fn main(): 08/01/2014

Monday, August 11, 2014

Not sure how to record the keys of my TV remote with IRRECORD

As per the google search results I tried recording my TV remote keys to create lirc.conf file. Its creating the conf file, but the 'irw' not detecting the keys .

Not sure anything wrong I am doing while recording the keys in the TV remote.

pi@raspberrypi ~ $ irrecord -d /dev/lirc0 ~/lircd.conf

http://www.lirc.org/html/irrecord.html

Saturday, August 9, 2014

IR transmitter with Raspberry Pi

IR Remote set up with Raspberry Pi

Try to set up IR transamitter with Raspberry Pi!!

IR is one of the low cost communication method we can set up between devices. When started searching for IR transmitter with Raspberry Pi, I came to know that there is a pretty good module LIRC already for IR set up in Raspberry Pi
http://www.lirc.org/

Install LIRC with following command

sudo apt-get install lirc

edit the /etc/modules to add the following lines

lirc_dev
lirc_rpi gpio_in_pin=23 gpio_out_pin=22

Follow the instructions in the link http://tsagi.me/electronics/2013/06/07/universal-raspberry-pi-remote/

To start and stop LIRC

sudo /etc/init.d/lirc stop
sudo /etc/init.d/lirc start

Connection diagram and Device Image

It pretty easy to connect the IR to Raspberry Pi, you need to know the VCC and GND both VCC and Raspberry Pi.

IR Key detection Pulse in Raspberry Pi with LIRC

There are steps where you can map the keys in the remote and make your own IR remote ...... interesting

http://randomtutor.blogspot.in/2013/01/web-based-ir-remote-on-raspberry-pi.html

https://www.cl.cam.ac.uk/projects/raspberrypi/tutorials/robot/cheat_sheet/

http://circuitdesign4u.blogspot.in/2013/02/remote-operated-lighting-system.html

http://tsagi.me/electronics/2013/06/07/universal-raspberry-pi-remote/

Thursday, August 7, 2014

i2c connection in Raspberry Pi

What is i2c ?

I²C (Inter-Integrated Circuit), pronounced I-squared-C, is a multi-master, multi-slave, single-ended, serial computer bus invented by Philips Semiconductor, known today as NXP Semiconductors, used for attaching low-speed peripherals to computer motherboards and embedded systems. Alternatively I²C is spelled I2C (pronounced I-two-C) or IIC (pronounced I-I-C).

I heard about i2c , but never experimented something with i2c connections. Now I have an opportunity to do that with Raspberry pi. Its kind of Master -Slave communication or address to address communication.Advantage of this is , with 2 pins ( SDA,SDL) you can control many pins of a device or IC which having i2c provision.

Raspberry Pi have i2c communication provision:

Raspberry i2c set up procedure:

To use the I²C module with the Raspberry Pi, follow the below steps

1.Enable the I²C driver on the Pi by typing sudo vi /etc/modprobe.d/raspi-blacklist.conf

comment the line blacklist i2c-bcm2708 with an #
and save the file

2.Edit the modules file with the command sudo vi /etc/modules and add "i2c-dev" to a new line, then save the file

3.Install the i2c-tools package: sudo apt-get install i2c-tools.

4.Install the python 'smbus' module: sudo apt-get install python-smbus.

5.reboot raspberry pi

6.After the reboot, test to see if there is a device connected with the command i2cdetect -y 0

Activate the I²C device with sudo modprobe i2c-dev. This must be done whenever the Pi is restarted.

Reference :

https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c

http://en.wikipedia.org/wiki/I%C2%B2C

http://www.robot-electronics.co.uk/htm/raspberry_pi_examples.htm

https://www.cl.cam.ac.uk/projects/raspberrypi/tutorials/turing-machine/two.html

Tuesday, August 5, 2014

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:

Monday, August 4, 2014

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

Sunday, August 3, 2014

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.

Saturday, August 2, 2014

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: