SetDigitalOutput.cpp

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

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

using namespace HuboLib;

/*
Compile and link: 
    g++ SetDigitalOutput.cpp -L../ -lhubo -lpthread -lrt -o SetDigitalOutput
Run:
    sudo ./SetDigitalOutput
Purpose:
    Turns on/off a single output as specified in the command line. 
*/

void BoostThreadPriority();

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

    if (argc != 3)
    {
        printf ("Usage: \n  SetDigitalOutput <digital output to activate>\n  example: SetDigitalOutput 7 0  // this will set channel 7 to 0\n");
        return 0;
    }

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

    int outValue = 0;
    if (sscanf (argv[2], "%d", &outValue) != 1)
    {
        printf ("Value for digital output could not be determined!\n");
        return 0;
    }

    if (outValue<0 || outValue>1)
    {
        printf ("Value for digital output must be 0 or 1!\n");
        return 0;
    }

    printf ("Setting digital output %d to %d.\n", channel, outValue);
    
    // 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 until the output latch buffer is filled.
    Wait_For_MCP23017_Buffered_Values();

    unsigned char read_out_value, channel_values;
    Readback_DO_Channels (channel_values);

    printf ("Old channel values x%02X\n", channel_values);

    if (outValue)
        channel_values |=  (1 << channel);
    else
        channel_values &= ~(1 << channel);

    printf ("New channel values x%02X\n", channel_values);
    
    // Set the outputs.
    Set_DO_Channels (channel_values);

    // For the given cycle time 20ms wait should be sufficient!
    bool bResult = false;
    for (int retry=0; retry<10; retry++)
    {
        usleep(2L*1000L);
        Readback_DO_Channels (read_out_value);
        if (read_out_value == channel_values)
        {
            bResult = true;
            break;
        }
    }

    // Free library resources.
    Uninitialize();
    
    return bResult ? 1 : 0;
}

#include <pthread.h>    
#include <assert.h>    
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);
}