GetDigitalInput.cpp

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#include <stdio.h>
#include <unistd.h>
#include <pthread.h>    
#include <assert.h>    

#include "../hubolib.h"
#include "../hubocfg.h" // Required for changing default I2C device.

using namespace HuboLib;

/*
Compile and link: 
    g++ GetDigitalInput.cpp -L../ -lhubo -lpthread -lrt -o GetDigitalInput
Run:
    sudo ./GetDigitalInput
Purpose:
    Reads the digital input as specified in the command line and returns the result.
*/

void BoostThreadPriority();

int main(int argc, char* argv[])
{
    // Lets have this program finish as soon as possible.
    BoostThreadPriority();

    if (argc != 2)
    {
        printf ("Usage: \n  GetDigitalInput <digital input to read>\n  example: GetDigitalInput 7  // this will read digital input 7 and return the result\n");
        return 0;
    }

    int channel = 0;
    if (sscanf (argv[1], "%d", &channel) != 1)
    {
        printf ("Digital input could not be determined!\n");
        return 0;
    }

    // If required - set the I2C device to work with. The Raspberry Pi uses "/dev/i2c-1" which is default, the Banana Pi uses "/dev/i2c-0"
    #ifdef BPI
        g_I2CConfig.m_sI2CDevice = "/dev/i2c-0";
    #endif

    // Initialize the library once in your program.
    if (!Initialize())
    {
        printf ("Error: Initialize\n");
        return 0;
    }
    
    // Set the cycle time to 2ms (50Hz).
    Set_Cycle_Time(20);
    
    // Wait for input buffers to be filled.
    Wait_For_MCP23017_Buffered_Values();

    // Finally get the output.
    bool bOutValue = false;
    bool bResult = Get_DI_Channel (channel, bOutValue);

    // Free library resources.
    Uninitialize();
    
    printf ("%s\n", bOutValue ? "1" : "0");

    return bResult;
}

void BoostThreadPriority()
{
    // Scheduling params.
    sched_param param;
    int         policy;
    int         ret;
    pthread_t   threadHandle = pthread_self();

    // Get current scheduling parameters of thread.
    ret             = pthread_getschedparam (threadHandle, &policy, &param);
    assert (ret == 0);

    // Set scheduling parameters of thread to real time values (FIFO scheduling type and max prio).
    policy               = SCHED_FIFO; // SCHED_RR;
    param.sched_priority = sched_get_priority_max(policy); // New max priority for new scheduling concept.
    ret                  = pthread_setschedparam(threadHandle, policy, &param);
    assert (ret == 0);
}