unsigned long s_start = 0;
unsigned long s_stop  = 0;
unsigned long extime  = 0;
byte readDDRAfirst = 0;
byte readDDRAsecond = 0;
byte readDDRAthird = 0;
byte readDDRAfourth = 0;
byte readPORTAfirst = 0;
byte readPORTAsecond = 0;
byte readPORTAthird = 0;
byte readPORTAfourth = 0;
byte readPINAfirst = 0;
byte readPINAsecond = 0;
byte readPINAthird = 0;
byte readPINAfourth = 0;

char* b2s(byte var) {
   static char Str[8];
   byte mask = 0b10000000;
   for(int i = 0; i<8; i++){
     Str[i]='0';
     if(((mask >> i) & var) == (mask>>i)){Str[i]='1';     }
   }
   Str[8] = '\0';
   return Str;
}

void setup() {
    while(!Serial);
    Serial.begin(115200);
    Serial.println("Arduino ready for SDS7");
    //pin 29-22
    DDRA = DDRA | 0b00000000; //0=output 1=input
    PORTA = 0;
    DDRA = DDRA | 0b11111111; //0=output 1=input
}

void loop() {
  s_start = micros();
  
  //Set port A to inputs in high-impedance state
  //pin 29-22
  DDRA = 0b11111111; //0=output 1=input
  readDDRAfirst = DDRA;
  readPORTAfirst = PORTA;
  readPINAfirst = PINA;
  
  //Set port A to output and alter some pins
  //pin 29-22
  DDRA = 0b00000000; //0=output 1=input
  PORTA = B00111010;
  readDDRAsecond = DDRA;
  readPORTAsecond = PORTA;
  readPINAsecond = PINA; 
  
  //Set port A back to high-impedance input state and read 
  //pin 29-22
  DDRA = 0b11111111; //0=output 1=input
  readDDRAthird = DDRA;  
  readPORTAthird = PORTA;
  readPINAthird = PINA;

  //Try to reset port while set to input
  PORTA = 0;
  readDDRAfourth = DDRA;  
  readPORTAfourth = PORTA;
  readPINAfourth = PINA;
 
  s_stop = micros();
  extime = s_stop - s_start;

  Serial.println("------------------------------------");    
  Serial.print("Execution time: "); Serial.print(extime); Serial.println(" micro seconds");
  Serial.println("------------------------------------");  
  Serial.println("        DDRA      PORTA     PINA");
  Serial.print("Input:  "); 
    Serial.print(b2s(readDDRAfirst)); Serial.print("  "); 
    Serial.print(b2s(readPORTAfirst)); Serial.print("  ");
    Serial.println(b2s(readPINAfirst));
  Serial.print("Output: "); 
    Serial.print(b2s(readDDRAsecond)); Serial.print("  "); 
    Serial.print(b2s(readPORTAsecond)); Serial.print("  ");
    Serial.println(b2s(readPINAsecond));
  Serial.print("Input:  "); 
    Serial.print(b2s(readDDRAthird)); Serial.print("  "); 
    Serial.print(b2s(readPORTAthird)); Serial.print("  ");
    Serial.println(b2s(readPINAthird));  
  Serial.print("Input:  "); 
    Serial.print(b2s(readDDRAfourth)); Serial.print("  "); 
    Serial.print(b2s(readPORTAfourth)); Serial.print("  ");
    Serial.println(b2s(readPINAfourth));  
  Serial.println("");    
  Serial.println("1th Port A is set to high-impedance inputs");
  Serial.println("2th Port direction is set to outputs and some pins altered");
  Serial.println("3th Port is back to inputs, but as seen no longer in");
  Serial.println("high-impedance. It seams port sets pull-ups and leave ");
  Serial.println("them even when DDR (data direction register) change");
  Serial.println("4th same as 3th but PORTA=0 turns off all pull-ups");
  Serial.println(""); 
  delay(3000);
}