Raspberry Pi (RPi)¶

Where to buy?¶

I always buy mine from Adafruit, they have tons of other great stuff at great prices. They also make make lots of example code and drivers available for their products.

Install¶

Raspbian is a Raspberry optimized version of Debian. The version installed here is based on Debian Wheezy.

[kevin@raspberrypi ~]$ lscpu
Architecture:          armv6l
Byte Order:            Little Endian
CPU(s):                1
On-line CPU(s) list:   0
Thread(s) per core:    1
Core(s) per socket:    1
Socket(s):             1

Note this output doesn’t really tell you much other than it is ARMv6.

Copying an image to the SD Card in Mac OS X¶

These commands and actions need to be performed from an account that has administrator privileges.

Download the image from a mirror or torrent.
Verify if the the hash key is the same (optional), in the terminal run:
```
shasum ~/Downloads/debian6-19-04-2012.zip
```

Extract the image:

unzip ~/Downloads/debian6-19-04-2012.zip

Attach the SD Card to the computer and identify the mount point:
```
df -h
```
Record the device name of the filesystem’s partition, e.g. /dev/disk3s1
Unmount the partition so that you will be allowed to overwrite the disk, note that unmount is NOT the same as eject:
```
sudo diskutil unmount /dev/disk3s1
```
Using the device name of the partition work out the raw device name for the entire disk, by omitting the final “s1” and replacing “disk” with “rdisk” (this is very important: you will lose all data on the hard drive on your computer if you get the wrong device name). Make sure the device name is the name of the whole SD card as described above, not just a partition of it (for example, rdisk3, not rdisk3s1. Similarly you might have another SD drive name/number like disk2 or disk4, etc. – recheck by using the df -h command both before & after you insert your SD card reader into your Mac if you have any doubts!): e.g. /dev/disk3s1 => /dev/disk3

Note: Using rdisk3 might be faster than using disk3, need to look into this.
Write the image to the card with this command, using the raw disk device name from above (read carefully the above step, to be sure you use the correct rdisk# here!):
```
sudo dd bs=1m if=~/rasbian.img of=/dev/rdisk3
```
If the above command report an error(dd: bs: illegal numeric value), please change bs=1M to bs=1m.

Note that dd will not feedback any information until there is an error or it is finished, information will show and disk will re-mount when complete. However if you are curious as to the progresss - ctrl-T (SIGINFO, the status argument of your tty) will display some en-route statistics.
After the dd command finishes, eject the card:
```
sudo diskutil eject /dev/disk3
```
Insert it in the raspberry pi, and have fun

Configuration¶

Once you download and install Raspbian you have to configure it for it to be useful.

sudo raspi-config and change
1. update raspi-config via the advanced option, update
2. hostname
3. memory split between GPU and RAM
4. resize the file system to the size of your disk
5. set correct timezone via the internationalization option
6. turn on I2C interface
sudo apt-get update and then sudo apt-get upgrade
sudo apt-get install apt-show-versions
sudo easy_install pip then sudo pip install -U pip to get the latest pip version
sudo apt-get install rpi-update and then sudo rpi-update to update the kernel
Fix the pip paths so you don’t have to use sudo (that is a security risk)
1. sudo chown -R pi /usr/local
2. sudo chown -R pi /usr/lib/python2.7/dist-packages
3. sudo chown -R pi /usr/share/pyshare
Fix the pip certificate warnings
1. sudo apt-get install python-dev libffi-dev
2. pip install -U urllib3 certifi pyopenssl
Find outdated python libraries with pip list --outdated then update them with pip install -U package_name

SSH Login¶

To increase security, you can disable password logins and rely on ssh public keys. To do this, take a look here for details. Basic steps are:

Generate an ssh key pair using either RSA (2048-4096 bit) or DSA (1024 bit) both public and private keys. They will be stored in ~/.ssh with the public key having .pub appended to the end:
```
ssh-keygen -C "$(whoami)@$(hostname)-$(date -I)"
```
Note you can create a key for a different username if you change $(whoami) to the user name you want.
Copy the public key (.pub) to the server you will connect to:
```
ssh-copy-id username@remote-server.org
```
This should update ~/.ssh/authorized_keys in the process. Also ensure the correct protections are on the file by:
```
chmod 600 ~/.ssh/authorized_keys
```

Edit /etc/ssh/sshd_config to disable password logins.

PasswordAuthentication no
ChallengeResponseAuthentication no

OSX¶

On OSX install ssh-copy-id via brew and in a terminal window on OSX:

ssh-copy-id pi@raspberry.local

Sound¶

Double check sound works:

aplay /usr/share/sounds/alsa/Front_Center.wav

/boot/config.txt¶

You can change the Pi’s default settings for CPU MHz and memory split (between RAM and GPU) using raspi-config. An alternate way is to simply edit the /boot/config.txt.

[kevin@raspberrypi ~]$ more /proc/cpuinfo
Processor   : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS    : 795.44
Features    : swp half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part    : 0xb76
CPU revision    : 7

Hardware    : BCM2708
Revision    : 0002
Serial      : 000000008e0a5a17

[kevin@raspberrypi ~]$ free -h
             total       used       free     shared    buffers     cached
Mem:          232M        57M       174M         0B        11M        28M
-/+ buffers/cache:        18M       214M
Swap:          99M         0B        99M

The output here shows overclocked to 800 MHz and the GPU given only 16 MB of RAM. Now the CPU MHz will change dynamically based on load. So with no load, my 800 MHz system will default to the original 700 MHz system. If you want to always be running at max speed, put force_turbo=1 in the /boot/config.txt:

[kevin@raspberrypi ~]$ more /boot/config.txt
#uncomment to overclock the arm. 700 MHz is the default.
arm_freq=800

# for more options see http://elinux.org/RPi_config.txt
gpu_mem=16     # can be 16, 64, 128 or 256
core_freq=250
sdram_freq=400
over_voltage=0
force_turbo=1

More info can be found here.