使用 OpenCV 和 BCM2835 在 Raspberry Pi 上工作

Question

I am currently working on Raspberry Pi and using the Raspberry Pi camera module. I plan to use OpenCV for image processing on the RPi and currently it seems not much of a problem. However, I am trying to use the BCM2835 library along with OpenCV and not able to integrate it. I tried to make changes in the Makefile and adding the bcm library and also adding path of the BCM library but nothing seems to work. Please help me to integrate both the libraries as I wish to drive the GPIOs after doing some image processing on the input video.

Thank you.

Answer 1

I finally found the answer to my own question. The bcm library which can be downloaded here: http://www.airspayce.com/mikem/bcm2835/

are unziped and the following files are pasted in the current folder where we are working which contains the cpp files. bcm2835.h bcm2835.o bcm2835.c

I added the bcm2835.c in the add_executable of CMakeLists.txt as follows: add_executable(camcv_vid2 bcm2835.c RaspiCamControl.c RaspiCLI.c RaspiPreview.c camcv_vid2.cpp)

Add the bcm2835.h in the program: extern "C" { ..

include "bcm2835.h"

.. }

Initialize the GPIO using bcm2835_init() in the main function and you are good to go. Use the GPIOs to your benefit. Overall, it is a combination of combining C and C++ files along with modifications in the CMakeLists.txt

Enjoy!

Answer 2

Although the topic is over 5 years old, I still find the need to add an answer, since I have been working on this now as well and found an alternative method. This method does not require to add the bcm2835.c file to add_executable but uses the pre-compiled library and links it

I am running Ubuntu 20.04.1 LTS on a Raspberry Pi 3 B

Setting up the library

1. Download bcm2835 library using: wget http://www.airspayce.com/mikem/bcm2835/bcm2835-1.xx.tar.gz;
2. Install libary using instructions on the website :
   1. # download the latest version of the library, say bcm2835-1.xx.tar.gz, then:
   2. tar zxvf bcm2835-1.xx.tar.gz
   3. cd bcm2835-1.xx
   4. ./configure
   5. make
   6. sudo make check
   7. sudo make install
3. In the CMakeLists.txt file add find_library(BCM2835_LIB bcm2835)
4. Make sure the library is linked to the target using target_link_libraries(<target name> ${BCM2835_LIB})
5. Adding the extern "C" part is not necessary (anymore), since this is taken care of in the header file of the library.
6. Initialize the GPIO's bcm2835_init() in the script file

For building I did the following:

1. Create a build folder using mkdir build and go to the folder cd build
2. Run cmake .. which sets up the compiling settings and environment
3. Run make <target name> to create the target executable or run make all to create all targets executables

Created a cpp-file called main.cpp based off blink.c ( source ) that worked:

#include "bcm2835.h"
using namespace std;
#define PIN RPI_BPLUS_GPIO_J8_07 // pin 4

int main(int argc, char **argv)
{
    if (!bcm2835_init())
        return 1;

    // Set the pin to be an output
    bcm2835_gpio_fsel(PIN, BCM2835_GPIO_FSEL_OUTP);

    // Blink
    while (1)
    {
        // Turn it on
        bcm2835_gpio_write(PIN, HIGH);

        // wait a bit
        delay(500);
        // turn it off
        bcm2835_gpio_write(PIN, LOW);
        // wait a bit
        delay(500);
    }

    return 0;

}

CMakeLists.txt file

#Declare the version of the CMake API for forward-compatibility
cmake_minimum_required(VERSION 2.8)

#Declare the name of the CMake Project
project(main)

find_library(BCM2835_LIB bcm2835)
if(NOT BCM2835_LIB)
  message(FATAL_ERROR "bcm2835_lib library not found")
else()
  message(STATUS "bcm2835_lib library found")
endif()

# Add the directory to search for header files
include_directories(include)

# Define an executable target 
add_executable(main main.cpp)
target_link_libraries(main ${BCM2835_LIB})