CODEWITHSUNDEEP
pythonclinuxarduinoraspberry-pi
OakRidgejet
OakRidgejet

Reputation: 55

Arduino, Raspberry Pi, and HTML page

Currently I have an Arduino hooked up to a Raspberry Pi. The Arduino controls a water level detection circuit in service to an automatic pet water bowl. The program on the Arduino has several "serial.println()" statements to update the user on the status of the water bowl, filling or full. I have the Arduino connected to the Raspberry Pi via USB. The small python program on the Pi that captures the serial data from the Arduino is as follows:

import serial

ser = serial.Serial('/dev/ttyUSB0',9600)
file = open('index.html', 'a+')
message1 = """<html>
<head><meta http-equiv="refresh" content="1"/></head>
<body><p>"""
message2 = """</p></body>
</html>"""

while 1:
        line=ser.readline()
        messagefinal1 = message1 + line + message2
        print(line)
        file.write(messagefinal1)
        file.close()

As you can see it captures the serial data coming over USB, creates and html page, and inserts the data into the page. I am using a service called "dataplicity" (https://www.dataplicity.com), more specifically their "Wormhole" tool (https://docs.dataplicity.com/docs/host-a-website-from-your-pi), to view that html file over the web at a link that the wormhole tool generates. The problem I am having is this:

Traceback (most recent call last):
  File "commprog.py", line 15, in <module>
    file.write(messagefinal1)
ValueError: I/O operation on closed file

I want to continuously update the html page with the status of the water bowl (it is constantly printing its status). However once I close the page using "file.close()" I can't access it again, presumably because the wormhole service is accessing it. If I don't include .close() I have to end the process manually using ctrl c. Is there a way I can continuously update the html file?

Upvotes: 0

Views: 319

Answers (2)

radoslav-from-dataplicity.io
radoslav-from-dataplicity.io

Reputation: 31

If you want to continuously update your webpage you have couple of options. I don't know how you serve your page but you might want to look at using Flask web framework for python and think about using templating language such as jinja2. A templating language will let you create variables in your html files that can be updated straight from python script. This is useful if you want the user to see new data on your page each time after they refresh it or perform some operation on the page.

Alternatively you might want to think about using websockets similarly as in the example I made here . Websockets are useful if you want your user to see new updates on your page in real time.

I appreciate the fact that the above answer doesn't answer your question directly but what I'm offering here is a clean and easy to maintain solution once you set it up.

Upvotes: 1

A. Entuluva
A. Entuluva

Reputation: 729

After the first iteration of your while loop, you close the file and never open it again for editing. When you try to append to a file that is closed, you get an error. You could instead move the open statement inside your loop like so:

while 1:
    line=ser.readline()
    messagefinal1 = message1 + line + message2
    print(line)
    file = open('index.html', 'a+')
    file.write(messagefinal1)
    file.close()

Upvotes: 2

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