raspi_blinky

Blink an LED from your browser two different ways

What is this About?

This code is designed to show three different ways to control an LED attached to a Raspberry Pi from a remote browser. Two are with cgi-bin and a web server, and one is with a stand-alone python daemon using the Cherry Py web framework.

Prerequisites

This project uses the current stock Python on Raspian Stretch (9.0), which as of this writing is 2.7.13.

I used 2017-11-29-Raspbian_stretch_lite for this project, directly from the Raspbian downloads page. I assume an already set up Raspberry Pi. You will need to install the lighttpd package: apt-get install lightttpd

You will also need Cherry Py 14.0.0 or better. The version in the Stretch repository is seriously out of date, so I downloaded it from cherrypy.org and installed from source. Fortunately it is all-python, so installation is not too hirsute. I experimented with the python pip installer but was not able to make this work.

Making Stuff Work

From lightttpd

Install everything in the mirrored directories (e.g. stuff in ./etc goes to /etc). I assume that you have your LED connected to pin 11 of your RasPi. Out of the box, you'll have to allow www-data to connect to the GPIO pins:

sudo set_gpio_pins -p 11 -u www-data -g www-data

After executing this command, connecting to the root on your Raspi should allow you to turn the LED on and off, but not blink it. To blink the LED from the web server, turn on the blinker daemon in /var/ledDaemon:

cd /var/ledDaemon
./ledDaemon start

You should be able to go to http:<yourmachine>/daemon_index.html to get the option to blink the LED.

You can edit /etc/rc.local to force the appropriate commands to execute on every boot.

From cherry py

Make sure that lighttpd is turned off. Then execute:

cd /var/cherrypy_led
./cherrypyLedDaemon start

Connecting to your machine should then give you a web page where you can blink, turn on, or turn off the LED

Where to change the LED Pin

If your LED is not connected to pin 11 of your raspberry pi, you can change these lines to the correct pin number:

For the CGI on-off page:

vi /var/www/html/index.html
<input type=hidden name="pin" value="11">

For the Daemon on-off-blink page:

vi /var/ledDaemon/ledDaemon.cfg
pinNumber=11

For the cherrypy on-off-blink page:

vi /var/cherrypy_led/cherrypy_led_daemon.py
self.the_led=ledBlinker.ledBlinker(11)

And of course you'll need to change the -p argument to set_gpio_pins.sh:

vi /etc/rc.local
sudo /usr/local/bin/set_gpio_pins.sh -p 11 -u www-data -g www-data