Wiring the 360 Rotary Encoder on C Code & Python

Another illustration that demonstrate using rotary encoder. Rotary encoder is an electro mechanical device that convert the angular position or a motion of a shaft or axle to analog or digital code. Rotary encoder are usually used at the side which is perpendicular to the shaft. They act as sensors for detecting angle, speed, length, position and acceleration in automation field. As you turn the knob you will hear a sound from the knob indicating that one position has been rotated. If the internal contact were originally HIGH after a single click they would now both in LOW state breaking the circuit.

With a simple bit of logic you can work out the direction of the rotation. Most rotary encoder has a 5 pins with 3 functions or tuning left, right and pressing down. Pin 1 and Pin 2 are switch wiring terminals used to press. They are similar to buttons. Pin 4 usually placed in ground and the Pin 3 and Pin 5 are first connected to pull up resistor and then wired to the microcontroller. The diagram below demonstrates the right and left rotation pulse.

Incremental encoder provides two phase square wave, these phase difference are 90 degree, usually called A and B channel. The rotational speed of a channel related information is given, while the two channel signal by comparing the sequence detail obtained in the rotation direction. There is a unique signal called the (Z) or zero channel that provided the absolute encoder zero, this signal is a square wave accord with the center line of the channel (A) square wave.

Accuracy depends on mechanical and electrical factors, these issues are indexing errors, disc eccentricity, bearing eccentric, electronic device errors and inaccuracies introduced by optical parts. The encoder determines the degree of accuracy of the measurement unit and electrical pulses generated by the encoder stars. The following degrees rotation of the mechanical axis to represent, and the axis of rotation must be a complete cycle. You have to know how much the equivalent of a 360 degree electrical angle, you can use these formula to calculate the degree. 360 = 360*/n* pulse / revolution.

Components Required

Raspberry Pi / Banana Pi / Orange Pi (If your using Banana Pi or Orange See first the GPIO Pins)
Rotary Encode
Solder Less Bread Board
Jumper Wire / DuPont Wire

Wiring Guide

C Code / Wiring Pi

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <wiringPi.h> 

#define RotateAPin 4 //Define as CLK
#define RotateBPin 5 // Define as DT
#define SwitchPin 1 // Define as Push Button Switch

static volatile int globalCounter = 0 ;

unsigned char flag;
unsigned char Last_RoB_Status;
unsigned char Current_RoB_Status;

void btnISR(void)
{
globalCounter = 0;
}

void rotaryDeal(void)
{
Last_RoB_Status = digitalRead(RotateBPin);

while(!digitalRead(RotateAPin)){
Current_RoB_Status = digitalRead(RotateBPin);
flag = 1;
}

if(flag == 1){
flag = 0;
if((Last_RoB_Status == 0)&&(Current_RoB_Status == 1)){
globalCounter ++;
}
if((Last_RoB_Status == 1)&&(Current_RoB_Status == 0)){
globalCounter --;
}
}
}

int main(void)
{
if(wiringPiSetup() < 0){
fprintf(stderr, "Unable to initialize wiringPi:%s\n",strerror(errno));
return 1;
}

pinMode(SwitchPin, INPUT);
pinMode(RotateAPin, INPUT);
pinMode(RotateBPin, INPUT);

pullUpDnControl(SwitchPin, PUD_UP);

if(wiringPiISR(SwitchPin, INT_EDGE_FALLING, &btnISR) < 0){
fprintf(stderr, "Unable to init ISR\n",strerror(errno));
return 1;
}

int tmp = 0;

while(1){
rotaryDeal();
if (tmp != globalCounter){
printf("%d\n", globalCounter);
tmp = globalCounter;
}
}

return 0;
}

#include <stdio.h>

#include <string.h>

#include <errno.h>

#include <stdlib.h>

#include <wiringPi.h>

#define RotateAPin 4 //Define as CLK

#define RotateBPin 5 // Define as DT

#define SwitchPin 1 // Define as Push Button Switch

static volatile int globalCounter = 0 ;

unsigned char flag;

unsigned char Last_RoB_Status;

unsigned char Current_RoB_Status;

void btnISR(void)

{

globalCounter = 0;

}

void rotaryDeal(void)

{

Last_RoB_Status = digitalRead(RotateBPin);

while(!digitalRead(RotateAPin)){

Current_RoB_Status = digitalRead(RotateBPin);

flag = 1;

}

if(flag == 1){

flag = 0;

if((Last_RoB_Status == 0)&&(Current_RoB_Status == 1)){

globalCounter ++;

}

if((Last_RoB_Status == 1)&&(Current_RoB_Status == 0)){

globalCounter --;

}

int main(void)

{

if(wiringPiSetup() < 0){

fprintf(stderr, "Unable to initialize wiringPi:%s\n",strerror(errno));

return 1;

