Run Python scripts from JavaScript functions

问题

We need to run a Python code which will control the GPIO of Raspberry Pi 3 from within the JavaScript. (JavaScript is listening for changes on database and when changes are made, function gets triggered and it should run the Python Code.

(This code is not working, like the alert message will pop-up but the python code isn't running which otherwise should turn the LED on. What am i doing wrong?)

index.html file

function runPython()
{
    $.ajax({
    type: "POST", 
    url: "/home/pi/Desktop/Web/led.py",
    data :{},
    success: callbackFunc
    });
}

function callbackFunc(response)
{
    alert("working");
}

led.py file

import RPi.GPIO as GPIO
import timemGPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(18, GPIO.OUT)
print "LED on"
GPIO.output(18, GPIO.HIGH)
time.sleep(10)
print "LED off"
GPIO.output(18,GPIO.LOW)

回答1:

You code is not working because you can't access and run script on server directly from a browser, you can only pass the data to the server using ajax, therefore the url in the ajax should be the server url, and you have to send the data.

On your server (i.e. your Raspberry Pi), you need to have a http(web) server. The server will handle the post request coming from your javascript and control the GPIO accordingly. Like other mentioned, you can use Flask web development framework to create a web server for handling the request(s), or alternatively I often uses http.server which is part of python standard library to create my own GET and POST request handlers for simple applications like this one.

Here is an approach of using http.server where do_GET method create a web page and run the javascript when pointing the browser to the server/RPi IP/URL, and 'do_POST' method handle the post data sent by the ajax to control the GPIO.

web_gpio.py (in Python 3 syntax)

import time
import RPi.GPIO as GPIO
from http.server import BaseHTTPRequestHandler, HTTPServer


host_name = '192.168.0.115'    # Change this to your Raspberry Pi IP address
host_port = 8000


class MyHandler(BaseHTTPRequestHandler):
    """ 
    A special implementation of BaseHTTPRequestHander for reading data 
    from and control GPIO of a Raspberry Pi
    """

    def do_HEAD(self):
        self.send_response(200)
        self.send_header('Content-type', 'text/html')
        self.end_headers()

    def _redirect(self, path):
        self.send_response(303)
        self.send_header('Content-type', 'text/html')
        self.send_header('Location', path)
        self.end_headers()

    def do_GET(self):
        html = '''
        <html>
        <body>
        <p>this webpage turn on and then turn off LED after 2 seconds</p>
        <script src="http://code.jquery.com/jquery-1.12.4.min.js"></script>
        <script>
          function setLED()
            {{
              $.ajax({
              type: "POST",
              url: "http://%s:%s",
              data :"on",
              success: function(response) {
                alert("LED triggered")
              }
            });
          }}
          setLED();
        </script>
        </body>
        </html>
        '''
        self.do_HEAD()
        html=html % (self.server.server_name, self.server.server_port)
        self.wfile.write(html.encode("utf-8"))

    def do_POST(self):
        # Get the post data
        content_length = int(self.headers['Content-Length'])
        post_data = self.rfile.read(content_length).decode("utf-8")
        if post_data == "on":
            GPIO.setmode(GPIO.BCM)
            GPIO.setwarnings(False)
            GPIO.setup(18, GPIO.OUT)
            GPIO.output(18, GPIO.HIGH)
            time.sleep(2)
            GPIO.output(18, GPIO.LOW)
        self._redirect('/')


if __name__ == '__main__':

    http_server = HTTPServer((host_name, host_port), MyHandler)
    print("Running server on %s:%s" % (host_name, host_port))
    http_server.serve_forever()

Run the python script on the server:

python3 web_gpio.py

Either launch your browser and point the browser to the server/RPi ip (in my example, it is 192.168.0.115:8000) or run curl command form another terminal session to simulate the GET request.

curl http://192.168.0.115:8000

Hope this example would give you the idea on how to control something on your server using a simple web server.

来源：https://stackoverflow.com/questions/49934730/run-python-scripts-from-javascript-functions

标签

javascript

python

raspberry-pi

gpio