zefanja/aqi

Json and other errors when running your code

Closed this issue · 6 comments

Blkprometheus commented

I'm using your code based on the instructions in this article, "https://openschoolsolutions.org/measure-particulate-matter-with-a-raspberry-pi/". I'm using a Raspberry PI 3 running Raspbian Stretch Lite and Python 2.7.x. with this sensor, Particulates sensor SDS011. When I run aqi.py from the command prompt, after about a minute of running I get this error,
"pi@raspberrypi:~ $ ./aqi.py
PM2.5: 227.6 , PM10: 261.4
PM2.5: 228.1 , PM10: 260.1
PM2.5: 230.4 , PM10: 262.4
PM2.5: 228.5 , PM10: 259.2
PM2.5: 230.1 , PM10: 259.6
PM2.5: 231.4 , PM10: 260.8
PM2.5: 232.9 , PM10: 261.9
PM2.5: 233.3 , PM10: 262.3
PM2.5: 232.4 , PM10: 261.4
PM2.5: 231.4 , PM10: 259.9
PM2.5: 228.6 , PM10: 256.8
PM2.5: 226.2 , PM10: 254.3
PM2.5: 225.5 , PM10: 253.9
PM2.5: 224.4 , PM10: 252.3
PM2.5: 225.4 , PM10: 253.2
Traceback (most recent call last):
File "./aqi.py", line 110, in
data = json.load(json_data)
File "/usr/lib/python2.7/json/init.py", line 291, in load
**kw)
File "/usr/lib/python2.7/json/init.py", line 339, in loads
return _default_decoder.decode(s)
File "/usr/lib/python2.7/json/decoder.py", line 364, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/usr/lib/python2.7/json/decoder.py", line 382, in raw_decode
raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded".

When I access the Raspberry Pi from a browser, at first I see the AQI (PM2.5) and AQI (PM10) boxes at the top of the page, but nothing else. After a few minutes these messages are displayed on the website, --2018-10-08 02:21:34-- https://raw.githubusercontent.com/zenfanja/aqi/master/html/index.h Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 151.101.0.133, 151.101.64.133, 151.101.128.133, ... Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|151.101.0.133|:443... connected. HTTP request sent, awaiting response... 404 Not Found 2018-10-08 02:21:34 ERROR 404: Not Found.

Any ideas on how I can resolve these issues?

Thanks,

David Lynum

jimbob666 commented

Hey David - Where are you in the world with PM number so high? Mine are normally under 30 and under 10 in most cases.

wallarug commented

Hey @Blkprometheus (David),

I am not sure what your exact issue is, however, the tutorial did contain a small error that I thought I would let you know about.

Solution One

The tutorial instructions have a small error on them where the directory for your HTML file has an extra "w". The instructions should read:

Section: Reading data on the Raspberry Pi

$ sudo chown pi:pi /var/www/html/
$ echo[] > /var/www/html/aqi.json

Section: HTML page for display of measured values and AQI

$ wget -O /var/www/html/index.html https://raw.githubusercontent.com/zefanja/aqi/master/html/index.html
$ wget -O /var/www/html/aqi.js https://raw.githubusercontent.com/zefanja/aqi/master/html/aqi.js
$ wget -O /var/www/html/style.css https://raw.githubusercontent.com/zefanja/aqi/master/html/style.css

There is a potential that you may have an issue relating to the above incorrect directory. It sounds like that instead of downloading the file correctly, you have instead copied the error into the HTML file.

Solution Two

Another possibility is that you have not set the correct permissions on the files. I would highly recommend that you issue the below command on all the files to ensure that the aqi.py program is able to access them all.

$ chmod +x aqi.py
$ chmod 755 /var/www/html/aqi.json
$ chmod 755 /var/www/html/aqi.hml

...and any other files associated with the project.

Let us know how you go.

I am also interested in what City you are in. You're numbers are absolutely crazy high! as pointed out by @jimbob666

ahabandfedallah commented

I had this issue as well, and I realized it was because I entered the ECHO command incorrectly.

The instructions should read (note the space between echo and the square brackets)

echo [] > /var/www/html/aqi.json

Not placing the space will render an error with the echo command. Removing the brackets will not give you the correct thing to echo.

Blkprometheus commented
zefanja commented

@Blkprometheus Could you resolve your problem?

Blkprometheus commented

Yes, I used both solutions, just in case, and my problem was resolved. Thank you for your help.