Raspberry Pi Blog

Running Pi headless - SSH tunneling part2

In this tutorial, I will demonstrate the following:-

1. Login through ssh
2. Changing pi's password
3. Navigating through file-system
4. Copying files on network
5. Shutdown, Reboot pi
6. Writing, compiling a C program

Download Notes

Running Pi headless - SSH tunneling part1

Pi normally needs hardware support like keyboard, mouse, display( HDMI compatible monitors). But we can run pi without these hardware too, using another PC by SSH tunneling. Before getting started, we need to install ssh client in the system from which we are tunneling in to the pi. In Ubuntu (or other linux distros), we install ssh client as follows:

$ sudo apt-get install ssh
$ sudo apt-get install openssh-client

Default login for pi running Wheezy:

usrname: pi
passwd: raspberry

Follow the video below which explains what is SSH and how to log in to pi by SSH tunneling step by step:

Dowload notes/hints

difference between arduino and raspberry pi

Ever since the Raspberry Pi was announced, it has been a topic of much debate online.Starting from profoundly diverse naming plans- masculine Italian name vs sweet fruit pie- Arduino and Raspberry Pi boards are significantly different in a lot of things. For one Arduino is an Open Source single-board micro-controller, while Raspberry Pi is a single-board computer.

Ask any electronics enthusiastic and he will tell you why it is preferable to get the Arduino if this is your first time venturing into the world of embedded systems.On the other hand, if you have already dipped your toes in this field you could go ahead with the Raspberry Pi.

The table compares the two boards. It should help you make a good decision if you are new to this field.

Arduino	Raspberry Pi
Extremely simple to get working.	Less simpler to get working.
A typical embedded system with easy-to-develop software.	Fully fledged computer running Linux.
Support is available virtually everywhere.	Limited support is available at present but should increase over time.
Perfect for controlling hardware(robotics).	Features an extremely powerful GPU and can handle HD content.
Umpteen, different kits and shield’s are available.	Very few kits are available presently.
Low power consumption(<0.5 W), capable of even running micro amps with very low clock.	Power consumption(~3.5 W) is comparatively higher than Arduino.

Verdict: While the Raspberry Pi is a great high-performance option, Arduino is a good general-purpose board.

Using GPIO on Raspberry Pi to blink an LED

One of the few things that separates the Pi from other SBC (Single Board Computer) is the ability to use the GPIO (General Purpose Input/Output) pins which can be set as HIGH or LOW to control any external devices. All you need is a female to male jumper wire to get started. Here I have used a HDD IDE connector to get the job done.

In this post pin 9 is used for GND and pin 11 for GPIO17. The LED was connected using a 470 ohm register in series with pin 9 and 11 to limit the current.

Software Implementation:-

The fastest way to get started is to use python which comes pre-installed with all images. Download the RPi.GPIO library and copy the gz tar ball to the RPi wheezy raspbian. Open the terminal and navigate to the extracted folder containing the RPi.GPIO library. Then type: $ sudo python setup.py install to install the module. Imp: As the OS is multitasking and not Real-time unlike Arduino there may be jitters depending on CPU priority.

Based on the library I have written a simple code to turn ON and turn OFF the LED after a delay of 1 sec (1000ms) each.The LED blinks 50 times.

import RPi.GPIO as GPIO
import time
# blinking function
def blink(pin):
        GPIO.output(pin,GPIO.HIGH)
        time.sleep(1)
        GPIO.output(pin,GPIO.LOW)
        time.sleep(1)
        return
# to use Raspberry Pi board pin numbers
GPIO.setmode(GPIO.BOARD)
# set up GPIO output channel
GPIO.setup(11, GPIO.OUT)
# blink GPIO17 50 times
for i in range(0,50):
        blink(11)
GPIO.cleanup()

Bluetooth pairing on Raspberry Pi with smartphone

Follow the steps below to pair your Raspberry Pi with your smartphone:-

1. Load a new wheezy raspbian image on SD card via the MAC, from a terminal window enter:
sudo umount /dev/disk1s1
sudo dd bs=1m if=2012-09-18-wheezy-raspbian.img of=/dev/rdisk1
sudo umount /dev/disk1s1
2. Boot Raspbian, perform the initial configuration and increase the size of SD to maximum (4GB), & Reboot.
3. Perform a ssh login to Raspbian from MAC, username pi pw raspberry and enter commands:
su
(enter root password)
apt-get update
apt-get install -y bluetooth bluez-utils blueman
lsusb
/etc/init.d/bluetooth status
4. Enable tightvncserver and remote connect to Raspbian to see its GUI.
5. From Raspbian's GUI select Preferences->Bluetooth Manager, a Bluetooth Devices window will pop up.
Click 'Search' on the Bluetooth Devices, go to the phone, turn on Bluetooth and enable discovery.
6. When Raspberry Pi detects the smartphone, click + on the Bluetooth Devices window. Click Setup, specify password 0000 on the Bluetooth Assistant window.
7. On the smartphone, enter 0000 to pair with Raspberry Pi, the phone should display "raspberry3-14" as a paired device.

The Raspberry Pi Bluetooth name can be changed using : Adapter->Preferences and change the Friendly Name.

Setting up webcam on Raspberry Pi

I wanted to find out if the Raspberry Pi supports webcam or not. So I pulled an old Microsoft LifeCam NX-3000 to test with the Pi.The packages were talking a long time to load so I had to perform most of my installation on the emulator instead.
Since my MAC has single hard disk drive, the USB drive for the SD card would always be on /dev/disk1s1 when plugged in. To overcome the problem I created a shell script to write any Raspberry Pi images on the SD card.

#!/bin/bash
sudo diskutil umount /dev/disk1s1
sudo dd bs=1m if=$1 of=/dev/rdisk1
sudo diskutil umount /dev/disk1s1

Through Qemu you can quickly install debian packages on SD card.The image can be loaded on the SD card using the script above.Follow the steps below to test webcam packages on the Raspberry Pi:

1. Remotely access your Linux box using ssh, then mount the folder containing wheezy raspbian image.
2. Create a raw 3GB raw image disk and copy wheezy raspbian onto it:
qemu-img info 2012-09-18-wheezy-raspbian.img
qemu-img create -f raw newwheezy.img 3G
dd if=2012-09-18-wheezy-raspbian.img of=newwheezy.img
3. Start qemu without graphic, and specify 512MB memory (or replace the flag to -m 1024 to use 1GB memory), command:
sudo qemu-system-arm -kernel kernel-qemu -cpu arm1176 -M versatilepb -m 512 -no-reboot -append "root=/dev/sda2" -hda newwheezy.img -net nic -net user -nographic
4. Within qemu emulating Raspbian:
sudo passwd root
(enter new root password: root, twice)
su
(enter root)
aptitude update
aptitude install -y camorama
aptitude show camorama (to make sure it's installed).
shutdown -h now
(enter Ctrl-a x to exit qemu, then quit ssh session to go back to the MAC).
5. From the MAC, use sftp or scp to copy the new wheezy raspbian image loaded with camorama, command:
./loadsd.sh newwheezy.img
6. Now boot your Raspberry Pi with new wheezy raspbian. Enter command: startx to start the GUI & click LXTerminal, enter:
lsub (a list of USB devices is displayed, one of those lines listed the LifeCam)
camorama (command to start camorama, or command cheese to start cheese)