Turn on an LED when connected to wifi

[mb02155]

Hello,

I am looking for a script (python?) that when will start when the pi boots up and continually check to see if the wifi has successfully connected to a wifi AP and will turn on a LED (connected to GPIO) indicating connection.

I need this because I will have a pi in a location that will not have a display and is on the edge of the wifi range. I want a quick easy way to confirm that the pi is connected.

Does anyone have any script that will help me accomplish this?

Thanks in advance!

[DougieLawson]

It's not python (will bash do?)

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#!/bin/bash

# ping the gateway address
/bin/ping -q -c1 192.168.1.254 > /dev/null

if [ $? -eq  0 ]
then
  echo "Network active"
  # stuff to do when the network is active goes here ...   

else
  echo "Network down"
  # stuff to do when the network is down goes here ...
fi

You can also add scripts to /etc/network/if-up.d and they will be automatically run when the network connects.

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#!/bin/sh -e
# Called when a new interface comes up
# don't bother doing anything when lo is configured.
if [ "$IFACE" = "lo" ]; then
        exit 0
fi
# stuff to do when the network comes up active goes here ...
exit 0

[iinnovations]

From python you can get wpasupplicant status, which is what I do:

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def getwpaclientstatus():
    import subprocess

    try:
        writedatedlogmsg(networklog, 'Attempting WPA client status read. ', 4, networkloglevel)
        result = subprocess.Popen(['/sbin/wpa_cli', 'status'], stdout=subprocess.PIPE)
    except:
        writedatedlogmsg(networklog, 'Error reading wpa client status. ', 0, networkloglevel)
    else:
        writedatedlogmsg(networklog, 'Completed WPA client status read. ', 4, networkloglevel)


    # prune interface ID
    resultdict = {}

    for result in result.stdout:
        if result.find('=') > 0:
            split = result.split('=')
            resultdict[split[0]] = split[1].strip()
    return resultdict

[mb02155]

Thank you both. I will try both of these!

[Bbuschke]

What pins on the gpio do I connect the led to after the script is set up

[pcmanbob]

What pins on the gpio do I connect the led to after the script is set up

In the above examples no GPIO outputs have been set up, so its down to you to set up your GPIO to work with which ever pins you wish.
here is just one example on how to do that :- https://thepihut.com/blogs/raspberry-pi ... -gpio-pins
there are plenty more out there just google it.

[Bbuschke]

So after this # stuff to do when the network is down goes here ...


I would put in gpio out low?

[pcmanbob]

Hi.

So I wired the LED the same as in the web page example I posted.
I did fined when running Dougie's code that I had to change the IP to 192.168.1.1 my routers gateway or it reported down all the time ?
you may need to change the IP to match your routers gateway.

So this is how the code looks once you add in the GPIO bits

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#!/bin/bash
echo "18" > /sys/class/gpio/export
echo "out" > /sys/class/gpio/gpio18/direction

/bin/ping -q -c1 192.168.1.1 > /dev/null
if [ $? -eq 0 ]
then
	echo "$? network up"
	# Sets pin 18 to high

	echo "1" > /sys/class/gpio/gpio18/value

	
 else
	echo "$? network down" 
	# Sets pin 18 to low

	echo "0" > /sys/class/gpio/gpio18/value 
	
fi

Now there are some things to note
1. you need to run this script as root ( to run at command line use sudo ./name of file )
2. you will get a error message on the second and all following executions " echo: write error: Device or resource busy" because the GPIO pin has already been set up on the previous execution.

now I set this to run every 5 min using cron.
now you have to run as root so use sudo crontab -e to set up cron , assuming you saved the code in a file called cnw.sh in the /home/pi directory and made it executable you just need the line

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*/5 * * * * /home/pi/cnw.sh >/home/pi/log.txt 2>&1

adding to the end of the cron file.
I added the redirect to the log.txt file just so you can check its working once you are happy its working ok you could just change this to

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*/5 * * * * /home/pi/cnw.sh >/dev/null 2>&1

so as to just discard all the output.

If you don't understand any thing or need any other help please ask

[FM81]

May be, you can change this

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echo "18" > /sys/class/gpio/export

to this

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[ -L /sys/class/gpio/gpio18 ] || echo "18" > /sys/class/gpio/export

and you will get no error on second (or third ...) execution.

Greetings, FM_81

[pcmanbob]

May be, you can change this

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echo "18" > /sys/class/gpio/export

to this

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[ -L /sys/class/gpio/gpio18 ] || echo "18" > /sys/class/gpio/export

and you will get no error on second (or third ...) execution.

Greetings, FM_81

Thanks always willing to learn some thing new..

[Bbuschke]

Ok. I think I have the coding down. Now if I find a 3v led but the gpio is sending 3.3v I need a resistor correct? What size resistor?

[rpdom]

Ok. I think I have the coding down. Now if I find a 3v led but the gpio is sending 3.3v I need a resistor correct? What size resistor?

The formula for working out resistors for LEDs is fairly simple. There are even lots of calculators online for it.

