LVP Software Overview

Platform

• The stable configuration runs on a Raspberry Pi 3
• The operating system is Raspbian Jessie

Additional Libraries Required

• OpenCV 3.2.0 : [https://github.com/opencv/opencv/releases]
• RaspPiCam 0.1.5 : [https://www.uco.es/investiga/grupos/ava/node/40]

For ease of build and development, the gcc toolsuite is required. The easiest way to make sure everything needed to compile and build the C++ is to follow the installation tutorial : [http://docs.opencv.org/trunk/d7/d9f/tutorial_linux_install.html]

This includes the following essential packages:

• GCC 4.4.x or later
• CMake 2.8.7 or higher
• Git
• GTK+2.x or higher, including headers (libgtk2.0-dev)
• pkg-config
• ffmpeg or libav development packages: libavcodec-dev, libavformat-dev, libswscale-dev
• libtbb2 libtbb-dev
• libdc1394 2.x
• libjpeg-dev, libpng-dev, libtiff-dev, libjasper-dev, libdc1394-22-dev

GPIO

• All three GPIO pins are initialized as inputs, with the internal pullup enabled. Thus, the pushbutton should be connected between the indicated GPIO and ground.
• GPIO 3 (pin xx) is ZOOM IN
• GPIO 21 (pin xx) is ZOOM OUT
• GPIO 22 (pin xx) is TOGGLE INVERT
• Raspian Jessie allows non sudo access to the GPIO pins by use of the system filesystem (sysfs). The pins can be set for input or ouptut, and read and written to, using file IO. However, the pullups cannot be set this way. Therefore, a helper script is used to setup the GPIO and launch the lvp-app application.

Location of Source

• The source for the lvp-app applications (including the test apps) are in /home/pi/lvp

Building the Application

• cd /home/pi/lvp/build
• cmake ..
• make

Start On Boot

In order to start the application on boot, the following modification is made to the autoboot script.

cd ~/.config/lxsession/LXDE-pi
sudo nano autostart

Add @/home/pi/lvp/start-lvp.sh on a new line.

Stop Blanking of Screen

Without keyboard or mouse activity, the screen will blank after 5 minutes. The following modifications need to be made.

• sudo nano /etc/kbd/config

Change these two lines.

# screen blanking timeout. monitor remains on, but the screen is cleared to
# range: 0-60 min (0==never) kernels I've looked at default to 10 minutes.
# (see linux/drivers/char/console.c)
BLANK_TIME=0 

# Powerdown time. The console will go to DPMS Off mode POWERDOWN_TIME
# minutes _after_ blanking. (POWERDOWN_TIME + BLANK_TIME after the last input)
POWERDOWN_TIME=0 

• sudo nano /etc/lightdm/lightdm.conf

In that file, look for: [SeatDefault]

and insert this line: xserver-command=X -s 0 dpms

Overview of Application

Here is an outline of the application

start-lvp.sh

This script sets up the GPIO and then starts the application.

app.cpp

This contains the main source. It does the following:

• Initializes the camera
• Debounces GPIO
• Applies zoom and invert events to the frames
• Displays the frames

benchmark-frame-analysis.cpp

This file contains code to benchmark various operations, and was used during development. It may be useful in the future.