Added a GPIO driver using the sysfs filesystem

CMakeLists.txt

+# Pre-requisites about cmake itself
+CMAKE_MINIMUM_REQUIRED(VERSION 2.4)
+
+if(COMMAND cmake_policy)
+  cmake_policy(SET CMP0005 NEW) 
+  cmake_policy(SET CMP0003 NEW)
+   
+endif(COMMAND cmake_policy)
+
+# The project name and the type of project
+PROJECT(bbb-gpio)
+
+SET(EXECUTABLE_OUTPUT_PATH ${CMAKE_CURRENT_SOURCE_DIR}/bin)
+SET(LIBRARY_OUTPUT_PATH ${CMAKE_CURRENT_SOURCE_DIR}/lib)
+SET(CMAKE_INSTALL_PREFIX /usr/local)
+
+IF (NOT CMAKE_BUILD_TYPE)
+ SET(CMAKE_BUILD_TYPE "DEBUG") 
+ENDIF (NOT CMAKE_BUILD_TYPE)
+
+SET(CMAKE_CXX_FLAGS_DEBUG "-g -Wall -D_REENTRANT")
+SET(CMAKE_CXX_FLAGS_RELEASE "-O3 -D_REENTRANT")
+
+ADD_SUBDIRECTORY(src)
+
+FIND_PACKAGE(Doxygen)
+
+FIND_PATH(IRI_DOC_DIR doxygen.conf ${CMAKE_SOURCE_DIR}/doc/iri_doc/)
+IF (IRI_DOC_DIR)
+  ADD_CUSTOM_TARGET (doc ${DOXYGEN_EXECUTABLE} ${CMAKE_SOURCE_DIR}/doc/iri_doc/doxygen.conf)
+ELSE (IRI_DOC_DIR)
+  ADD_CUSTOM_TARGET (doc ${DOXYGEN_EXECUTABLE} ${CMAKE_SOURCE_DIR}/doc/doxygen.conf)
+ENDIF (IRI_DOC_DIR)
+
+ADD_CUSTOM_TARGET (distclean @echo cleaning cmake files)
+
+IF (UNIX)
+  ADD_CUSTOM_COMMAND(
+    COMMENT "distribution clean"
+    COMMAND make ARGS clean
+    COMMAND rm ARGS -rf ${CMAKE_SOURCE_DIR}/build/*
+
+    TARGET  distclean
+  )
+ELSE(UNIX)
+  ADD_CUSTOM_COMMAND(
+    COMMENT "distclean only implemented in unix"
+    TARGET  distclean
+  )
+ENDIF(UNIX)
+
+ADD_CUSTOM_TARGET (uninstall @echo uninstall package)
+
+IF (UNIX)
+  ADD_CUSTOM_COMMAND(
+    COMMENT "uninstall package"
+    COMMAND xargs ARGS rm < install_manifest.txt
+
+    TARGET  uninstall
+  )
+ELSE(UNIX)
+  ADD_CUSTOM_COMMAND(
+    COMMENT "uninstall only implemented in unix"
+    TARGET  uninstall
+  )
+ENDIF(UNIX)
+
+

Findbbb_gpio.cmake

+FIND_PATH(bbb_gpio_INCLUDE_DIR bbb_gpio.h gpioexceptions.h /usr/include/iridrivers /usr/local/include/iridrivers)
+
+FIND_LIBRARY(bbb_gpio_LIBRARY
+    NAMES bbb_gpio
+    PATHS /usr/lib/iridrivers /usr/local/lib /usr/local/lib/iridrivers) 
+
+IF (bbb_gpio_INCLUDE_DIR AND bbb_gpio_LIBRARY)
+   SET(bbb_gpio_FOUND TRUE)
+ENDIF (bbb_gpio_INCLUDE_DIR AND bbb_gpio_LIBRARY)
+
+IF (bbb_gpio_FOUND)
+   IF (NOT bbb_gpio_FIND_QUIETLY)
+      MESSAGE(STATUS "Found bbb_gpio: ${bbb_gpio_LIBRARY}")
+   ENDIF (NOT bbb_gpio_FIND_QUIETLY)
+ELSE (bbb_gpio_FOUND)
+   IF (bbb_gpio_FIND_REQUIRED)
+      MESSAGE(FATAL_ERROR "Could not find bbb_gpio")
+   ENDIF (bbb_gpio_FIND_REQUIRED)
+ENDIF (bbb_gpio_FOUND)
+

