Thread: Flex-fuel sensor output

/*******************************************************

This program will sample a 50-150hz signal depending on ethanol 

content, and output a 0-5V signal via PWM.

The LCD will display ethanol content, hz input, mv output, fuel temp



Connect PWM output to NEMU Breakoutboard on ADC0-3, and tune

the "FLEX FUEL SETUP" tab accordingly. NOTE: Lowpass filter to

be used on output.



Input pin 8 (PB0) ICP1 on Atmega328

Output pin 3 PWM



If LCD Keypad shield is used, solder jumper from Pin 8 - Pin 2,

and snip leg from pin 8 http://i.imgur.com/KdlLmye.png

********************************************************/



// include the library code:

#include  //LCD plugin



// initialize the library with the numbers of the interface pins 

LiquidCrystal lcd(2, 9, 4, 5, 6, 7); //LCD Keypad Shield



int inpPin = 8;     //define input pin to 8

int outPin = 3;    //define PWM output, possible pins with LCD are 3, 10 and 11 (UNO)



//Define global variables

volatile uint16_t revTick;    //Ticks per revolution

uint16_t pwm_output  = 0;     //integer for storing PWM value (0-255 value)

int HZ = 0;                   //unsigned 16bit integer for storing HZ input

int ethanol = 0;              //Store ethanol percentage here



int duty;           //Duty cycle (0.0-100.0)

float period;       //Store period time here (eg.0.0025 s)

float temperature = 0;  //Store fuel temperature here

int fahr = 0;

int cels = 0;

static long highTime = 0;

static long lowTime = 0;

static long tempPulse;



void setupTimer()	 // setup timer1

{           

	TCCR1A = 0;      // normal mode

	TCCR1B = 132;    // (10000100) Falling edge trigger, Timer = CPU Clock/256, noise cancellation on

	TCCR1C = 0;      // normal mode

	TIMSK1 = 33;     // (00100001) Input capture and overflow interupts enabled

	TCNT1 = 0;       // start from 0

}



ISR(TIMER1_CAPT_vect)    // PULSE DETECTED!  (interrupt automatically triggered, not called by main program)

{

	revTick = ICR1;      // save duration of last revolution

	TCNT1 = 0;	     // restart timer for next revolution

}



ISR(TIMER1_OVF_vect)    // counter overflow/timeout

{ revTick = 0; }        // Ticks per second = 0





void setup()

{

  pinMode(inpPin,INPUT);

  setPwmFrequency(outPin,1); //Modify frequency on PWM output

 setupTimer();

   // set up the LCD's number of columns and rows:

  lcd.begin(16, 2);

  // Initial screen formatting

  lcd.setCursor(0, 0);

  lcd.print("Ethanol:    %");

  lcd.setCursor(0, 1);

  lcd.print("     Hz       C");

}

 

void loop()

{

  getfueltemp(inpPin); //read fuel temp from input duty cycle

  

  if (revTick > 0) // Avoid dividing by zero, sample in the HZ

		{HZ = 62200 / revTick;}     // 3456000ticks per minute, 57600 per second 

		else                        // 62200 per seconmd seems to be more accurate? 

		{HZ = 0;}                   //needs real sensor test to determine correct tickrate



  //calculate ethanol percentage

		if (HZ > 50) // Avoid dividing by zero

		{ethanol = HZ-50;}

		else

		{ethanol = 0;}



if (ethanol > 99) // Avoid overflow in PWM

{ethanol = 99;}



  //Screen calculations

  pwm_output = 255 * (ethanol*0.01); //calculate output PWM for NEMU

  

  lcd.setCursor(10, 0);

  lcd.print(ethanol);

  

  lcd.setCursor(2, 1);

  lcd.print(HZ);

  

  lcd.setCursor(8, 1); 

  lcd.print(temperature); //Use this for celsius



  //PWM output

  analogWrite(outPin, pwm_output); //write the PWM value to output pin



  delay(100);  //make screen more easily readable by not updating it too often

  

}



void getfueltemp(int inpPin){ //read fuel temp from input duty cycle

highTime = 0;

lowTime = 0;



tempPulse = pulseIn(inpPin,HIGH);

  if(tempPulse>highTime){

  highTime = tempPulse;

  }



tempPulse = pulseIn(inpPin,LOW);

  if(tempPulse>lowTime){

  lowTime = tempPulse;

  }



duty = ((100*(highTime/(double (lowTime+highTime))))); //Calculate duty cycle (integer extra decimal)

float T = (float(1.0/float(HZ)));               //Calculate total period time

float period = float(100-duty)*T;               //Calculate the active period time (100-duty)*T

float temp2 = float(10) * float(period);        //Convert ms to whole number

temperature = ((40.25 * temp2)-81.25); // Calculate temperature for display (1ms = -40, 5ms = 80)

int cels = int(temperature);

cels = cels*0.1;

float fahrtemp = ((temperature*1.8)+32);

fahr = fahrtemp*0.1;



}



void setPwmFrequency(int pin, int divisor) {

  byte mode;

  if(pin == 5 || pin == 6 || pin == 9 || pin == 10) {

    switch(divisor) {

      case 1: mode = 0x01; break;

      case 8: mode = 0x02; break;

      case 64: mode = 0x03; break;

      case 256: mode = 0x04; break;

      case 1024: mode = 0x05; break;

      default: return;

    }

    if(pin == 5 || pin == 6) {

      TCCR0B = TCCR0B & 0b11111000 | mode;

    } else {

      TCCR1B = TCCR1B & 0b11111000 | mode;

    }

  } else if(pin == 3 || pin == 11) {

    switch(divisor) {

      case 1: mode = 0x01; break;

      case 8: mode = 0x02; break;

      case 32: mode = 0x03; break;

      case 64: mode = 0x04; break;

      case 128: mode = 0x05; break;

      case 256: mode = 0x06; break;

      case 1024: mode = 0x7; break;

      default: return;

    }

    TCCR2B = TCCR2B & 0b11111000 | mode;

  }

}