树莓派wifi视频小车（安卓app控制：socket与树莓派通信,surfaceview读取视频流）

树莓派wifi视频小车（安卓app控制：socket与树莓派通信,surfaceview读取视频流）

1.树莓派

树莓派作为服务端，代码如下:

#coding=utf-8
import socket
import time
import sys
import thread
import os
import RPi.GPIO as GPIO
HOST_IP = "172.28.11.3"    
HOST_PORT = 7654        
GPIO.setwarnings(False)  #Echo G21(input)  #trig G20                    
GPIO.setmode(GPIO.BCM)
GPIO.setup(22,GPIO.OUT)
GPIO.setup(27,GPIO.OUT)
GPIO.setup(25,GPIO.OUT)
GPIO.setup(24,GPIO.OUT)
GPIO.setup(18,GPIO.OUT) 
GPIO.setup(23,GPIO.OUT)
GPIO.setup(20,GPIO.OUT)
GPIO.setup(21,GPIO.IN)
pwma=GPIO.PWM(18,100)
pwmb=GPIO.PWM(23,100)
pwma.start(100)
pwmb.start(100)     
print("Starting socket: TCP...")
socket_tcp = socket.socket(socket.AF_INET, socket.SOCK_STREAM)    
print("TCP server listen @ %s:%d!" %(HOST_IP, HOST_PORT) )
host_addr = (HOST_IP, HOST_PORT)
socket_tcp.bind(host_addr)   
socket_tcp.listen(1)  
def checkdist():
	while True:
		GPIO.output(20,True)
		time.sleep(0.000015)
		GPIO.output(20,False)
		while not GPIO.input(21):
			pass
		t1=time.time()
		while GPIO.input(21):
			pass
		t2=time.time()
		socket_con.send("distance:"+str((t2-t1)*340/2)+'m')
		#print(1)
		time.sleep(0.3) 
def camera():
	os.system('cd ~/mjpg-streamer/mjpg-streamer-experimental && ./mjpg_streamer -i "./input_uvc.so" -o "./output_http.so -w ./www"')
thread.start_new_thread(camera,())   
while True:
	pwma.ChangeDutyCycle(50)
	GPIO.output(22,0)
	GPIO.output(27,0)
	pwmb.ChangeDutyCycle(50)
	GPIO.output(25,0)
	GPIO.output(24,0)  
    print ('waiting for connection...')
    socket_con, (client_ip, client_port) = socket_tcp.accept()    
    print("Connection accepted from %s." %client_ip)
	thread.start_new_thread(checkdist,())  
	# socket_con.send("Welcome to RPi TCP server!")   
	while True:
		data=socket_con.recv(1024)   
                #if data:    
                        #print(data)
                        #socket_con.send(data)
		if data=='a':     
			#socket_con.send(data)                                   #forward
			pwma.ChangeDutyCycle(50)
			GPIO.output(22,True)
			GPIO.output(27,False)
			pwmb.ChangeDutyCycle(50)
			GPIO.output(25,True)
			GPIO.output(24,False)    
		elif data=='b':                                         #back
			pwma.ChangeDutyCycle(50)
			GPIO.output(22,0)
			GPIO.output(27,1)
			pwmb.ChangeDutyCycle(50)
			GPIO.output(25,0)
			GPIO.output(24,1)  
               	elif data=='d':                                 #left
			pwma.ChangeDutyCycle(50)
			GPIO.output(22,1)
			GPIO.output(27,0)
			pwmb.ChangeDutyCycle(50)
			GPIO.output(25,0)
			GPIO.output(24,1)  
		elif data=='c':		#right
			pwma.ChangeDutyCycle(50)
			GPIO.output(22,0)
			GPIO.output(27,1)
			pwmb.ChangeDutyCycle(50)
			GPIO.output(25,1)
			GPIO.output(24,0)  
		else:
			pwma.ChangeDutyCycle(50)
			GPIO.output(22,0)
			GPIO.output(27,0)
			pwmb.ChangeDutyCycle(50)
			GPIO.output(25,0)
			GPIO.output(24,0)  


socket_tcp.close()
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其中HOST_IP为树莓派的ip，也就是socket服务端的ip，HOST_PORT可以自行设置，但是服务端和客户端必须保持一致。其中开启了2个线程，一个是用于开启mjpg-streamer的命令，一个是用于超声波的采集，传输到安卓端（客户端）。为了视频传输，树莓派必须安装mjpg-streamer。

2.安卓

作为客户端连接树莓派，surfaceview读取mjp-streamer视频流，按键控制小车移动，并显示超声波数据。附件为app工程。