I am trying to control the angle of a servo motor via an Android app that I built, installed on my phone. My phone sends the angle data (i.e. -90 to +90 degrees) to the raspberry pi via a TCP socket. I have identified my desired duty cycles i.e. 50 to 80. Using linear graph theory I derived an equation which takes angle as input and gives the desired duty cycle.
The problem I am facing is that the servo turns on one side and stays there. Although the print statement in th while loop shows that the DutyCycle variable is changing as I rotate my mobile. I have even tried to add a little time delay in the loop, still the problem persists
The code below demonstrates my methodology:
import RPi.GPIO as GPIO
import socket
import os
import re
#----------------------------------------------------------
## TODO: Port network information on background thread.
class CarController:
"""
@param port: port for connectivity
"""
def __init__(self,port):
## Intialize parameters of communication.
self.command= os.popen('ifconfig wlp6s0 | grep "inet\ addr" | cut -d: -f2 | cut -d" " -f1') #Works for WiFi only.
self.TCP_IP = self.command.read()[0:-1]
self.TCP_PORT = port
self.BUFFER_SIZE = 8
self.pattern = re.compile('-*[0-9]+\|[0-9]+$')
##Intialize the connection
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.sock.bind((self.TCP_IP, self.TCP_PORT))
self.sock.listen(True)
print 'Connect to: %s:%d'%(self.TCP_IP,self.TCP_PORT)
#Blocking call.
self.conn, self.addr = self.sock.accept()
print 'Connected with: ',self.addr
"""
@param
@return speed,angle
"""
def getParameters(self):
data = self.conn.recv(self.BUFFER_SIZE)
if(data == 'stop\n'):
self.conn.close()
return -1,-1
if(self.pattern.match(data) != None):
angle,speed=data.split('|')
return int(angle),int(speed);
else:
print 'Frame dropped'
return self.getParameters()
controller = CarController(14002)
speed,angle,dc = 0,0,0
#print "The angle is: %d and speed is: %d"%(angle,speed)
#----------------------------------------------------------
#----------------For driving the car-----------------------
GPIO.setmode(GPIO.BOARD)
GPIO.setup(13,GPIO.OUT)
servo= GPIO.PWM(13,50)
servo.start(65)
while 1:
angle,speed = controller.getParameters()
dc=((angle/2)+65)
servo.ChangeDutyCycle(dc)
print "The angle is: %d ,speed is: %d and DutyCycle: %d"%(angle,speed,dc)
