AVR Freaks

/*****************************************************
This program was produced by the
CodeWizardAVR V2.04.8a Standard
Automatic Program Generator
© Copyright 1998-2010 Pavel Haiduc, HP InfoTech s.r.l.
http://www.hpinfotech.com

Project : Sequencer
Version : 
Date    : 1/25/2011
Author  : Mark
Company : 
Comments: 


Chip type               : ATtiny45
AVR Core Clock frequency: 1.000000 MHz
Memory model            : Tiny
External RAM size       : 0
Data Stack size         : 64
*****************************************************/

#include 

#include 

unsigned int Myadcvalue = 0;
unsigned int temp=0;
unsigned char adc_data;
unsigned int secondtimer=0;
unsigned int maxvalue=0;


// Timer1 output compare A interrupt service routine
interrupt [TIM1_COMPA] void timer1_compa_isr(void)
{
// Place your code here
 secondtimer++;
}

#define ADC_VREF_TYPE 0xA0  // I Changed from $B0 to $A0 for 1.1 Ref

// ADC interrupt service routine
interrupt [ADC_INT] void adc_isr(void)
{

// Read the 8 most significant bits
// of the AD conversion result
adc_data=ADCH;
Myadcvalue=1;

// Place your code here

}

// Declare your global variables here



void main(void)
{
// Declare your local variables here

// Crystal Oscillator division factor: 1
#pragma optsize-
CLKPR=0x80;
CLKPR=0x00;
#ifdef _OPTIMIZE_SIZE_
#pragma optsize+
#endif

// Input/Output Ports initialization
// Port B initialization
// Func5=In Func4=In Func3=Out Func2=Out Func1=Out Func0=Out 
// State5=T State4=T State3=0 State2=0 State1=0 State0=0 
PORTB=0x00;
DDRB=0x0F;

// Timer/Counter 0 initialization
// Clock source: System Clock
// Clock value: Timer 0 Stopped
// Mode: Normal top=FFh
// OC0A output: Disconnected
// OC0B output: Disconnected
TCCR0A=0x00;
TCCR0B=0x00;
TCNT0=0x00;
OCR0A=0x00;
OCR0B=0x00;

// Timer/Counter 1 initialization
// Clock source: System Clock
// Clock value: 0.244 kHz
// Mode: Normal top=FFh
// OC1A output: Disconnected
// OC1B output: Disconnected
// Timer1 Overflow Interrupt: Off
// Compare A Match Interrupt: On
// Compare B Match Interrupt: Off
PLLCSR=0x00;

TCCR1=0x0D;
GTCCR=0x00;
TCNT1=0x00;
OCR1A=0xF4;
OCR1B=0x00;
OCR1C=0x00;

// External Interrupt(s) initialization
// INT0: Off
// Interrupt on any change on pins PCINT0-5: Off
GIMSK=0x00;
MCUCR=0x00;

// Timer(s)/Counter(s) Interrupt(s) initialization
TIMSK=0x40;

// Universal Serial Interface initialization
// Mode: Disabled
// Clock source: Register & Counter=no clk.
// USI Counter Overflow Interrupt: Off
USICR=0x00;

// Analog Comparator initialization
// Analog Comparator: Off
ACSR=0x80;
ADCSRB=0x00;

// ADC initialization
// ADC Clock frequency: 500.000 kHz
// ADC Voltage Reference: 2.56V, AREF discon.
// ADC Bipolar Input Mode: Off
// ADC Reverse Input Polarity: Off
// ADC Auto Trigger Source: ADC Stopped
// Only the 8 most significant bits of
// the AD conversion result are used
// Digital input buffers on ADC0: On, ADC1: On, ADC2: Off, ADC3: On
DIDR0&=0x03;
DIDR0|=0x10;
ADMUX=ADC_VREF_TYPE & 0xff;
ADCSRA=0x89;
ADCSRB&=0x5F;

// Global enable interrupts
#asm("sei")

// Wait for timer to tick to next 1 second mark
      secondtimer=0;
      while(secondtimer==0){
      }
while (1)
      {
      // Place your code here  
 
// wait for 1 second and read ADC to find maximum voltage value      
      secondtimer=0;
      maxvalue=0;
      
      while (secondtimer==0)
      {
       Myadcvalue=0;
       ADCSRA = 0b11001000 & 0xff;   
       while(Myadcvalue==0) {
       temp++;
       } 
     if( maxvalue < adc_data )
      {
      maxvalue = adc_data;
      }
      
      }
      
 // test maxvalue here if > 128 then device is on
      
       
      }
}

These Allegro current sensors have a positive only (unipolar) output cenered around the internally generated VCC/2 voltage, so you don't need any clamping etc.