# interface incremental encoder with interrupts
# raspberry pi pico and micropython
# Firmware : MicroPython v1.14 on 2021-02-02; Raspberry Pi Pico with RP2040
 
# import libraries
from machine import Pin, PWM
import utime 

# initial varibale declaratins
frequency = 50 # 50 hz frequency for servo , change it according to manufacturer's specification
pwm_duty_cycle = 0 # initialize duty cycle to 0 %

# define encoder pins
switch = Pin(16, mode=Pin.IN, pull = Pin.PULL_UP) # inbuilt switch on the rotary encoder, ACTIVE LOW
outA = Pin(17, mode=Pin.IN) # Pin CLK of encoder
outB = Pin(18, mode=Pin.IN) # Pin DT of encoder

# define servo pin and construct servo object
pwmPin = Pin(15) # declare the pin for PWM output
servo = PWM(pwmPin) # define a servo object
servo.freq(frequency) # set pwm frequency

# define global variables
counter = 0   # counter updates when encoder rotates
direction = "" # empty string for registering direction change
outA_last = 0 # registers the last state of outA pin / CLK pin
outA_current = 0 # registers the current state of outA pin / CLK pin
button_last_state = False # initial state of encoder's button 
button_current_state = "" # empty string ---> current state of button
button_pressed = False

# Read the last state of CLK pin in the initialisaton phase of the program 
outA_last = outA.value() 


# interrupt handler function (IRQ) for CLK and DT pins
def encoder(pin):
    # get global variables
    global counter
    global direction
    global outA_last
    global outA_current
    
    # read the value of current state of outA pin / CLK pin
    outA_current = outA.value()
    
    # if current state is not same as the last stare , encoder has rotated
    if outA_current != outA_last:
        # read outB pin/ DT pin
        # if DT value is not equal to CLK value
        # rotation is clockwise [or Counterclockwise ---> sensor dependent]
        if outB.value() != outA_current:
            counter += 1
            direction = True
        else:
            counter -= 1
            direction = False
        
        # print the data on screen
        print("Counter : ", counter, "     |   Direction : ",direction)
        print("\n")
    
    # update the last state of outA pin / CLK pin with the current state
    outA_last = outA_current
    utime.sleep_ms(1) # small time delay to make the interrupt routine little
                       # more stable and to avoid multiple countings, optional
    

# interrupt handler function (IRQ) for SW (switch) pin


    
# Attach interrupt to Pins
""" If you need to write a program which triggers an interrupt whenever
    a pin changes, without caring whether it’s rising or falling,
    you can combine the two triggers using a pipe or
    a vertical bar symbol ( | ) . Logical AND """

# attach interrupt to the outA pin ( CLK pin of encoder module )
outA.irq(trigger = Pin.IRQ_RISING | Pin.IRQ_FALLING,
         handler = encoder)

# attach interrupt to the outB pin ( DT pin of encoder module )
outB.irq(trigger = Pin.IRQ_RISING | Pin.IRQ_FALLING ,
         handler = encoder)

# attach interrupt to the switch pin ( SW pin of encoder module )



# function for asking duty_cycle input for servo
def angle(counts):
    """ converts encoder's rotation (counter) value to corresponding duty cycle of
        the PWM signal """
    encoderClicks = counts
    
    if encoderClicks >= 0 and encoderClicks <= 180:
        angleDegree = encoderClicks 
        
        # full range of PWM : 0 - 65025 
        # convert angle to micropython range 1950 - 7803
                        #  Duty Cycle of  3 %  - 12 %
        duty_cycle = int(angleDegree*(7803-1950)/180) + 1950
        
        return duty_cycle, angleDegree # returns the duty cycle (in integer)
    
    elif encoderClicks < 0:
        """ 1950 = duty cycle for 0 degree position , depends on model """
        return 1950, 0
    
    else :
        """ 7803 = duty cycle for 180 degree position , depends on model """
        return 7803, 180

# main logic
while True:
    utime.sleep(1)# reduce it to 0.1 second to make servo response faster
    
    # get pwm duty cycle
    pwm_duty_cycle, angleDegree = angle(counter) # global variable counter
        
    if button_pressed == True:
        # set pwm duty cycle
        servo.duty_u16(pwm_duty_cycle)
        print("angle moved = ", angleDegree , " Degree")
        button_pressed = False
   
    """ to avoid multiple button press registration with interrupts """
    button_last_state = False # reset button last state to false again ,
                              # totally optional and application dependent,
                              # can also be done from other subroutines
                              # or from the main loop