ReadMe.txt

+Copyright (C) 2009-2010 Institut de Robòtica i Informàtica Industrial, CSIC-UPC.
+Author tina (tina@iri.upc.edu)
+All rights reserved.
+
+This file is part of gpio testing library
+gpio testing library is free software: you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>
+
+

doc/doxygen.conf

+# Doxyfile 1.5.5
+
+@INCLUDE_PATH = ../doc/
+@INCLUDE = doxygen_project_name.conf
+
+#---------------------------------------------------------------------------
+# Project related configuration options
+#---------------------------------------------------------------------------
+DOXYFILE_ENCODING      = UTF-8
+PROJECT_NUMBER         = 
+OUTPUT_DIRECTORY       = ../doc
+CREATE_SUBDIRS         = NO
+OUTPUT_LANGUAGE        = English
+BRIEF_MEMBER_DESC      = YES
+REPEAT_BRIEF           = NO
+ABBREVIATE_BRIEF       = 
+ALWAYS_DETAILED_SEC    = NO
+INLINE_INHERITED_MEMB  = NO
+FULL_PATH_NAMES        = YES
+STRIP_FROM_PATH        = 
+STRIP_FROM_INC_PATH    = 
+SHORT_NAMES            = NO
+JAVADOC_AUTOBRIEF      = NO
+QT_AUTOBRIEF           = NO
+MULTILINE_CPP_IS_BRIEF = NO
+DETAILS_AT_TOP         = NO
+INHERIT_DOCS           = YES
+SEPARATE_MEMBER_PAGES  = NO
+TAB_SIZE               = 8
+ALIASES                = 
+OPTIMIZE_OUTPUT_FOR_C  = YES
+OPTIMIZE_OUTPUT_JAVA   = NO
+OPTIMIZE_FOR_FORTRAN   = NO
+OPTIMIZE_OUTPUT_VHDL   = NO
+BUILTIN_STL_SUPPORT    = NO
+CPP_CLI_SUPPORT        = NO
+SIP_SUPPORT            = NO
+DISTRIBUTE_GROUP_DOC   = NO
+SUBGROUPING            = YES
+TYPEDEF_HIDES_STRUCT   = NO
+#---------------------------------------------------------------------------
+# Build related configuration options
+#---------------------------------------------------------------------------
+EXTRACT_ALL            = NO
+EXTRACT_PRIVATE        = NO
+EXTRACT_STATIC         = NO
+EXTRACT_LOCAL_CLASSES  = YES
+EXTRACT_LOCAL_METHODS  = NO
+EXTRACT_ANON_NSPACES   = NO
+HIDE_UNDOC_MEMBERS     = NO
+HIDE_UNDOC_CLASSES     = NO
+HIDE_FRIEND_COMPOUNDS  = NO
+HIDE_IN_BODY_DOCS      = NO
+INTERNAL_DOCS          = NO
+CASE_SENSE_NAMES       = YES
+HIDE_SCOPE_NAMES       = NO
+SHOW_INCLUDE_FILES     = YES
+INLINE_INFO            = YES
+SORT_MEMBER_DOCS       = NO
+SORT_BRIEF_DOCS        = NO
+SORT_GROUP_NAMES       = NO
+SORT_BY_SCOPE_NAME     = NO
+GENERATE_TODOLIST      = YES
+GENERATE_TESTLIST      = YES
+GENERATE_BUGLIST       = YES
+GENERATE_DEPRECATEDLIST= YES
+ENABLED_SECTIONS       = 
+MAX_INITIALIZER_LINES  = 30
+SHOW_USED_FILES        = YES
+SHOW_DIRECTORIES       = YES
+FILE_VERSION_FILTER    = 
+#---------------------------------------------------------------------------
+# configuration options related to warning and progress messages
+#---------------------------------------------------------------------------
+QUIET                  = YES
+WARNINGS               = YES
+WARN_IF_UNDOCUMENTED   = YES
+WARN_IF_DOC_ERROR      = YES
+WARN_NO_PARAMDOC       = NO
+WARN_FORMAT            = "$file:$line: $text"
+WARN_LOGFILE           = 
+#---------------------------------------------------------------------------
+# configuration options related to the input files
+#---------------------------------------------------------------------------
+INPUT                  = ../src \
+                         ../doc/main.dox