}

pinMode(SwitchPin, INPUT);

pinMode(RotateAPin, INPUT);

pinMode(RotateBPin, INPUT);

pullUpDnControl(SwitchPin, PUD_UP);

if(wiringPiISR(SwitchPin, INT_EDGE_FALLING, &btnISR) < 0){

fprintf(stderr, "Unable to init ISR\n",strerror(errno));

return 1;

}

int tmp = 0;

while(1){

rotaryDeal();

if (tmp != globalCounter){

printf("%d\n", globalCounter);

tmp = globalCounter;

}

return 0;

}

Python Code

#!/usr/bin/env python
import RPi.GPIO as GPIO
import time

RotateAPin = 16 # Define as CLK Pin
RotateBPin = 18 # Define as DT Pin
SwitchPin = 12 # Define as Push Button Pin

globalCounter = 0

flag = 0
Last_RoB_Status = 0
Current_RoB_Status = 0

def setup():
GPIO.setmode(GPIO.BOARD) # Set GPIO pin as numbered
GPIO.setup(RotateAPin, GPIO.IN) # Set to input mode
GPIO.setup(RotateBPin, GPIO.IN) # Set to input mode
GPIO.setup(SwitchPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

def rotaryDeal():
global flag
global Last_RoB_Status
global Current_RoB_Status
global globalCounter
Last_RoB_Status = GPIO.input(RotateBPin)
while(not GPIO.input(RotateAPin)):
Current_RoB_Status = GPIO.input(RotateBPin)
flag = 1
if flag == 1:
flag = 0
if (Last_RoB_Status == 0) and (Current_RoB_Status == 1):
globalCounter = globalCounter + 1
if (Last_RoB_Status == 1) and (Current_RoB_Status == 0):
globalCounter = globalCounter - 1

def btnISR(channel):
global globalCounter
globalCounter = 0

def loop():
global globalCounter
tmp = 0 # Rotary Temperary

GPIO.add_event_detect(SwitchPin, GPIO.FALLING, callback=btnISR)
while True:
rotaryDeal()
if tmp != globalCounter:
print 'globalCounter = %d' % globalCounter
tmp = globalCounter

def destroy():
GPIO.cleanup() # Release resource

if __name__ == '__main__': # Program start from here
setup()
try:
loop()
except KeyboardInterrupt: # When 'Ctrl+C' is pressed, the child program destroy() will be executed.
destroy()

#!/usr/bin/env python

import RPi.GPIO as GPIO

import time

RotateAPin = 16 # Define as CLK Pin

RotateBPin = 18 # Define as DT Pin

SwitchPin = 12 # Define as Push Button Pin

globalCounter = 0

flag = 0

Last_RoB_Status = 0

Current_RoB_Status = 0

def setup():

GPIO.setmode(GPIO.BOARD) # Set GPIO pin as numbered

GPIO.setup(RotateAPin, GPIO.IN) # Set to input mode

GPIO.setup(RotateBPin, GPIO.IN) # Set to input mode

GPIO.setup(SwitchPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

def rotaryDeal():

global flag

global Last_RoB_Status

global Current_RoB_Status

global globalCounter

Last_RoB_Status = GPIO.input(RotateBPin)

while(not GPIO.input(RotateAPin)):

Current_RoB_Status = GPIO.input(RotateBPin)

flag = 1

if flag == 1:

flag = 0

if (Last_RoB_Status == 0) and (Current_RoB_Status == 1):

globalCounter = globalCounter + 1

if (Last_RoB_Status == 1) and (Current_RoB_Status == 0):

globalCounter = globalCounter - 1

def btnISR(channel):

global globalCounter

globalCounter = 0

def loop():

global globalCounter

tmp = 0 # Rotary Temperary

GPIO.add_event_detect(SwitchPin, GPIO.FALLING, callback=btnISR)

while True:

rotaryDeal()

if tmp != globalCounter:

print 'globalCounter = %d' % globalCounter

tmp = globalCounter

def destroy():

GPIO.cleanup() # Release resource

if __name__ == '__main__': # Program start from here

setup()

try:

loop()

except KeyboardInterrupt: # When 'Ctrl+C' is pressed, the child program destroy() will be executed.

destroy()

Downloads

Download TW700198 Rotary Encoder Datasheet | PDF

Wiring the 360 Rotary Encoder on C Code & Python

Tagged on: #fourteencore #fourtencore 14CORE 37 - Sensor 37 in 1 Module 37-1 Raspbberry Pi Raspberry Raspberry Pi Starter Sensor Kit

2 thoughts on “Wiring the 360 Rotary Encoder on C Code & Python”

shameerariff
at

Why this C program is consuming almost 100% CPU
- Wired DeveloperPost author
  at
  
  Chick the code line While and should be return to 0 ) or perhaps there is a technical issues in your rotary coder.

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2 thoughts on “Wiring the 360 Rotary Encoder on C Code & Python”

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