Category Archives: Raspberry Pi

Linux, Raspberry Pi

Raspberry Pi with a 1.8″ TFT shield

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I'm using a shield from Texy to attach my TFT to my Pi.

TFT ShieldTFT shield

This is soooo much easier then connecting up the cables individually, which requires me to always refer to the wiring diagram... and it always takes me two or three goes to get it right.

This just requires a quick snap onto the top of the GPIO pins. It also includes wiring to use 3 buttons on the GPIO pins not being used by the TFT.

Look here to find out where you can get one;
http://www.raspberrypi.org/phpBB3/viewtopic.php?f=59&t=40674







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Linux, Raspberry Pi

Automatic login between two Raspberry Pi hosts

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If you have multiple Raspberry's or even multiple Unix hosts , you will start to get frustrated at constantly having to enter a password every time you copy files between them or access these devices from another Unix host.


There is an easy way to disable this with RSA key pairs.

  1. On each host, enter ssh-keygen
  2. Hit enter to keep the default directory.
  3. Passphrase.  Leave blank and hit enter
  4. Your keys are created under .ssh/

Now you need to copy over your key to all the other hosts with;
ssh-copy-id -i .ssh/id_rsa.pub username@serverip



Once this is done, you should now be able to copy files or access each device without having to use passwords.

You still need to enter a password when trying to connect from a host that hasn't got a key.


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Linux, Raspberry Pi

Raspberry Pi with a 2.2″ TFT

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Notro has done some great work with developing drivers for different models of TFT displays for the Pi.
He successfully created one for the Adafruit 2.2" TFT . This is a great little display and is very clear.

Notro's Wiki with instructions can be found here.

As with the 1.8" TFT from Adafruit, this device can be used to display video, images and your own data with easily using pygame.

A couple of images from my Pi running the 2.2 TFT;

photo2.2TFT

PiTFT22-1

 

 
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Balancing Robot, Linux, Raspberry Pi

PiBBot – Robotic Project – Phase 2 – Prototype

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Here is my first attempt at getting PiBBot balanced.

This is a very early prototype, confirming that all the hardware works and the I can get the time of the main loop down to 20ms, which was easy.
This prototype also helped me get my head around the code and math need to balance.

 

 

I am waiting on the delivery of some hardware to build my final and larger version.  Which will have a battery pack placed up high, this will help a lot with the balancing.

1stBalance2

 

The main components used to balance this prototype;

  • MinIMU-9 v2 Gyro, Accelerometer, and Compass (L3GD20 and LSM303DLHC Carrier)
  • Solarbotics GM6 120:1 Mini Gear Motor Offset Output
  • Dual H-Bridge Motor Driver
  • 315MHz RF M4 Receiver
  • 12v battery

The receiver allowed my to change the PID values in real time.

There is also a lot of other components on the breadboard, but they are not needed to balance. Eg TFT, 8x8Matrix, Temp monitor...



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Linux, Raspberry Pi

Setting up VNC on Raspberry Pi

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I run my Pi headless and every now and than I need to access the GUI.
Rather than connecting up a monitor, keyboard and mouse, I use TightVNC.

Below are some quick instructions on how to get this working.



- Install TightVNC

pi@raspberrypi ~ $ sudo apt-get update
pi@raspberrypi ~ $ sudo apt-get install tightvncserver


-To start VNC. When running it for the first time you will be asked for a password.

pi@raspberrypi ~ $ vncserver :1 -geometry 1200x768 -depth 24



-To connect to your Pi from another PC, use TightVNC viewer.
VNC viewer






-To stop TightVNC on your Pi.

pi@raspberrypi ~ $ vncserver -kill :1

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Balancing Robot, Linux, Raspberry Pi

PiBBot – Robotic Project – Phase 1 – Testing Components

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This is the first phase on my Balancing Robot project.
Which I think I will call PiBBot. (Pi balancing Bot)

I want to test all the components first before I put them in their final position on the frame for my balancing robot.

Components2
Components1

Hardware list;

  • Raspberry Pi rev 2
  • Two breadboards
  • 1.8" TFT, connected via SPI
  • Three 8x8 led matrix's connected via I2C
  • One MinIMU  (Accelerometer, Gyro & Compass) all connected via I2C
  • H-Bridge to control the motors
  • Temperature sensor connected via I2C
  • 315Mhz RF Receiver
  • One LED

Click the image below to see the components named on the breadboard;
Breadboard with Labels

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Linux, Raspberry Pi

Raspberry Pi and an 8×8 LED Matrix, using C.

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Below is some information on how to get an 8x8 led matrix working on your Raspberry Pi using C.
I have also included the code needed to get text scrolling.