You need to know the supply voltage (Vsupply = 3.3V in this case), the LED voltage (Vled = 3.0V) and the LED current in Amps (Iled = ? try 0.01 Amps which should give a reasonable brightness and not be too much for a GPIO).

The formula is: R = (Vsupply - Vled) / Iled

R= (3.3 - 3.0) / 0.01

R= 0.3 / 0.01

R = 30 Ohms

You should be able to get a 33 Ohm resistor fairly easily, that's the next value up from 30.

[pcmanbob]

Ok. I think I have the coding down. Now if I find a 3v led but the gpio is sending 3.3v I need a resistor correct? What size resistor?

No need to find a 3v LED just use a regular LED red,green or yellow which have a forward voltage around 1.5 -2.0v and a 330ohm or 470ohm resistor and it will work just fine.

[Bbuschke]

i got up to the creating the script and im lost at the Cron thing

[Martin Frezman]

i got up to the creating the script and im lost at the Cron thing

This may or may not be the topic that is causing you to get lost, but I think it is bad advice to use "sudo crontab -e".

Instead, just use ordinary "crontab -e", and use "sudo" in the command (so you just put the same string in the crontab line as you would use to run the program from the ordinary shell command line).

[Bbuschke]

Yeah I'm lost. Think I need to find a step by step tutorial. I appreciate the help but I'm very new to all this. I don't have any knowledge in coding and stuff. I don't expect you guys to make a tutorial for me. I will try to research this some more

[pcmanbob]

Yeah I'm lost. Think I need to find a step by step tutorial. I appreciate the help but I'm very new to all this. I don't have any knowledge in coding and stuff. I don't expect you guys to make a tutorial for me. I will try to research this some more

Hi.

If you tell me were you have saved your script and what you have called it I will write you a how to. you just need to run cron as root. if you start putting sudo in your cron entries you will have problems.

[Bbuschke]

Script named wifi_led.py

Located in
/home/pi/scripts/wifi_led.py

I really appreciate the help

[Martin Frezman]

if you start putting sudo in your cron entries you will have problems.

Wrong.

[pcmanbob]

Script named wifi_led.py

Located in
/home/pi/scripts/wifi_led.py

I really appreciate the help

Hi.

Bit confused, the scripts posted here were bash scripts, but you seemed to have saved yours with a python extension.
so just to clarify is your script bash or python script.
and
Does it self loop or does it just run once on each call.
its makes a difference on how we call it in cron.

[Bbuschke]

Saved same place and file name but bash now.
/home/pi/scripts/wifi_led.sh

I just used your script example. I don't know if it self loops
I want it to stay on at all times when Connected to a network

[pcmanbob]

Saved same place and file name but bash now.
/home/pi/scripts/wifi_led.sh

I just used your script example. I don't know if it self loops
I want it to stay on at all times when Connected to a network

Ok no problem.

First off just in case you have not done it. we need to make the script executable, we do this with chmod.
so you need to run this command in a terminal window ( if using raspbian with desktop) or at the command line (if using raspbian lite ).

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chmod +x /home/pi/scripts/wifi_led.sh 

so now we need to create a cron entry.
at the same command line run this command it will open crontab as the root user.

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sudo crontab -e

this will open a temp cron file in nano.
so using the keyboard arrow keys scroll to the first line below the line "# m h dom mon dow command"
now enter this line

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*/3 * * * * /home/pi/scripts/wifi_led.sh >/dev/null 2>&1

now just press and hold the Ctrl key and press o ( thats letter O ) followed by return.
you should get a response telling you how many lines were written.
now just do Ctrl and x if all is well you will get a message saying installing new crontab.
That's it you now have you network status LED script running every 3 min.
now you could make this work every 2 min if you wanted by going through the same procedure to edit the cron entry and just change the 3 to a 2.
now by default this script prints to the screen telling you if the network is up or down as we have this script running in the back ground we don't want this that why we added the redirect on the end of the cron line.

so that's it after 3 mins your LED should be on if your network is connected, it will check your network every 3 min and update the LED.

if you have any problems or questions please come back to me.

[Bbuschke]

i get this when making script excutable
chmod: changing permissions of ‘/home/pi/scripts/wifi_led.sh’: Operation not permitted

[pcmanbob]

i get this when making script excutable
chmod: changing permissions of ‘/home/pi/scripts/wifi_led.sh’: Operation not permitted

how did you create this file did you use nano or sudo nano ?

ok lets see who owns the file then, from a command line
first change to the scripts directory.

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cd scripts

then

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ls -l

and post back the results

[Martin Frezman]

This is precisely why you should drop the sudo in all your "normal"/"terminal" commands. You don't need it (really, seriously, and you can ignore anyone who says you do) and, as you've discovered, it can screw you up (you end up with files owned by root and not writable by pi).

Instead, as I stated above, you should just put the 'sudo' in the crontab file (i.e., as part of the command to run). Then your crontab entry looks just like the command you would use to run the program "manually" (i.e., from the shell/terminal) and everything is as it should be.

And any comments by any other posters to the effect that you can't put "sudo" inside a crontab line - can, as you now know, be ignored.