+INPUT_ENCODING         = UTF-8
+FILE_PATTERNS          = *.c \
+                         *.h \
+                         *.cpp
+RECURSIVE              = YES
+EXCLUDE                = 
+EXCLUDE_SYMLINKS       = NO
+EXCLUDE_PATTERNS       = *.tab.c \
+                         *.tab.h \
+                         lex* \
+                         *glr.h \
+                         *llr.h \
+                         *glr.c \
+                         *llr.c \
+                         *general.h
+EXCLUDE_SYMBOLS        = 
+EXAMPLE_PATH           = ../src/examples
+EXAMPLE_PATTERNS       = 
+EXAMPLE_RECURSIVE      = NO
+IMAGE_PATH             = ../doc/images
+INPUT_FILTER           = 
+FILTER_PATTERNS        = 
+FILTER_SOURCE_FILES    = NO
+#---------------------------------------------------------------------------
+# configuration options related to source browsing
+#---------------------------------------------------------------------------
+SOURCE_BROWSER         = YES
+INLINE_SOURCES         = NO
+STRIP_CODE_COMMENTS    = YES
+REFERENCED_BY_RELATION = YES
+REFERENCES_RELATION    = YES
+REFERENCES_LINK_SOURCE = YES
+USE_HTAGS              = NO
+VERBATIM_HEADERS       = YES
+#---------------------------------------------------------------------------
+# configuration options related to the alphabetical class index
+#---------------------------------------------------------------------------
+ALPHABETICAL_INDEX     = YES
+COLS_IN_ALPHA_INDEX    = 5
+IGNORE_PREFIX          = 
+#---------------------------------------------------------------------------
+# configuration options related to the HTML output
+#---------------------------------------------------------------------------
+GENERATE_HTML          = YES
+HTML_OUTPUT            = html
+HTML_FILE_EXTENSION    = .html
+HTML_HEADER            = 
+HTML_FOOTER            = 
+HTML_STYLESHEET        = 
+HTML_ALIGN_MEMBERS     = YES
+GENERATE_HTMLHELP      = NO
+GENERATE_DOCSET        = NO
+DOCSET_FEEDNAME        = "Doxygen generated docs"
+DOCSET_BUNDLE_ID       = org.doxygen.Project
+HTML_DYNAMIC_SECTIONS  = NO
+CHM_FILE               = 
+HHC_LOCATION           = 
+GENERATE_CHI           = NO
+BINARY_TOC             = NO
+TOC_EXPAND             = NO
+DISABLE_INDEX          = NO
+ENUM_VALUES_PER_LINE   = 4
+GENERATE_TREEVIEW      = NO
+TREEVIEW_WIDTH         = 250
+#---------------------------------------------------------------------------
+# configuration options related to the LaTeX output
+#---------------------------------------------------------------------------
+GENERATE_LATEX         = NO
+LATEX_OUTPUT           = latex
+LATEX_CMD_NAME         = latex
+MAKEINDEX_CMD_NAME     = makeindex
+COMPACT_LATEX          = NO
+PAPER_TYPE             = a4
+EXTRA_PACKAGES         = 
+LATEX_HEADER           = 
+PDF_HYPERLINKS         = YES
+USE_PDFLATEX           = NO
+LATEX_BATCHMODE        = NO
+LATEX_HIDE_INDICES     = NO
+#---------------------------------------------------------------------------
+# configuration options related to the RTF output
+#---------------------------------------------------------------------------
+GENERATE_RTF           = NO
+RTF_OUTPUT             = rtf
+COMPACT_RTF            = NO
+RTF_HYPERLINKS         = NO
+RTF_STYLESHEET_FILE    = 
+RTF_EXTENSIONS_FILE    = 
+#---------------------------------------------------------------------------
+# configuration options related to the man page output
+#---------------------------------------------------------------------------
+GENERATE_MAN           = NO
+MAN_OUTPUT             = man
+MAN_EXTENSION          = .3
+MAN_LINKS              = NO
+#---------------------------------------------------------------------------
+# configuration options related to the XML output
+#---------------------------------------------------------------------------
+GENERATE_XML           = NO
+XML_OUTPUT             = xml
+XML_SCHEMA             = 
+XML_DTD                = 
+XML_PROGRAMLISTING     = YES
+#---------------------------------------------------------------------------
+# configuration options for the AutoGen Definitions output
+#---------------------------------------------------------------------------
+GENERATE_AUTOGEN_DEF   = NO
+#---------------------------------------------------------------------------
+# configuration options related to the Perl module output
+#---------------------------------------------------------------------------
+GENERATE_PERLMOD       = NO
+PERLMOD_LATEX          = NO
+PERLMOD_PRETTY         = YES
+PERLMOD_MAKEVAR_PREFIX = 
+#---------------------------------------------------------------------------
+# Configuration options related to the preprocessor   
+#---------------------------------------------------------------------------
+ENABLE_PREPROCESSING   = YES
+MACRO_EXPANSION        = NO
+EXPAND_ONLY_PREDEF     = NO
+SEARCH_INCLUDES        = YES
+INCLUDE_PATH           = 
+INCLUDE_FILE_PATTERNS  = 
+PREDEFINED             = _USE_MPI=1
+EXPAND_AS_DEFINED      = 
+SKIP_FUNCTION_MACROS   = YES
+#---------------------------------------------------------------------------
+# Configuration::additions related to external references   
+#---------------------------------------------------------------------------
+TAGFILES               = 
+GENERATE_TAGFILE       = 
+ALLEXTERNALS           = NO
+EXTERNAL_GROUPS        = YES
+PERL_PATH              = /usr/bin/perl
+#---------------------------------------------------------------------------
+# Configuration options related to the dot tool   
+#---------------------------------------------------------------------------
+CLASS_DIAGRAMS         = YES
+MSCGEN_PATH            = 
+HIDE_UNDOC_RELATIONS   = YES
+HAVE_DOT               = YES
+CLASS_GRAPH            = YES
+COLLABORATION_GRAPH    = YES
+GROUP_GRAPHS           = YES
+UML_LOOK               = NO
+TEMPLATE_RELATIONS     = NO
+INCLUDE_GRAPH          = NO
+INCLUDED_BY_GRAPH      = NO
+CALL_GRAPH             = YES
+CALLER_GRAPH           = YES
+GRAPHICAL_HIERARCHY    = YES
+DIRECTORY_GRAPH        = NO
+DOT_IMAGE_FORMAT       = png
+DOT_PATH               = 
+DOTFILE_DIRS           = 
+DOT_GRAPH_MAX_NODES    = 50
+MAX_DOT_GRAPH_DEPTH    = 2
+DOT_TRANSPARENT        = YES
+DOT_MULTI_TARGETS      = NO
+GENERATE_LEGEND        = YES
+DOT_CLEANUP            = YES
+#---------------------------------------------------------------------------
+# Configuration::additions related to the search engine   
+#---------------------------------------------------------------------------
+SEARCHENGINE           = NO

doc/doxygen_project_name.conf

+PROJECT_NAME = "gpio testing"

doc/main.dox

+/*! \mainpage gpio testing
+
+  \section Introduction 
+
+  \subsection Pre-Requisites
+
+  This package requires of the following libraries and packages
+	 - <A href="http://www.cmake.org">cmake</A>, a cross-platform build system.
+	 - <A href="http://www.doxygen.org">doxygen</a> and 
+	   <A href="http://www.graphviz.org">graphviz</a> to generate the documentation.
+         - stdc++, 
+	 .
+  
+  Under linux all of these utilities are available in ready-to-use packages.
+
+  Under MacOS most of the packages are available via <a href="http://www.finkproject.org/">fink</a>. <br>
+
+  \subsection Compilation
+
+  Just download this package, uncompress it, and execute
+   - cd build
+   - cmake ..
+   .
+  to generate the makefile and then
+   - make
+   .
+  to obtain the shared library (in this case called <em>iriutils.so</em>) and
+  also all the example programs.
+
+  The <em>cmake</em> only need to be executed once (make will automatically call
+  <em>cmake</em> if you modify one of the <em>CMakeList.txt</em> files).
+
+  To generate this documentation type
+       - make doc
+       .
+
+  The files in the <em>build</em> directory are genetated by <em>cmake</em>
+  and <em>make</em> and can be safely removed.
+  After doing so you will need to call cmake manually again.
+
+  \subsection Configuration
+
+  The default build mode is DEBUG. That is, objects and executables 
+  include debug information.
+
+  The RELEASE build mode optimizes for speed. To build in this mode
+  execute
+      - cmake .. -DCMAKE_BUILD_TYPE=RELEASE
+      .
+  The release mode will be kept until next time cmake is executed.
+
+  \subsection Installation
+
+  In order to be able to use the library, it it necessary to copy it into the system.
+  To do that, execute
+
+      - make install
+      .
+
+  as root and the shared libraries will be copied to <em>/usr/local/lib/iriutils</em> directory
+  and the header files will be copied to <em>/usr/local/include/iriutils</em> dierctory. At 
+  this point, the library may be used by any user.
+
+  To remove the library from the system, exceute
+      - make uninstall
+      .
+  as root, and all the associated files will be removed from the system.
+
+  \section Customization
+
+  To build a new application using these library, first it is necessary to locate if the library
+  has been installed or not using the following command
+
+      - FIND_PACKAGE(bbb_gpio REQUIRED)
+
+  In the case that the package is present, it is necessary to add the header files directory to
+  the include directory path by using
+
+      - INCLUDE_DIRECTORIES(${bbb_gpio_INCLUDE_DIR})
+
+  Finally, it is also nevessary to link with the desired libraries by using the following command
+
+      - TARGET_LINK_LIBRARIES(<executable name> ${bbb_gpio_LIBRARY})
+      .
+
+  \section License
+
+  This package is licensed under a  
+  <a href="http://www.gnu.org/licenses/lgpl.html">
+    LGPL 3.0 License</a>.
+
+  \section Disclaimer
+
+   This is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>. 
+
+ */

src/CMakeLists.txt

+# edit the following line to add all the source code files of the library
+SET(sources bbb_gpio.cpp gpioexceptions.cpp)
+# edit the following line to add all the header files of the library
+SET(headers bbb_gpio.h gpioexceptions.h)
+
+# edit the following line to find the necessary packages
+FIND_PACKAGE(iriutils REQUIRED)
+
+INCLUDE_DIRECTORIES(${iriutils_INCLUDE_DIR} ./)
+
+ADD_LIBRARY(bbb_gpio SHARED ${sources})
+
+#edit the following line to add the necessary system libraries (if any)
+TARGET_LINK_LIBRARIES(bbb_gpio pthread rt)
+TARGET_LINK_LIBRARIES(bbb_gpio ${iriutils_LIBRARY})
+
+INSTALL(TARGETS bbb_gpio
+  RUNTIME DESTINATION bin
+  LIBRARY DESTINATION lib/iridrivers
+  ARCHIVE DESTINATION lib/iridrivers
+)
+
+INSTALL(FILES ${headers} DESTINATION include/iridrivers)
+
+INSTALL(FILES ../Findbbb_gpio.cmake DESTINATION ${CMAKE_ROOT}/Modules/)
+
+ADD_SUBDIRECTORY(examples)