The matrix I am using is this one from Adafruit. This matrix uses a HT16K33 controller chip and communicates with the Pi via the i2c bus.


Adafruit has very good and detailed tutorials on how to solder it up and get i2c working between your Pi and the Matrix.
http://learn.adafruit.com/adafruit-led-backpack/
http://learn.adafruit.com/matrix-7-segment-led-backpack-with-the-raspberry-pi/configuring-your-pi-for-i2c


In brief;

  1. Scan the i2c bus for your device.
  2. Download the code needed.
  3. Compile.
  4. Run.



1. Scan i2c bus

Adafruit have some great instructions in the links above on how to do this.
When using i2cdetect to scan my bus, 0x70 was returned for the address of my matrix.
I am using a Rev B board and my bus is 1. If you get nothing back, check bus 0 with i2cdetect -y 0.

pi@raspberrypi ~ $sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: 70 -- -- -- -- -- -- --
pi@raspberrypi ~ $




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Linux, Raspberry Pi

Raspberry Pi, 1.8″ TFT, RF Receiver and Temperature Sensor

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Below is some detail regarding the latest project I have been working on. Which is near completion.
I plan to wire it up permanently, place within a case and wall mount it.

 

 

Some of the images don't come up too great in the video, I have included the actual images used here;

Temp12 hour GraphGraph
TextText

I created a simple one line bash script that polls for the temperature every 5 mins.

The main python program uses pygame to write to the TFT via a framebuffer and Matplotlib is used to create the Graphs.
The display can be changed by either the button on the breadboard or via the remote FOB.

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Linux, Raspberry Pi

How to Test the SD Card Speed on Your Raspberry Pi

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Some of us will have multiple SD cards lying around. And sometimes it isn't obvious which one is the best to use.

Here is how you can check the speed of your SD cards which may help you with choosing the fastest one.

hdparm is a good tool to view disks reads, from the disk and from the buffer. We will use two options for hdparm;

  1. The speed of reading directly from the Linux buffer cache without disk access. (-t option)
  2. The speed of reading through the buffer cache to the disk without any prior caching of data. (-T option)

The first shows us an indication of the throughput of the processor, cache, and memory of the system under test. The second measures how fast the drive can sustain sequential data reads, without any filesystem overhead. It is also best to run this command multiple times to see the affect of the caching.

 

Need to install hdparm, and then run it at least twice.
From my output below, you can see that the response for the cached reads increased the second time I ran hdparm.

pi@raspberrypi ~ $ sudo apt-get install hdparm
pi@raspberrypi ~ $
pi@raspberrypi ~ $ sudo hdparm -tT /dev/mmcblk0  /dev/mmcblk0:
Timing cached reads: 104 MB in 2.01 seconds = 51.67 MB/sec
Timing buffered disk reads: 58 MB in 3.03 seconds = 19.12 MB/sec
pi@raspberrypi ~ $ sudo hdparm -tT /dev/mmcblk0  /dev/mmcblk0:
Timing cached reads: 188 MB in 2.03 seconds = 92.76 MB/sec
Timing buffered disk reads: 60 MB in 3.03 seconds = 19.83 MB/sec
pi@raspberrypi ~ $

 

 

DD can also be used to test SD card speeds.
WARNING: you must be careful using DD as incorrect options can erase your SD card.

This command will write a 200MB file called test to the SD Card;
dd if=/dev/zero of=test bs=1048576 count=200

This command will read the 200MB file created in the first command;
dd if=test of=/dev/null bs=1048576

 

pi@raspberrypi ~ $ dd if=/dev/zero of=test bs=1048576 count=200
200+0 records in
200+0 records out
209715200 bytes (210 MB) copied, 9.6409 s, 21.8 MB/s
pi@raspberrypi ~ $
pi@raspberrypi ~ $ dd if=test of=/dev/null bs=1048576
200+0 records in
200+0 records out
209715200 bytes (210 MB) copied, 10.2369 s, 20.5 MB/s
pi@raspberrypi ~ $

 


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Linux, Raspberry Pi

View images as ASCII in the terminal on a Raspberry Pi

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I run my Raspberry Pi headless and I don't like to access X windows.
Sometimes I need to look at an image, mostly PNG. I use my Pi to produce graphs and I want to see if the change took.

cacaview allows me to view the images as ASCII in the terminal. Which allows me to have a quick look at the image, and it also looks kinda cool and retro.


Cacaview Raspberry Pi



Install and using cacaview


Installing cacaview:

pi@raspberrypi ~ $sudo apt-get install caca-utils


To view an image:

pi@raspberrypi ~ $cacaview gp.png


+ Zoom in
- Zoom out
d Change differ
hjkl Move



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