avrdice.c

#include <avr/io.h>
#include <util/delay.h>
#include <stdlib.h>
#include <avr/sleep.h>
#include <avr/interrupt.h>

uint16_t ADC_Read( uint8_t channel )
{
  ADMUX = (ADMUX & ~(0x1F)) | (channel & 0x1F);
  ADCSRA |= (1<<ADSC);
  while (ADCSRA & (1<<ADSC) ) {
  }
  return ADCW;
}

uint16_t ADC_rand(uint8_t channel){
  uint16_t out=0;
  for(uint16_t i=0; i<16; ++i){
    out<<=1;
    out|=(ADC_Read(channel)&1);
  }
  return out;
}

void showBNum(uint8_t num) {
  for (uint8_t i = 0; i < 0xff; ++i) //Note: this PWM loop is a software fix for using wrong resistor values
  {
    PORTD = ~num;
    _delay_us(30);
    PORTD = 0xff;
    _delay_ms(2);
  }
}

void showFNum(uint8_t num) {
  showBNum(~(0xff<<num));
}

int main (void) {
  ADMUX = (1<<REFS1) | (1<<REFS0);
  ADCSRA = (1<<ADPS1) | (1<<ADPS0);
  ADCSRA |= (1<<ADEN);

  PORTD=0xff;
  DDRD =0xFF;
  PORTB=0b110;
  _delay_ms(1);

  uint8_t dip= (~PINB>>1) & 3;

  uint8_t rfc1149_5=dip&1;
  uint8_t countable=dip>>1;

  for (int i = 0; i < 16; ++i)
  {
    srand((ADC_rand(0)
      ^ ADC_rand(1)
      ^ ADC_rand(2)
      ^ ADC_rand(3)
      ^ ADC_rand(4)
      ^ ADC_rand(5)
      ^ rand())
      +i
    );
  }
  
  ADCSRA = 0;

  uint8_t value;
  if(rfc1149_5){
    value=4;
  }else{
    value=rand();
  }

  if(countable){
    showFNum(value%9);
  }else{
    showBNum(value);
  }

  PORTB=0;
  DDRD=0;

  while(1){
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
    sleep_enable();
    cli();
    sleep_cpu();
  }
  return 0;
}