Reading Arduino Inputs to a Binary Number

In one of my recent projects, I had to read a few digital inputs of an Arduino board into an integer variable as a binary number. My initial thought was to use direct register addressing, but later on, I came up with two other methods which work really well. Here on my blog, I share all three of them, hoping that these would help someone else as well.

Note: Pull down resistors MUST be used for each example.

1. Only using digitalRead()

 void setup() {  
  Serial.begin(9600);  
  pinMode(2,INPUT);  
  pinMode(3,INPUT);  
  pinMode(4,INPUT);  
  pinMode(5,INPUT);  
 }  
 void loop() {  
   int b0 = digitalRead(2);  
   int b1 = digitalRead(3);  
   int b2 = digitalRead(4);  
   int b3 = digitalRead(5);  
   int output=b0+(2*b1)+(4*b2)+(8*b3); //create the binary number  
   Serial.println(output);  
   delay(100);  
 }  

2. Using BitShiftLeft (<<)

 void setup() {  
  Serial.begin(9600);  
  pinMode(2,INPUT);  
  pinMode(3,INPUT);  
  pinMode(4,INPUT);  
  pinMode(5,INPUT);  
 }  
 void loop() {  
   int b0 = digitalRead(2);  
   int b1 = digitalRead(3);  
   int b2 = digitalRead(4);  
   int b3 = digitalRead(5);  
   b1=b1<<1; //Shift the second bit by one binary place  
   b2=b2<<2; //Shift the third bit by two binary places  
   b3=b3<<3; //Shift the fourth bit by three binary places  
   int output=b0+b1+b2+b3; //add them together  
   Serial.println(output);  
   delay(100);  
 }  

3. Reading the registers directly - Simplest method so far

In AVR microcontrollers, there is a register called Chip Register, which stores the input value of a particular group of pins (a port). In This example, Chip register is read and assigned directly to an int variable.

 void setup() {  
 Serial.begin(9600);  
 }  
 void loop() {  
 DDRC=0x00; //Set all the pins of PortC to be inputs (A0 to A5 on Arduino Uno)  
 int a=PINC; //Read the input pins directly into a binary number   
 Serial.println(a);  
 delay(500);  
 }  

This last code is amazingly simple, and lightweight.  It could be way more useful when combined with Arduino Core functions.