Arduino with rotary encoder and 7 segment display

his topic shows how to connect Arduino UNO with rotary encoder and 7-segment display. Here the rotary encoder is an input device and the 7-segment display is an output device. The 7-segment display prints the values of the rotary encoder (positive or negative) on 4 digits where the first digit (most left) is used for the minus sign ( -). To see how to connect Arduino with 7-segment display visit the following post: Interfacing Arduino with 7-segment display | 4-Digit counter example To see how the rotary encoder works and how to interface it with Arduino in order to control a DC motor speed, take a look at the project below: DC Motor control with rotary encoder and Arduino Parts Required:

Arduino UNO board —> ATmega328P datasheet
4-Digit common anode 7-segment display
4 x PNP transistor (2SA1015, 2S9015, 2N3906 …)
Rotary encoder
7 x 100 ohm resistor
4 x 4.7k ohm resistor
Breadboard
Jumper wires

Arduino with rotary encoder and 7-segment display circuit: The image below shows example circuit schematic diagram.

The rotary encoder board has 5 pins: GND, + , SW, DT (pin B or data pin) and CLK (pin A or clock pin) where: GND is connected to Arduino GND pin + is connected to Arduino 5V pin SW is push button pin, not used in this example DT is connected to Arduino analog pin 5 (A5) CLK is connected to Arduino analog pin 4 (A4) The 4 transistors are of the same type (PNP).

Arduino with rotary encoder and 7 segment display code: The Arduino code below doesn’t use any library for the 7-segment display. The rotary encoder pin A (CLK) and pin B (DT) are connected to Arduino UNO pins A4 and A5 respectively. Both pins can be used to interrupt the Arduino microcontroller (ATmega328P) whenever there is a change in the state of at least one pin. The following lines are used to enable interrupt-on-change for pins A4 (PCINT12) and A5 (PCINT13):

// pin change interrupt configuration

PCICR = 2; // enable pin change interrupt for pins PCINT14..8 (Arduino A0 to A5)

PCMSK1 = 0x30; // enable pin change interrupt for pins PCINT12 & PCINT13 (Arduino A4 & A5)

Since the 4 digits are multiplexed we need to refresh the display very quickly (display one digit at a time, others are off). For that I used Timer1 module interrupt with the following configuration:

// Timer1 module overflow interrupt configuration

TCCR1A = 0;

TCCR1B = 1; // enable Timer1 with prescaler = 1 ( 16 ticks each 1 µs)

TCNT1 = 0; // set Timer1 preload value to 0 (reset)

TIMSK1 = 1; // enable Timer1 overflow interrupt

With the above configuration Timer1 module overflows every 4096 microseconds (4096 = 65536/16). Note that Timer1 module is 16-bit timer, prescaler = 1 (TCCR1B = 1) and Arduino UNO clock = 16MHz. Full Arduino code:

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* Interfacing Arduino with common anode 7-segment display.

* Print rotary encoder values on 4-digit 7-segment display.

* This is a free software with NO WARRANTY.

* http://simple-circuit.com/

// segment pin definitions

#define SegA 12

#define SegB 11

#define SegC 10

#define SegD 9

#define SegE 8

#define SegF 7

#define SegG 6

// common pins of the four digits definitions

#define Dig1 5

#define Dig2 4

#define Dig3 3

#define Dig4 2

// variable declarations

byte current_digit, last_read;

int8_t quad = 0, change;

int enc_value = 0;

void setup()

{

pinMode(SegA, OUTPUT);

pinMode(SegB, OUTPUT);

pinMode(SegC, OUTPUT);

pinMode(SegD, OUTPUT);

pinMode(SegE, OUTPUT);

pinMode(SegF, OUTPUT);

pinMode(SegG, OUTPUT);

pinMode(Dig1, OUTPUT);

pinMode(Dig2, OUTPUT);

pinMode(Dig3, OUTPUT);

pinMode(Dig4, OUTPUT);

pinMode(A4, INPUT_PULLUP);

pinMode(A5, INPUT_PULLUP);

last_read = digitalRead(A5) << 1 | digitalRead(A4);

disp_off(); // turn off the display

// Timer1 module overflow interrupt configuration

TCCR1A = 0;

TCCR1B = 1; // enable Timer1 with prescaler = 1 ( 16 ticks each 1 µs)

TCNT1 = 0; // set Timer1 preload value to 0 (reset)

TIMSK1 = 1; // enable Timer1 overflow interrupt

// pin change interrupt configuration

PCICR = 2; // enable pin change interrupt for pins PCINT14..8 (Arduino A0 to A5)

PCMSK1 = 0x30; // enable pin change interrupt for pins PCINT12 & PCINT13 (Arduino A4 & A5)

}

ISR(TIMER1_OVF_vect) // Timer1 interrupt service routine (ISR)

{

disp_off(); // turn off the display

uint16_t abs_value = abs(enc_value); // abs: absolute value

switch (current_digit)

