RPI Robotic Arm

import RPi.GPIO as GPIO
import pigpio
GPIO.setmode(GPIO.BCM)
from time import sleep
import sys, tty, termios, time
import time
GPIO.setwarnings(False)

pi = pigpio.pi()
user_gpio = 0-31.
pulsewidth = 0, 500-2500

# Variables

delay = 0.02
steps = 200
refresh_period = 0.02

# Enable servo pins and variables
spwm = 1500
epwm = 1500
wpwm = 1500
g1pwm = 1200
g2pwm = 1800

nspwm = 1500
nepwm = 1500
nwpwm = 1500
ng1pwm = 1200
ng2pwm = 1800

shoulderpin = 18
elbowpin = 12
wristpin = 16
grip1pin = 20
grip2pin = 21

GPIO.setup(shoulderpin, GPIO.OUT)
GPIO.setup(elbowpin, GPIO.OUT)
GPIO.setup(wristpin, GPIO.OUT)
GPIO.setup(grip1pin, GPIO.OUT)
GPIO.setup(grip2pin, GPIO.OUT)

# Enable pins for IN1-4 to control step sequence in stepper motor

coil_1_pin = 23
coil_2_pin = 24
coil_3_pin = 22
coil_4_pin = 17

# Set pin states for stepper motor

GPIO.setup(coil_1_pin, GPIO.OUT)
GPIO.setup(coil_2_pin, GPIO.OUT)
GPIO.setup(coil_3_pin, GPIO.OUT)
GPIO.setup(coil_4_pin, GPIO.OUT)

# The getch method can determine which key has been pressed
# by the user on the keyboard by accessing the system files
# It will then return the pressed key as a variable
def getch():
    fd = sys.stdin.fileno()
    old_settings = termios.tcgetattr(fd)
    try:
        tty.setraw(sys.stdin.fileno())
        ch = sys.stdin.read(1)
    finally:
        termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
    return ch

# This section of code defines the methods used to move
# the stepper turning motor and servos used for manipulating
# the arm. These definitions are called later by keypress events.


def turn_right():
    GPIO.output(23, 1)
    sleep(0.02)
    GPIO.output(23, 0)
    GPIO.output(24, 1)
    sleep(0.02)
    GPIO.output(24, 0)
    GPIO.output(22, 1)
    sleep(0.02)
    GPIO.output(22, 0)
    GPIO.output(17, 1)
    sleep(0.02)
    GPIO.output(17, 0)

def turn_left():
    GPIO.output(17, 1)
    sleep(0.02)
    GPIO.output(17, 0)
    GPIO.output(22, 1)
    sleep(0.02)
    GPIO.output(22, 0)
    GPIO.output(24, 1)
    sleep(0.02)
    GPIO.output(24, 0)
    GPIO.output(23, 1)
    sleep(0.02)
    GPIO.output(23, 0)

def shoulder_up(spwm = spwm, nspwm = nspwm):
    for spwm in range(1000, 2000, 20):
        pi.set_servo_pulsewidth(shoulderpin, spwm)
        time.sleep(0.4)
        pi.set_servo_pulsewidth(shoulderpin, 0)
def shoulder_down(spwm = spwm, nspwm = nspwm):
    spwm = nspwm
    pi.set_servo_pulsewidth(shoulderpin, spwm)
    time.sleep(0.4)
    pi.set_servo_pulsewidth(shoulderpin, 0)    # off
    nspwm = spwm + 20
def elbow_up():
    epwm = epwm + 20
    pi.set_servo_pulsewidth(elbowpin, 1500)
    time.sleep(0.4)
    pi.set_servo_pulsewidth(elbowpin, 0)    # off

def elbow_down():
    pi.set_servo_pulsewidth(elbowpin, 2000)
    time.sleep(0.4)
    pi.set_servo_pulsewidth(elbowpin, 0)    # off

def wrist_clockwise():
    pi.set_servo_pulsewidth(wristpin, 1000)
    time.sleep(0.4)
    pi.set_servo_pulsewidth(wristpin, 0)    # off

def wrist_counterclockwise():
    pi.set_servo_pulsewidth(wristpin, 1200)
    time.sleep(0.4)
    pi.set_servo_pulsewidth(wristpin, 0)    # off

def grip_closed():
    pi.set_servo_pulsewidth(grip1pin, 1450)
    pi.set_servo_pulsewidth(grip2pin, 1650)
    time.sleep(0.2)
    pi.set_servo_pulsewidth(grip1pin, 0)    # off
    pi.set_servo_pulsewidth(grip2pin, 0)    # off

def grip_open():
    pi.set_servo_pulsewidth(grip1pin, 1800)
    pi.set_servo_pulsewidth(grip2pin, 1200)
    time.sleep(0.2)
    pi.set_servo_pulsewidth(grip1pin, 0)    # off
    pi.set_servo_pulsewidth(grip2pin, 0)    # off

# Infinite loop that will not end until the user presses the
# exit key
while True:
    # Keyboard character retrieval method is called and saved
    # into variable
    char = getch()

    # The shoulder will move down when the "w" key is pressed
    if(char == "w"):
        shoulder_down()

    # The shoulder will move up when the "s" key is pressed
    if(char == "s"):
        shoulder_up()

    # The "a" key will turn the arm left
    if(char == "a"):
        turn_left()

    # The "d" key will turn the arm right
    if(char == "d"):
        turn_right()

    # The "r" key will move the elbow down
    if(char == "r"):
        elbow_down()

    # The "f" key will move the elbow up
    if(char == "f"):
        elbow_up()

    # The "q" key will turn the wrist counterclockwise
    if(char == "q"):
        wrist_counterclockwise()

    # The "e" key will turn the wrist clockwise
    if(char == "e"):
        wrist_clockwise()

    # The "o" key will open the gripper
    if(char == "o"):
        grip_open()

    # The "p" key will close the gripper
    if(char == "p"):
        grip_closed()

    # The "x" key will break the loop and exit the program
    if(char == "x"):
        print("Program Ended")
        break

    # At the end of each loop

    # The keyboard character variable will be set to blank, ready
    # to save the next key that is pressed
    char = ""

# Program will cease all GPIO activity before terminating
GPIO.cleanup()