Raspberry Pi How to

Here is my work summery on the Raspberry Pi.  As I start working on it and put it all together, this efforts are made to collect all the information I need, it is wise to save all my work notes.

So, first of all you should have the following items on your desk to start working on the Raspberry Pi:
I like this image from Element 14 Community.

I am done writing all the drivers and some apps that use I2C, SPI, GPIO, and other resources on the board. so, I will be updating this page soon.

Setting up the RaspberryPi:
to start here is the ID and password for the default user
ID: pi
Password: raspberry




GPIO:
There are at least two options to work with GPIOs. One is mapping a pointer to the GPIO registers and using that to manipulate IOs. Two is to use file system by opening the proper file and manipulating that.

Note:
There is a change on Raspberry pi 2 that affected the addressing of GPIO address, originally the following mapping was used on the Raspberry pi

#define BCM2708_PERI_BASE        0x20000000   

#define GPIO_BASE                (BCM2708_PERI_BASE + 0x200000)  

/* GPIO controller */

the following change will be used to map to the new Raspberry pi 2

#define BCM2708_PERI_BASE        0x3F000000  

#define GPIO_BASE                (BCM2708_PERI_BASE + 0x200000) 

/* GPIO controller */

I2C:

Will need to install:
sudo apt-get install libi2c-dev
sudo apt-get install i2c-tools

Then you will be able to run:
sudo i2cdetect -y 1
i2cget
i2cset

Now, How to read/write to I2C:




SPI:
Great news, SPI is functioning now, I am working on learning more about the process and customizing the code to work with my need as a general SPI master that can communicate with different SPI resources.


Read and Write files on micro SD Card
You can read/write files on the SD card or on a mounted USB Flash drive.
to do, you need to know first the mount point for this device.



Sound:



How to sync time with NTP server on login:
We need to edit the NTP time server list.
well, the command is

ntpdate ntp_server_address

but, I found out on the Rasspberry pi I get this message

the NTP socket is in use, exiting

So, I need to do this

sudo service ntp stop
sudo ntpdate ntp_server_address
sudo service ntp start

and now it works just fine....
You can test to see if ntpd is running,

ntpd -p

Also, need to select your proper time zone:
need to remove the timezone file first

rm localtime

now link to the correct file for your time zone

cd /etc
ln -s /usr/share/zoneinfo/US/Eastern localtime

Now when you sync it will show the correct time for your zone.


Start App automatically on boot:
to be able to run a script automatically after login, we need to edit the following file

sudo nano /etc/profile

then add the executable at the end of this file such as the commands needed to automatically execute ntp sync at login

sudo service ntp stop
sudo ntpdate ntp_server_address
sudo service ntp start

There is also cron:
cron is a software utility that is time based to run scripts in a Linux like environment.
crontab is cron table that contains all these scripts
a link is provided to read more about cron on Wikipedia web site, very good information


Bluetooth management:
Some more details to be added here once I am finished with it...



Links to resources:

http://mitchtech.net/raspberry-pi-arduino-spi/

http://www.raspberry-projects.com/pi/programming-in-c/spi/using-the-spi-interface

http://askubuntu.com/questions/244526/unable-to-synchronize-time-using-ntp

http://www.opentechguides.com/how-to/article/raspberry-pi/5/raspberry-pi-auto-start.html

http://en.wikipedia.org/wiki/Cron

How to configure your Raspberry pi WiFi and Bluetooth

Interfacing to the PandaBoard GPIO, SPI, etc...

Here is my experience/adventure with PandaBoard trying to use its SPI, GPIO interfaces.

This is a work in progress so, I am documenting as I progress.

GPIO are found @

/sys/class/gpio

and then need to export as root...

#echo "50" > export
# echo "39" > export
# echo "38" > export
# echo "37" > export
# echo "out" >  gpio51/direction
# echo "out" >  gpio50/direction
# echo "out" >  gpio39/direction
# echo "out" >  gpio38/direction
# echo "out" >  gpio37/direction

# echo "1" > gpio38/value
# echo "0" > gpio38/value
# echo "1" > gpio38/value
# echo "0" > gpio38/value
# echo "1" > gpio38/value
# echo "1" > gpio37/value
# echo "0" > gpio37/value

To read from GPIO that is set as Input:
# cat /sys/class/gpio/gpio34/value

I will need to use 

chmod 666 /sys/class/gpio/gpio38/value

OR

Change the rc.local  

Now, How do I do this from C program:

This file will show in details how to do all the above from C program.
Note: You will have to run this program using sudo ./Test_IO_1 until I find how to create the GPIO on boot and make it accessible to all users
Makefile
Test_IO_1.c

I included the Makefile so you can compile the C program.  I compiled the code natively, which is on the Pandaboard itself.

1. Make a folder, Test_IO_1
2. Copy these two files to the new folder
3. run make
4. you should have Test_IO_1.0 and Test_IO_1
5. type sudo ./Test_IO_1
6. monitor GPIO38 with a scope, multimeter or a LED

Use this image or PandaBoard datasheet to find the correct pin for GPIO38

Open a file-socket to read or write from /sys/class/gpio/gpio38/value

To Read:

rewind(fp);

fread(&read_value, sizeof(char), 1, fp);

To Write:

rewind(fp);

fwrite(&set_value, sizeof(char), 1, fp);

OK, How to modify device read/write permission on boot:
I found this tile /etc/mtab
is this the one?

Also, I found SPI stuff @

/sys/class/spi_master

There is spi1, spi2, spi3, spi4

References:

http://lxr.free-electrons.com/source/Documentation/gpio.txt

http://www.haifux.org/lectures/258/gpio_spi_i2c_userspace.pdf

https://www.kernel.org/doc/Documentation/spi/spi-summary

http://www.youtube.com/watch?v=fuEB0VCkslQ

http://comments.gmane.org/gmane.comp.embedded.pandaboard/9743

http://lxr.free-electrons.com/source/drivers/input/keyboard/gpio_keys.c

http://lxr.free-electrons.com/source/arch/arm/mach-u300/spi.c?v=2.6.34

http://elinux.org/BeagleBoard/SPI

http://www.egr.msu.edu/classes/ece480/capstone/fall12/group02/documents/Mark-Birdsall_App-Note.pdf