A simple set of interfaces to control various servos using RPi.GPIO with preset settings for a couple popular servos

servo_pwm.py

#!/usr/bin/python

import RPi.GPIO as GPIO
import time

def setup():
  GPIO.setmode(GPIO.BCM)
  GPIO.setup(26, GPIO.OUT)

class ServoControl:
  pin = 0
  hz = 0
  min_us = 0
  max_us = 0
  range_deg = 0
  p = None
  
  def  __init__(self, pin = 0, hz = 50, min_us = 450, max_us = 2450, range_deg=60):
    self.pin = pin
    self.hz = hz
    self.min_us = min_us
    self.max_us = max_us
    self.range_deg = range_deg
    return
  
  def copy(self, pin):
    result = ServoControl()
    result.pin = pin
    result.hz = self.hz
    result.min_us = self.min_us
    result.max_us = self.max_us
    result.range_deg = self.range_deg
    return result
  
  def getDCPercent(self, percent_in):
  # Translate a percent of the overall travel (range 0-100) to the percent of duty cycle
    goal_us = self.min_us + percent_in /100.0 * (self.max_us - self.min_us)
    range_us = self.max_us - self.min_us
    duty_cycle_us = 1000000.0/self.hz
    base_pct = self.min_us * 1.0 / duty_cycle_us
    marginal_pct = 0.01 * range_us * percent_in / duty_cycle_us 
    result_pct = base_pct + marginal_pct
    return result_pct
  
  def setDegrees(self, degrees_in):
    target_percent = degrees_in * 100.0 / self.range_deg
    self.setPercent(target_percent)
  
  def setPercent(self, percent_in):
    dc_percent = self.getDCPercent(percent_in)
#    print("percent in:")
#    print(percent_in)
#    print("equals")
#    print(dc_percent)
    self.p.ChangeDutyCycle(dc_percent * 100.0)
    
  def start(self, start_percent = 0):
    GPIO.setup(self.pin, GPIO.OUT)
    self.p = GPIO.PWM(self.pin, self.hz)
    self.p.start(self.getDCPercent(start_percent))
    
  def stop(self):
    self.p.stop()
    
SERVO_HTX_900 = ServoControl()
SERVO_DS3218 = ServoControl(hz = 50, min_us = 800, max_us = 2200, range_deg=90)
    
def servoGo():
  setup()
  s = SERVO_HTX_900.copy(26)
  s.start()
  
  for i in range (0,s.range_deg):
    s.setDegrees(i)
    time.sleep(0.05)
  
  s.stop()
  GPIO.cleanup()

servoGo()