Express Socket PI

Unplug-in the power of pi first when changing circuit!!!

This is the start template for using raspberry pi as a node server, which can let user use the webpage as a interface to communicate with server via socket.io.

How to run the sample server

Power on raspberry PI
After about 20 seconds, open the terminal in you computer, connect to pi using ssh, the user name is pi and the ip address should be 10.0.1.13. The password is qwe.

ssh pi@10.0.1.13

Once you logged into PI, go to directory ~/projects

cd ~/projects

Now get the start template from Github.

git clone git@github.com:haochuan/Express-Socket-PI.git

Now go to the directory of the start template, and install all node modules which would take a long time. The password for using sudo is as same as the login password from ssh.

cd Express-Socket-PI
sudo npm install

When the installation completed, you can now run the server

node server.js

Now open 10.0.1.13:8000 in your favorite browser and to see if you can use the webpage to control the brightness of the lights.
If you want to stop the server, press ctrl + c.
If you want to log out from PI and go back to your computer, press ctrl + d.

Some useful bash command:

ls : list files and directories

cd: change directory

mkdir: create a new directory

cp: copy files or directories

mv: move (rename) files or directories

rm : remove files or directories

For more information, google or see how-to-use-basic-unix-commands-to-work-in-terminal

How to edit code on your computer and then put your local code to PI

Suppose that you would like to put the code in your Desktop, open terminal. IF you have any isuess to get the code from Github, go through how to add ssh key on your computer then have a try again.

cd ~/Desktop
git clone git@github.com:haochuan/Express-Socket-PI.git

When you finish editing, use scp to copy your code into PI

cd ~/Desktop
scp -r Express-Socket-PI pi@10.0.1.13:~/projects/.

Now log into PI, you can find your code in ~/projects/Express-Socket-PI

Note on how to use socket.io to write/read data between webpage and node server

The most important files are ./server.js and ./public/js/script.js. These two files are well documented, go and read through those.

For front end:

$('#red').on('change.fndtn.slider', function(){
    socket.emit('red', { val: $('#red').attr('data-slider') });
});

When the slider with id red changes, use socket.emit to emit the data (second parameter) to the red event (first parameter). The data being sent is a javascript object (for example suppose the val of the slider ($('#red').attr('data-slider')) is 100 here:

{var: 100}

For back end:

socket.on('red', function (data) {
    console.log(data.val);
    piblaster.setPwm(22, Number(data.val) / 100);
});

Let socket listen to event red. When front end sends a data to event red, the callback funcion will excute. So the data in the callback function should be {var: 100}. And data.val should be 100.

The function below is what we use to write data into a specific pin in PI. The first parameter is the pin number on PI, and the second is the value you want to write, which should be from 0 to 1.

piblaster.setPwm(pin_number, value);

pengzyk / Express-Socket-PI