src/bbb_gpio.cpp

+#include "gpioexceptions.h"
+#include "bbb_gpio.h"
+#include <iostream>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+
+CGPIO::CGPIO(gpio_ports port,int pin)
+{
+  int fp; 
+  std::stringstream text;
+
+  /* try to export the desired pin */
+  if((fp=open("/sys/class/gpio/export",O_WRONLY))==-1)
+  {  
+    /* handle exceptions */
+    throw CGPIOException(_HERE_,"Impossible to export the desired port pin");
+  }
+  // set the file pointer to the beginning
+  lseek(fp,0,SEEK_SET);
+  // select the desired GPIO index
+  if(pin < 0 || pin > 31)
+  {
+    /* handle exceptions */
+    close(fp);
+    throw CGPIOException(_HERE_,"Invalid pin identifier");
+  }
+  this->gpio_id=(int)port+pin;
+  text << this->gpio_id;
+  if(write(fp,text.str().c_str(),text.str().size())!=(int)text.str().size())
+  {
+    /* handle exceptions */
+    close(fp);
+    throw CGPIOException(_HERE_,"Error while writing to the export file");
+  }
+  // close the export file
+  close(fp);
+  // initialize internal parameters
+  this->direction=input;
+  this->edge=edge_none;
+  this->event_server=CEventServer::instance();
+  text.str(std::string(""));
+  text << "pin_" << this->gpio_id << "_finish_thread_event";
+  this->finish_thread_event_id=text.str();
+  this->event_server->create_event(this->finish_thread_event_id);
+  this->thread_server=CThreadServer::instance();
+  text.str(std::string(""));
+  text << "pin_" << this->gpio_id << "_thread";
+  this->edge_thread_id=text.str();
+  this->thread_server->create_thread(this->edge_thread_id);
+  this->thread_server->attach_thread(this->edge_thread_id,this->edge_thread,this);
+  this->input_fd=-1;
+
+  // wait for the pin to be available
+  sleep(1);
+}
+
+void *CGPIO::edge_thread(void *param)
+{
+  CGPIO *gpio=(CGPIO *)param;
+  unsigned char buffer[1024];
+  int error,max_fd=0;
+  fd_set wait_set;
+  bool end=false;
+  timeval time;
+
+  while(!end)
+  {
+    if(gpio->event_server->event_is_set(gpio->finish_thread_event_id))
+      end=true;
+    else
+    {
+      time.tv_sec=1;
+      time.tv_usec=0;
+      FD_ZERO(&wait_set);
+      FD_SET(gpio->input_fd,&wait_set);
+      max_fd=gpio->input_fd;
+      error=select(max_fd+1,NULL,NULL,&wait_set,&time);
+      if(error==-1)
+      {
+        if(errno!=EINTR)
+        {
+          /* handle exceptions */
+          throw CGPIOException(_HERE_,"Unexpected error while waiting the activation of one the events");
+        }
+      }
+      else if(error==0)
+      {
+        /* timeout, do nothing */
+      }
+      else
+      {
+        lseek(gpio->input_fd,0,SEEK_SET);
+        read(gpio->input_fd,buffer,1024);
+        if(FD_ISSET(gpio->input_fd,&wait_set))
+          if(!gpio->event_server->event_is_set(gpio->edge_event_id))
+            gpio->event_server->set_event(gpio->edge_event_id);
+      }
+    }
+  }
+
+  pthread_exit(NULL);
+}
+
+void CGPIO::set_direction(dir_t direction)
+{
+  int fp;
+  std::stringstream text;
+
+  //Open the GPIO's sysfs file for writing
+  text << "/sys/devices/virtual/gpio/gpio" << this->gpio_id << "/direction";
+  if((fp=open(text.str().c_str(), O_WRONLY)) == -1)
+  {
+    /* handle exceptions */
+    throw CGPIOException(_HERE_,"Impossible to open the direction file");
+  }
+  //Set pointer to begining of the file
+  lseek(fp,0,SEEK_SET);
+  //Write our value of "out" to the file
+  text.str(std::string());
+  if(direction==input)
+    text << "in";
+  else
+  {
+    text << "out";
+    // finish the thread if it is active
+    if(this->thread_server->get_thread_state(this->edge_thread_id)==starting || 
+       this->thread_server->get_thread_state(this->edge_thread_id)==active)
+    {
+      this->event_server->set_event(this->finish_thread_event_id);
+      this->thread_server->end_thread(this->edge_thread_id);
+      this->event_server->reset_event(this->finish_thread_event_id);
+    }
+    // close the input file
+    close(this->input_fd);
+    this->input_fd=-1;
+  }
+  if(write(fp,text.str().c_str(),text.str().size())!=(int)text.str().size())
+  {
+    close(fp);
+    throw CGPIOException(_HERE_,"Error while writing to the direction file");
+  }
+  close(fp);
+
+  this->direction=direction;
+}
+
+void CGPIO::set_value(bool value)
+{
+  int fp;
+  std::stringstream text;
+
+  if(this->direction==output)
+  {
