Raspberry PI Rotary Encoder Function Example

rpi_rotary_encoder.c

/*

Wiring
  01 3.3V DC POWER --------------- +
  06 GROUND ---------------------- GND
  11 GPIO17 (GPIO_GEN0) ---------- CLK
  12 GPIO18 (GPIO_GEN1) ---------- DT
  13 GPIO19 (GPIO_GEN2) ---------- SW

Compile:
   gcc -Wall -lwiringPi rotary_encoder_example.c -o rotary_encoder_example.bin
   
Run:
   ./rotary_encoder_example.bin
*/

#include <stdio.h>
#include <wiringPi.h>

// pin wiring
#define  PIN_CLK  0
#define  PIN_DT   1
#define  PIN_SW   2

// rotaryRead statuses
#define ROTATION_NONE   0
#define ROTATION_LEFT   1
#define ROTATION_RIGHT  2
#define ROTATION_BUTTON 3

void rotarySetup(int pin_clk, int pin_dt, int pin_sw) {
	// pin configuration
	pinMode(pin_clk, INPUT);
	pinMode(pin_dt, INPUT);
	pinMode(pin_sw, INPUT);

	pullUpDnControl(pin_sw, PUD_UP);
}

int rotaryRead(int pin_clk, int pin_dt, int pin_sw) {
	// read DT status
	int last_dt_status = digitalRead(pin_dt);
	
	int current_dt_status = 0;
	int flag_change = 0;
	
	while(digitalRead(pin_clk) == 0){
		// read DT while CLK equals 0
		current_dt_status = digitalRead(pin_dt);
		flag_change = 1;
	}

	if(flag_change == 1){
		if(last_dt_status==0 && current_dt_status==1){
			return ROTATION_LEFT;
		}
		if(last_dt_status==1 && current_dt_status==0){
			return ROTATION_RIGHT;
		}
	}
	
	if(digitalRead(pin_sw) == 0){
		delay(200);
		return ROTATION_BUTTON;
	}
	
	return ROTATION_NONE;
}

int main(void) {
	
	if(wiringPiSetup() < 0){
		printf("ERROR:  wiringPiSetup \n");
		return 1;
	}

	rotarySetup(PIN_CLK, PIN_DT, PIN_SW);
	
	while(1){
		
		int stat = rotaryRead(PIN_CLK, PIN_DT, PIN_SW);
		
		if(stat != ROTATION_NONE) {
			if(stat == ROTATION_LEFT) {
				printf("left \n");
			}
			if(stat == ROTATION_RIGHT) {
				printf("right \n");
			}
			if(stat == ROTATION_BUTTON) {
				printf("button \n");
			}
		}
	}
  
	return 0;
}