In this post, I show a simple application of the analog to digital converter (ADC) C++ class implementation shown previously in this post. Remembering that the BeagleBone has 7 analog inputs and ADC of 12 bits that let to de user to represent an analog signal within a range of 4096 values. It is important to remember that the reference for analog voltage is 1.8V. If the user provides a greater voltage, the BeagleBone could be damaged.

Circuit and components

The circuit can be seen in Figure 1. It consists of a Potentiometer with a power supplied using the analog ground pin 0V located at the pin P9_34 and to analog VDD pin at 1.8V located at the pin P9_32. Finally, its output is connected to the P9_39 pin.

The components are:

• 1 Potentiometer of 200KΩ
• Jumpers male-male to make the connections

Coding

First an ADC class object is declared, for example:

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ADC adcPin(P9_39);

An integer variable is declared and initialized to store the digital converted values.

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int adcValue = 0;

The digital values can be obtained through the next class method:

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adcValue = adcPin.ReadADC();

Now, this method can be inside of a for loop to take 100 readings for example every 100 milliseconds:

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for (int i = 0; i < 100; i++)
  {
    adcValue = adcPin.ReadADC();
    cout << "Reading " << i+1 << " of " << " 100: ";
    cout << adcValue << endl;
    adcPin.Delayms(100);
  }

The complete code for this application is shown in the next listing together with its corresponding execution video.

Listing_5.1

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#include <iostream>
#include "../../Sources/ADC.h"

using namespace std;

int main()
{
  string message = "Main program starting here...";
  cout << RainbowText(message,"Blue", "White", "Bold") << endl;
  
  message = "Setting  ADC mode on a pin";
  cout << RainbowText(message, "Blue") << endl;
  ADC adcPin(P9_39);

  message = "Read an analog value and wait 100 milliseconds between each read";
  cout << RainbowText(message, "Blue") << endl;

  int adcValue = 0;
  for (int i = 0; i < 100; i++)
  {
    adcValue = adcPin.ReadADC();
    cout << "Reading " << i+1 << " of " << " 100: ";
    cout << adcValue << endl;
    adcPin.Delayms(100);
  }

  message = "Main program finishes here...";
  cout << RainbowText(message,"Blue", "White","Bold") << endl;

  return 0;
}

Execution of the program:

Se you in the next post.