Amazing Raspberry Pi projects sites

https://www.sparkfun.com/

http://magpiindex.steverigg.co.uk/

http://rpihouse.wordpress.com/feed/

http://www.raspberrypi.org/forums/viewforum.php?f=15

Raspberry Pi - Sh scripts in Python

How to write sh commands in Python

By Importing the library OS in python, we can use the  'sh' scripts in python very easily.

sh script  'a.sh' to echo the 'Hello World'

Python program to use 'a.sh' shell script

Output:

 

Node Server.js in Raspberry Pi

To serve a page using Node.js  require a few lines of code. Raspberry pi browser shows hello world webpage which is running on Node(screenshots below)


Node Server.js program running

 

Raspberry Pi browser shows the page in localhost port 8888




Server.js Program

node.js Hello World Program

Just thought of writing a program in Node.js. There are a lot of tutorials in Node.js.

I am following the link http://www.nodebeginner.org/#javascript-and-nodejs

HelloWord program

use console.log for printing strings.

console.log("Hello World");

Node.js on Raspberry Pi

I am not sure much about Node.js. But like to try something with node.js in Raspberry pi. Here is installation steps for Node.js.

Node.js is a cross-platform runtime environment and a library for running applications written in JavaScript outside the browser (for example, on the server).

Node.js applications are designed to maximize throughput and efficiency, using non-blocking I/O and asynchronous events. Node.js applications run single-threaded, although Node.js uses multiple threads for file and network events.Internally, it uses the Google V8 JavaScript engine to execute code, and a large percentage of the basic modules are written in JavaScript.

Node.js was created by Ryan Dahl starting in 2009. Its development and maintenance is sponsored by Joyent.

Installation Steps for Node.js in Raspberry Pi


1. sudo apt-get upgrade
2. sudo apt-get update

Install Node and NPM

wget http://nodejs.org/dist/v0.10.2/node-v0.10.2-linux-arm-pi.tar.gz
tar -xvzf node-v0.10.2-linux-arm-pi.tar.gz

set the path variable as the bin directory

PATH=$PATH:/home/pi/node-v0.10.2-linux-arm-pi/bin

after the setting the path variable , try the command in command line
npm  - -version

in order to work on native modules , we need to install  node-gyp

check whether gcc is installed or not ?
gcc --version

install Native

npm install -g node-gyp

X,Y coordinates in Joystick in Pygame

Co-ordinates can be controlled easily with pygame joystick get_axis function.

joystick.get_axis(0) returns the 'x' axis position, at the same time
joystick.get_axis(1) returns the y axis position of the joystick. You can add to you rectangle image coordinates with the above values to make movement to the image in X,Y axis.

# get the rectangle the image occupies
# rec(x, y, w, h)
start_rect = image.get_rect()
image_rect = start_rect
.....
.....
.....
hor_x   = joystick.get_axis(0)
hor_y   = joystick.get_axis(1)
image_rect.left = image_rect.left+ hor_x * 2
image_rect.top = image_rect.top+ hor_y * 2

Joystick Axis control with Pygame

Raspberry Pi joystick Pygames

As blogged before the screen image position controlling with joystick button are done. The good thing about electronic devices are that there will be many more things to explore further .Joy stick works as coordinates of the axis when we move it. Looks like its values moves from 1.0 to -1.0 . I am interested to control the screen image with this axis rather than buttons in the joystick.

Looking further on the documentation in Pygame - http://www.pygame.org/docs/ref/joystick.html

get_axis()

get the current position of an axis

get_axis(axis_number) -> float

Returns the current position of a joystick axis. The value will range from -1 to 1 with a value of 0 being centered. You may want to take into account some tolerance to handle jitter, and joystick drift may keep the joystick from centering at 0 or using the full range of position values.

The axis number must be an integer from zero to get_numaxes()-1.

DHT11 connected to Raspberry Pi to measure Room Temperature & Humidity

As always the difficult part while interfacing a device especially sensors is  the signal decoding. I always felt difficult to understand the specifications of a electronic device.

DHT11 decoding code and instructions I got from the below link 

http://www.uugear.com/portfolio/dht11-humidity-temperature-sensor-module/

Raspberry Pi and DHT11 connection Diagram:

I just followed the instructions and finially I measured my room temperature and humidity.

Ordered a DHT11 to connect with Raspberry Pi

Today I have ordered DHT11 in ebay.Just need to do some experiment with GPIO pins on Raspberry Pi in input mode.

DHT11 Temperature and Humidity Sensor features a calibrated digital signal output with the temperature and humidity sensor complex. Its technology ensures the high reliability and excellent long-term stability. A high-performance 8-bit microcontroller is connected. This sensor includes a resistive element and a sense of wet NTC temperature measuring devices. It has excellent quality, fast response, anti-interference ability and high cost performance advantages

DHT11 timing diagram:

DHT11 connection Diagram:

Waiting for it to come.................................

Object Game in Raspberry Pi using Pygame

It is easy to build falling balls in Pygame and try to use the sleep function to delay the balls.

Video in youtube: