unsigned long vehicle_odometer)
233{
234  static byte lcd_light_intensity = 0xff;
235
236  /* LCD light intensity setpoint */
237  byte lcd_light_intensity_setpoint;
238  if(analogRead(LIGHT_SENS_PIN) > LIGHT_SENS_LIMIT)
239  {
240    lcd_light_intensity_setpoint  = LCD_LIGHT_MAX;
241  }
242  else
243  {
244    lcd_light_intensity_setpoint = LCD_LIGHT_MIN;
245  }
246
247  if(lcd_light_intensity < lcd_light_intensity_setpoint)
248  {
249    lcd_light_intensity++;
250  }
251  else if(lcd_light_intensity > lcd_light_intensity_setpoint)
252  {
253    lcd_light_intensity--;
254  }
255  analogWrite(LCD_LIGHT_PIN, lcd_light_intensity);
256
257  /* Analog speed */
258  orc2a_val = KPH_TO_SPEEDO_SERVO(vehicle_speed);
259
260  /* LCD vehicle data */
261  //No lcd.clear() to avoid display flickering. Lingering  artifacts are avoided anyway in the current design
262  lcd.setCursor(LCD_INIT_COLUMN,  LCD_UPPER);
263  lcd.print(vehicle_speed);
264  lcd.print("km/h  "); //'Blank  space' at the end to clear lingering artifacts when speed is decreasing
265  lcd.setCursor(LCD_INIT_COLUMN,  LCD_LOWER);
266  lcd.print(vehicle_trip);
267  lcd.print("km");
268  lcd.setCursor(LCD_HALF_COLUMN,  LCD_LOWER);
269  lcd.print(vehicle_odometer);
270  lcd.print("km");
271}
272
273/*  Read unsigned long data from eeprom */
274unsigned long eeprom_read_u_long(unsigned  int addr)
275{
276  unsigned long read_value = 0;
277  for(byte byte_cntr = 0; byte_cntr  < sizeof(read_value); byte_cntr++)
278  {
279    read_value |= (unsigned long)EEPROM.read(addr  + byte_cntr) << (BYTE_SHIFT * byte_cntr);
280  }
281  return read_value;
282}
283
284/*  Write unsigned long data to eeprom */
285void eeprom_write_u_long(unsigned int addr,  unsigned long write_value)
286{
287  for(byte byte_cntr = 0; byte_cntr < sizeof(write_value);  byte_cntr++)
288  {
289    EEPROM.update((addr + byte_cntr), (byte)(write_value  >> (BYTE_SHIFT * byte_cntr)));
290  }
291}
292
293/* Speed sensor ISR */
294void  speed_isr(void)
295{
296  speed_irq_cntr++;
297}
298
299/* Timer1 ISR */
300ISR(TIMER1_COMPA_vect)
301{
302  speed_pulses_array[irq_array_cntr] = speed_irq_cntr;
303  speed_irq_cntr = 0;
304  timer1_interrupt = true;
305}
306
307/* Timer2 ISR */
308ISR(TIMER2_OVF_vect)
309{
310  OCR2A = orc2a_val;
311}
312