Category Archives: Linux

Raspberry Pi with a 3.2″ TFT with Touch control

I have spent the last few weeks working on getting a SainSmart 3.2″ TFT with touch control working with my Raspberry Pi and I have had success.

You can see an update on this project here;
http://ozzmaker.com/2013/05/27/raspberry-pi-with-a-3-2-tft-with-touch-control-part-2/

PiScreen TFT Raspberry Pi

I have currently connected it up with a breadboard, I now need to work on a more permanent solution.

Download the Kernel that contains the drivers.

Click on the images for a larger view.

Graph
Graph
Click the image below for a much larger version
Graph

My setup;
M74HC4040B1R
74HC4094N
5v to TFT
3.3v to ICs
Reset through 10k resistor
Back light connected to 3.3v

I start Xwindows with sudo FRAMEBUFFER=/dev/fb1 startx -- -dpi 60

Thanks to XaLKiDEoS , Notro, drsb and  valdodov.;
http://www.raspberrypi.org/phpBB3/viewtopic.php?f=64&t=33679
http://www.valdodov.com/

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Guide to interfacing a Gyro and Accelerometer with a Raspberry Pi

A lot of people have asked how I got the readings from the Gyro, Accelerometer, and Compass inertial measurement unit(IMU) which is used to keep PiBBOT upright.

UPDATED And updated guide has been published here, with cleaner and simpler code.
BerryIMU Raspberry Pi Gyroscope Accelerometer

In this guide I will explain how to get readings from the IMU and convert these raw readings into usable angles. I will also show how to read some of the information in the datasheets for these devices. The theory and principals below can be applied to any digital IMU, just some minor modifications need to be made. Eg register values, sensitivity level…

The code can be found here;
https://github.com/mwilliams03/Raspberry-Gyro-Acc

A note about Gyros and Accelerometers

When using the IMU to calculate angles, readings from both the gyro and accelerometer are needed, which are then combined. This is because using either on their own will result in inaccurate readings.

Here is why;
Gyros – A gyro measures the rate of rotation, which has to be tracked over time to calculate the current angle. This tracking causes the gyro to drift. However, gyros are good at measuring quick sharp movements.

Accelerometers – Accelerometers are used to sense both static (e.g. gravity) and dynamic (e.g. sudden starts/stops) acceleration. They don’t need to be tracked like a gyro and can measure the current angle at any given time. Accelerometers however are very noisy and are only useful for tracking angles over a long period of time.

Here is an excellent tutorial about accelerometers and gyros;
http://www.instructables.com/id/Accelerometer-Gyro-Tutorial/?ALLSTEPS

Setting up the IMU and I2C

The IMU I use is a MinIMU-9 v2 Gyro, Accelerometer, and Compass which uses a L3GD20 3-axis gyroscope and a LSM303DLHC 3-axis accelerometer and 3-axis magnetometer.
The datasheets are needed if you want to use these devices;
L3GD20 datasheet
LSM303DLHC datasheet

This IMU communicates via the I2C interface.

From the images below, you can see how to connect it to the Raspberry Pi. You can also see the orientation of the X, Y and Z axis.

Temp 12 hour Graph Graph

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Expand the Number of GPIO Pins on the Raspberry PI

As of revision 2 boards, there is space to add some header pins to get access to eight more GPIO pins. These are found on the Header 5. Highlighted below.

Raspberry Pi P5 header

Raspberry Pi P5 header

 

 

Here are their functions;
Raspberry Pi P5 header GPIO P5

  • P5-Pin1 – 5v0
  • P5-Pin2 – 3.3v
  • P5-Pin3 – GPIO28
  • P5-Pin4 – GPIO30
  • P5-Pin5 – GPIO29
  • P5-Pin6 – GPIO31
  • P5-Pin7 – GND
  • P5-Pin8 – GND

I needed some more pins for PiBBOT as I want to change my TFT to a character OLED which needed more pins then I had spare, so I decided to make use of these extra pins.

Here are the results, I soldered the head onto the underside of the Pi so I could plug in an IDC cable.

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Success with a Balancing Robot using a Raspberry Pi

I have had success with getting PiBBOT to balance.

 

 

 

When I saw my first two wheel balancing robot I was very fascinated.  And after receiving my Raspberry Pi, I decided to build one myself.
PiBBOT (Pi Balancing roBOT) is my first successful balancing robot. And it has room for improvement and extra functionality.

When building PiBBOT, I had a few roadblocks I needed to overcome;

  1. I originally had the Anker as the power source for both Pi and the motors, however the amperage was too low.
  2. Original H-Bridge not powerful enough for my motors
  3. Gyro calculation off by 15 degrees


The TFT displays the angles from the accelerometer, gyro, complementary filter and power to the motors.
The buttons are to turn the motors on and off and to reset the gyro.

BerryIMU Raspberry Pi Gyroscope Accelerometer

What next?

  • Incorporate the wheel encoders for better balance
  • Build a sturdier frame
  • Implement direction control
  • The able to self right itself after falling over
  • Room mapping
  • Retrieve a can of beer from the fridge
PiBBOT PiBBOT TFT Motor Controller
PiBBOT TFT PiBBOT PiBBOT TFT


PiBBOT consists of these components;
Adafruit:
TFT; 2.2″ 18-bit color TFT LCD display
RF Receiver :RF M4 Receiver – 315MHz

Pololu;
Motors;  9.7:1 Metal Gearmotor 25Dx48L mm with 48 CPR Encoder
Wheels; Pololu Wheel 90x10mm
IMU; MinIMU-9 v2 Gyro, Accelerometer, and Compass (L3GD20 and LSM303DLHC).

Anker;
Battery; Anker® Astro3 10000mAh  5V / 9V / 12V 2A Dual USB Output External Battery

Tenergy;
Battery; 7.2V Tenergy 3800mAh Flat NiMH High Power


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Raspberry Pi with a 1.8″ TFT shield

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

TFT Shield TFT 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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