//  A to D test code
// NOTE -- You MUST MOUNT the Aref jumper  

#include <Mega32.h>
#include <stdio.h> 
//I like these definitions
#define begin {
#define end   }  

signed char Ain ; 		//raw A to D number
float Vcc = 4.95;       //Vref
float gain = 10;        //A/D converter diffamp gain

void main(void)
begin 
   //init the A to D converter 
   // left adj /EXTERNAL Aref
   //!!!CONNECT Aref jumper!!!! 
   // 10*(chan1 - chan0)
   ADMUX = 0b00101001;   
   //enable ADC and set prescaler to 1/128*16MHz=125,000
   //and clear interupt enable
   //and start a conversion
   ADCSR = 0b11000111; 
   
   //init the UART
   UCSRB = 0x18;
   UBRRL = 103;
   printf("starting...\n\r");
      
   // measure and display loop
   while (1)
   begin   
	//get the sample  
 	Ain = ADCH;
 	//start another conversion
 	ADCSR.6=1; 
 	//results to hyperterm
 	//for differential inputs the number of effective bits is
 	//dropped because of the sign bit. 
 	// Therefore, divide the ADC value by 128 rather than 256 
 	//also divide by the ADC differential amp gain
  	printf("%f\n\r",(float)Ain/128.0*Vcc/gain);
  end
end