{

case 1:

if(enc_value < 0) // if negative value

{ // print minus sign (-) on digit 1 (most left digit)

disp(10); // prepare to display digit 1

digitalWrite(Dig1, LOW); // turn on digit 1

}

break;

case 2:

disp( (abs_value / 100) % 10); // prepare to display digit 2

digitalWrite(Dig2, LOW); // turn on digit 2

break;

case 3:

disp( (abs_value / 10) % 10); // prepare to display digit 3

digitalWrite(Dig3, LOW); // turn on digit 3

break;

case 4:

disp(abs_value % 10); // prepare to display digit 4 (most right)

digitalWrite(Dig4, LOW); // turn on digit 4

}

current_digit = (current_digit % 4) + 1;

}

ISR (PCINT1_vect) // ISR for Arduino A4 (PCINT12) and A5 (PCINT13) pins

{

uint8_t encoderRead = 0;

encoderRead = digitalRead(A5) << 1 | digitalRead(A4);

if(encoderRead == last_read)

return;

if(bitRead(encoderRead, 0) == bitRead(last_read, 1))

quad -= 1;

else

quad += 1;

last_read = encoderRead;

}

int8_t EncoderGet(void)

{

int8_t val = 0;

while(quad >= 4){

val += 1;

quad -= 4;

}

while(quad <= -4){

val -= 1;

quad += 4;

}

return val;

}

// main loop

void loop()

{

change = EncoderGet();

if(change)

enc_value += change;

delay(100); // wait 100 milliseconds

}

void disp(byte number)

{

switch (number)

{

case 0: // print 0

digitalWrite(SegA, LOW);

digitalWrite(SegB, LOW);

digitalWrite(SegC, LOW);

digitalWrite(SegD, LOW);

digitalWrite(SegE, LOW);

digitalWrite(SegF, LOW);

digitalWrite(SegG, HIGH);

break;

case 1: // print 1

digitalWrite(SegA, HIGH);

digitalWrite(SegB, LOW);

digitalWrite(SegC, LOW);

digitalWrite(SegD, HIGH);

digitalWrite(SegE, HIGH);

digitalWrite(SegF, HIGH);

digitalWrite(SegG, HIGH);

break;

case 2: // print 2

digitalWrite(SegA, LOW);

digitalWrite(SegB, LOW);

digitalWrite(SegC, HIGH);

digitalWrite(SegD, LOW);

digitalWrite(SegE, LOW);

digitalWrite(SegF, HIGH);

digitalWrite(SegG, LOW);

break;

case 3: // print 3

digitalWrite(SegA, LOW);

digitalWrite(SegB, LOW);

digitalWrite(SegC, LOW);

digitalWrite(SegD, LOW);

digitalWrite(SegE, HIGH);

digitalWrite(SegF, HIGH);

digitalWrite(SegG, LOW);

break;

case 4: // print 4

digitalWrite(SegA, HIGH);

digitalWrite(SegB, LOW);

digitalWrite(SegC, LOW);

digitalWrite(SegD, HIGH);

digitalWrite(SegE, HIGH);

digitalWrite(SegF, LOW);

digitalWrite(SegG, LOW);

break;

case 5: // print 5

digitalWrite(SegA, LOW);

digitalWrite(SegB, HIGH);

digitalWrite(SegC, LOW);

digitalWrite(SegD, LOW);

digitalWrite(SegE, HIGH);

digitalWrite(SegF, LOW);

digitalWrite(SegG, LOW);

break;

case 6: // print 6

digitalWrite(SegA, LOW);

digitalWrite(SegB, HIGH);

digitalWrite(SegC, LOW);

digitalWrite(SegD, LOW);

digitalWrite(SegE, LOW);

digitalWrite(SegF, LOW);

digitalWrite(SegG, LOW);

break;

case 7: // print 7

digitalWrite(SegA, LOW);

digitalWrite(SegB, LOW);

digitalWrite(SegC, LOW);

digitalWrite(SegD, HIGH);

digitalWrite(SegE, HIGH);

digitalWrite(SegF, HIGH);

digitalWrite(SegG, HIGH);

break;

case 8: // print 8

digitalWrite(SegA, LOW);

digitalWrite(SegB, LOW);

digitalWrite(SegC, LOW);

digitalWrite(SegD, LOW);

digitalWrite(SegE, LOW);

digitalWrite(SegF, LOW);

digitalWrite(SegG, LOW);

break;

case 9: // print 9

digitalWrite(SegA, LOW);

digitalWrite(SegB, LOW);

digitalWrite(SegC, LOW);

digitalWrite(SegD, LOW);

digitalWrite(SegE, HIGH);

digitalWrite(SegF, LOW);

digitalWrite(SegG, LOW);

break;

case 10: // print -

digitalWrite(SegA, HIGH);

digitalWrite(SegB, HIGH);

digitalWrite(SegC, HIGH);

digitalWrite(SegD, HIGH);

digitalWrite(SegE, HIGH);

digitalWrite(SegF, HIGH);

digitalWrite(SegG, LOW);

}

void disp_off()

{

digitalWrite(Dig1, HIGH);

digitalWrite(Dig2, HIGH);

digitalWrite(Dig3, HIGH);

digitalWrite(Dig4, HIGH);

}

// end of code.

The following small video shows a test circuit of this project:

Arduino with rotary encoder and 7 segment display

Arduino with rotary encoder and 7 segment display

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