+    //Open the GPIO's sysfs file for reading and writing
+    text << "/sys/devices/virtual/gpio/gpio" << this->gpio_id << "/value";
+    if((fp=open(text.str().c_str(),O_RDWR)) == -1)
+    {
+      /* handle exceptions */
+      throw CGPIOException(_HERE_,"Impossible to open the value file");
+    }
+    //Set pointer to begining of the file
+    lseek(fp,0,SEEK_SET);
+    //Write our value of "1" to the file 
+    text.str(std::string());
+    if(value)
+      text << 1;
+    else
+      text << 0;
+    if(write(fp,text.str().c_str(),text.str().size())!=(int)text.str().size())
+    {
+      close(fp);
+      throw CGPIOException(_HERE_,"Error while writing to the value file");
+    }
+    close(fp);
+  }
+}
+
+bool CGPIO::get_value(void)
+{
+  return false;
+}
+
+std::string CGPIO::set_active_edge(edge_t edge)
+{
+  int fp; 
+  std::stringstream text;
+  unsigned char buffer[1024];
+
+  //Open the GPIO's sysfs file for reading and writing
+  text << "/sys/devices/virtual/gpio/gpio" << this->gpio_id << "/edge";
+  if((fp=open(text.str().c_str(),O_WRONLY)) == -1)
+  {
+    /* handle exceptions */
+    throw CGPIOException(_HERE_,"Impossible to open the edge file");
+  }
+  //Set pointer to begining of the file
+  lseek(fp,0,SEEK_SET);
+  //Write our value of "1" to the file 
+  text.str(std::string());
+  switch(edge)
+  {
+    case edge_none: text << "none";
+                    break;
+    case edge_rising: text << "rising";
+                      break;
+    case edge_falling: text << "falling";
+                       break;
+    case edge_both: text << "both";
+                     break;
+  }
+  if(write(fp,text.str().c_str(),text.str().size())!=(int)text.str().size())
+  {
+    close(fp);
+    throw CGPIOException(_HERE_,"Error while writing to the edge file");
+  }
+
+  close(fp);
+
+  this->edge=edge;
+
+  // open the input file
+  text.str(std::string(""));
+  text << "/sys/devices/virtual/gpio/gpio" << this->gpio_id << "/value";
+  if((this->input_fd=open(text.str().c_str(),O_RDONLY|O_NONBLOCK)) == -1)
+  {
+    /* handle exceptions */
+    throw CGPIOException(_HERE_,"Impossible to open the value file");
+  }
+  //Set pointer to begining of the file
+  lseek(this->input_fd,0,SEEK_SET);
+  read(this->input_fd,buffer,1024);
+  if(this->edge!=edge_none)
+  {
+    if(this->thread_server->get_thread_state(this->edge_thread_id)==attached)
+    {
+      // start the waiting thread
+      this->thread_server->start_thread(this->edge_thread_id);
+      // create the edge event
+      text.str(std::string(""));
+      text << "pin_" << this->gpio_id << "_event";
+      this->edge_event_id=text.str();
+      this->event_server->create_event(this->edge_event_id);
+    }
+  }
+  else
+  {
+    if(this->edge_event_id!="")
+      this->event_server->delete_event(this->edge_event_id);
+    this->edge_event_id="";
+  }
+
+  return this->edge_event_id;
+}
+
+CGPIO::~CGPIO()
+{
+  int fp; 
+  std::stringstream text;
+
+  // finish the thread if necessary
+  if(this->thread_server->get_thread_state(this->edge_thread_id)==starting || 
+     this->thread_server->get_thread_state(this->edge_thread_id)==active)
+  {
+    this->event_server->set_event(this->finish_thread_event_id);
+    this->thread_server->end_thread(this->edge_thread_id);
+    this->event_server->delete_event(this->edge_event_id);
+    this->edge_event_id="";
+  }
+  this->event_server->delete_event(this->finish_thread_event_id);
+  this->finish_thread_event_id="";
+  this->thread_server->detach_thread(this->edge_thread_id);
+  this->thread_server->delete_thread(this->edge_thread_id);
+  this->edge_thread_id="";
+  
+  // cloe the input file descriptor if necessary
+  if(this->input_fd!=-1)
+  {
+    close(this->input_fd);
+    this->input_fd=-1;
+  }
+
+  /* try to unexport the desired pin */
+  if((fp=open("/sys/class/gpio/unexport",O_WRONLY))==-1)
+  {  
+    /* handle exceptions */
+    throw CGPIOException(_HERE_,"Impossible to unexport the desired port pin");
+  }
+  // set the file pointer to the beginning
+  lseek(fp,0,SEEK_SET);
+  text << this->gpio_id;
+  if(write(fp,text.str().c_str(),text.str().size())!=(int)text.str().size())
+  {
+    /* handle exceptions */
+    close(fp);
+    throw CGPIOException(_HERE_,"Error while writing to the unexport file");
+  }
+  // close the export file
+  close(fp);
+}

