Speedometer.c

/*
* Speeedometer
* Author: Jeff Hansen
* Description:
    Simulate a speedometer (kilometers per hour),
    1 second is 1 minute (didn't want to wait 1 real minute to see changes..)
    
    Have fun.
    
* License: MIT - do what you want, but I did the original work - don't forget.
*/

#include <utils.h>

// Address in the EEPROM where the first of the 2 bytes of data reside.
#define KM_ADDR 0x10


// LCD module connections
sbit LCD_RS at RB4_bit;
sbit LCD_EN at RB5_bit;
sbit LCD_D4 at RB0_bit;
sbit LCD_D5 at RB1_bit;
sbit LCD_D6 at RB2_bit;
sbit LCD_D7 at RB3_bit;

sbit LCD_RS_Direction at TRISB4_bit;
sbit LCD_EN_Direction at TRISB5_bit;
sbit LCD_D4_Direction at TRISB0_bit;
sbit LCD_D5_Direction at TRISB1_bit;
sbit LCD_D6_Direction at TRISB2_bit;
sbit LCD_D7_Direction at TRISB3_bit;
// End LCD module connections

// Globals
unsigned int adcInput;
unsigned int timerCounter;
bit shouldUpdateSpeedometer;
bit shouldUpdateTotal;

/*
* Umion for managing ints in EEPROM
*/
union eeprom_int {
  unsigned int value;
  char memory[2];
};

/*
* Called by hardware Interrupt when the interrupt was generated by a timer.
*/
void timerInterrupt() {
  if(timerCounter % 50 == 0) {
    // Half a seccond has ellapsed
    shouldUpdateSpeedometer = 1;
  }
  
  if(timerCounter % 100 == 0) {
    // One second has ellapsed
    shouldUpdateTotal = 1;
    
    // Reset the timer counter - not required but why not.
    timerCounter = 0;
  }

  timerCounter++;
}

/*
* Hardware interrupt.
*/
void interrupt(){
  if (TMR0IF_bit){
    TMR0IF_bit         = 0;
    TMR0         = 100;
    
    timerInterrupt();
  }
}

/*
 Initializes all globals and sets default bits in registers.
*/
void initialize(){
  C1ON_bit         = 0;     // Disable comparators
  C2ON_bit         = 0;
  ANSEL            = 0x04;  // Configure AN2 pin as analog
  ANSELH           = 0;     // Configure other AN pins as digital I/O

  // Initialize timer 0 to interrupt every 10ms
  OPTION_REG       = 0x86;
  TMR0             = 100;
  INTCON           = 0xA0;
  
  // Init LCD
  Lcd_Init();
  Lcd_Cmd(_LCD_CLEAR);
  
  // Initialize globals
  timerCounter     = 0;
}

/*
* Entry point
*/
void main() {
  // Variables
  char speedBuf[5] = {0,0,0,0,0};
  char totalBuf[] = {0,0,0,0,0,0,0,0,0,0};
  char empty[] = "                ";
  union eeprom_int totalKm;
  int kph = 1;

  // Initialization
  initialize();
  
  // 0x10 = first byte of the actual int value
  // 0x11 = second byte of the actual int value
  totalKm.memory[0] = EEPROM_Read(KM_ADDR);
  totalKm.memory[1] = EEPROM_Read(KM_ADDR+1);

  // 0xFF is 8 bit, an uint is 2 byte = 16 bit, so we need 0xFFFF
  if(totalKm.value == 0xFFFF) {
    totalKm.value = 0;
  }
  
  do {
    // Reads the value of the RA2 Analog knob.
    adcInput = ADC_Read(2);

    
    if(shouldUpdateSpeedometer == 1) {
      shouldUpdateSpeedometer = 0;
      // Update speedometer LCD here
      speed(speedBuf, adcInput, &kph);
      Lcd_Out(1,1,empty);
      Lcd_Out(1,1,"km/t: ");
      Lcd_Out(1,7,speedBuf);
    }
    
    if(shouldUpdateTotal) {
      shouldUpdateTotal = 0;
      // Update LCD and save total here
      total(totalBuf, &totalKm.value, kph);
      
      EEPROM_Write(KM_ADDR, totalKm.memory[0]);
      EEPROM_Write(KM_ADDR+1, totalKm.memory[1]);
      Lcd_Out(2,1,empty);
      Lcd_Out(2,1, "Total: ");
      Lcd_Out(2,8, totalBuf);
    }
    
  }while(1);
}