AnalogInput3.cpp

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

#include "../hubolib.h"

using namespace HuboLib;

/*
Compile and link: 
    g++ AnalogInput3.cpp -L../ -lhubo -lpthread -lrt -o AnalogInput3.out
Run:
    sudo ./AnalogInput3.out
Purpose:
    Lets see how much we can use oversampling in order to increase the resolution of our ADC sample value.
*/

int main(void)
{
    // Initialize the library once in your program.
    if (!Initialize())
    {
        printf ("Error: Initialize\n");
        return 1;
    }
    
    // Define channel 0 to be oversampled 40 times (set to 40) all other channels (set to 0) are not read from the ADC.
    unsigned short overSampling[MAX_MCP3x08_CHANNELS] = { 40, 0, 0, 0, 0, 0, 0, 0 };
    Set_MCP3x08_Oversampling (overSampling);
    
    int             channel = 0;
    unsigned long   adcCount; 
    double          volt;
    for (int i=0; i<20; i++)
    {
        // Read channel 0 and output its value.
        if (Get_AI_Channel (channel, adcCount, volt))
        {
            printf ("Channel=%d   ADC count=0x%02lX   Volts=%lf\n", channel, adcCount, volt);
        }
        else 
        {
            printf ("Error: Get_AI_Channel\n");
        }

        usleep(1000);
    }

    // Let's try 41 oversamples for channel 0.
    unsigned short overSampling2[MAX_MCP3x08_CHANNELS] = { 41, 0, 0, 0, 0, 0, 0, 0 };
    if (!Set_MCP3x08_Oversampling (overSampling2))
        printf ("41 oversamples for channel 0 failed.\n");

    // Ok, let's then try to oversample channel 0 and channel 1 for 40 times.
    unsigned short overSampling3[MAX_MCP3x08_CHANNELS] = { 40, 40, 0, 0, 0, 0, 0, 0 };
    if (!Set_MCP3x08_Oversampling (overSampling3))
        printf ("40 oversamples for channel 0 and 40 oversamples for channel 1 failed.\n");
    
    // Well, how many times can I the oversample a channel?
    // This depends on the following things:
    // - the number of channels to be oversampled,
    // - the number of oversamples for each channel and
    // - the cycle time which should be kept.
    // Of cause it also depends on the CPU load of the Raspi...
    
    // Test 30 oversamples for channel 0 and 10 for channel 1.
    unsigned short overSampling4[MAX_MCP3x08_CHANNELS] = { 30, 10, 0, 0, 0, 0, 0, 0 };
    if (Set_MCP3x08_Oversampling (overSampling4))
        printf ("30 oversamples for channel 0 and 10 oversamples for channel 1 worked.\n");

    // Test 8 oversamples for channel 0, 12 for channel 1, 10 for channel 5 and 10 for channel 7.
    unsigned short overSampling5[MAX_MCP3x08_CHANNELS] = { 8, 12, 0, 0, 0, 10, 0, 10 };
    if (Set_MCP3x08_Oversampling (overSampling5))
        printf ("Oversampling 8/12/10/10 for several channels worked.\n");
        
    // Conclusion: For the given cycle time we can have a total of 40 oversamples shared amongst 
    // all of our 8 analog input channels.
    
    // Free library resources.
    Uninitialize();
    
    return 0;
}