src/bbb_gpio.h

+#ifndef BBB_GPIO_H
+#define BBB_GPIO_H
+
+#include "eventserver.h"
+#include "threadserver.h"
+
+typedef enum {output=0,input=1} dir_t;
+
+typedef enum {edge_none=0,edge_rising,edge_falling,edge_both} edge_t;
+
+typedef enum {GPIO0=0,GPIO1=32,GPIO2=64,GPIO3=96} gpio_ports;
+
+class CGPIO
+{
+  private:
+    int input_fd;
+    int gpio_id;
+    dir_t direction;
+    edge_t edge;
+    /* events */
+    std::string edge_event_id;
+    std::string finish_thread_event_id;
+    CEventServer *event_server;
+    /* threads */
+    std::string edge_thread_id;
+    CThreadServer *thread_server;
+  protected:
+    static void *edge_thread(void *param);
+  public:
+    CGPIO(gpio_ports port, int pin);
+    void set_direction(dir_t direction);
+    void set_value(bool value);
+    bool get_value(void);
+    std::string set_active_edge(edge_t edge);
+    ~CGPIO();
+};
+
+#endif

src/examples/CMakeLists.txt

+# edit the following line to add the source code for the example and the name of the executable
+ADD_EXECUTABLE(test_gpio test_gpio.cpp)
+
+# edit the following line to add the necessary libraries
+TARGET_LINK_LIBRARIES(test_gpio bbb_gpio pthread)
+
+# edit the following line to add the source code for the example and the name of the executable
+ADD_EXECUTABLE(test_input_event test_input_event.cpp)
+
+# edit the following line to add the necessary libraries
+TARGET_LINK_LIBRARIES(test_input_event bbb_gpio pthread)

src/examples/test_gpio.cpp

+#include "bbb_gpio.h"
+#include "gpioexceptions.h"
+#include <iostream>
+
+int main(int argc,char *argv[])
+{
+  int i=0;
+
+  try{ 
+    CGPIO gpio(GPIO0,31);
+    gpio.set_direction(output);
+//    for(i=0;i<2;i++)
+    while(1)
+    {
+      gpio.set_value(false);
+//      sleep(1);
+      gpio.set_value(true);
+//      sleep(1);
+    }
+  }catch(CGPIOException &e){
+    std::cout << e.what() << std::endl;
+  }
+
+  return 0;
+}

src/examples/test_input_event.cpp

+#include "bbb_gpio.h"
+#include "gpioexceptions.h"
+#include "eventserver.h"
+#include <iostream>
+
+int main(int argc,char *argv[])
+{
+  CEventServer *event_server=CEventServer::instance();
+  std::list<std::string> events;
+  int i=0;
+
+  try{ 
+    CGPIO gpio(GPIO0,30);
+    gpio.set_direction(input);
+    events.push_back(gpio.set_active_edge(edge_falling));
+
+    for(i=0;i<5;i++)
+    {
+      event_server->wait_all(events);
+      std::cout << "Push button pressed" << std::endl;
+    } 
+  }catch(CGPIOException &e){
+    std::cout << e.what() << std::endl;
+  }
+   
+  return 0;
+}

src/gpioexceptions.cpp

+#include "gpioexceptions.h"
+#include <string.h>
+#include <stdio.h>
+
+const std::string comm_exception_msg="[GPIO class] - ";
+
+CGPIOException::CGPIOException(const std::string& where,const std::string& error_msg):CException(where,comm_exception_msg)
+{
+  this->error_msg+=error_msg;
+}

src/gpioexceptions.h

+#ifndef GPIO_EXCEPTIONS
+#define GPIO_EXCEPTIONS
+
+#include "exceptions.h"
+
+/**
+ * \brief 
+ *
+ */
+class CGPIOException : public CException
+{
+  public:
+    /**
+     * \brief Constructor
+     *
+     */
+    CGPIOException(const std::string& where, const std::string& error_msg);
+};
+
+#endif