TVZ Mechatronics Team


Zagreb University of Applied Sciences, Professional Study in Mechatronics

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Analog inputs and outputs

Table of Contents

  1. Exercise 1: Using potenciometers as analog inputs
  2. Exercise 2: Generating waveforms using analog output
  3. Exercise 3: Analog communication between two mbeds

All exercises in this topic will be carried out using an mbed application board. The board has 3 inputs prepared for use with an AnalogIn class. Two potenciometers (Pot1 and Pot2) are connected to pins p19 and p20, respectively, and 3.5 mm audio jack is connected to pin p17.

Since mbed NXP LPC1768 has only one analog output on pin p18 for use with an AnalogOut class, mbed application board uses that output via another 3.5 mm audio jack.

You will examine the use of potenciometers as analog inputs in Exercise 1, analog outputs in Exercise 2 and analog communication between two mbeds in Exercise 3.

Exercise 1: Using potenciometers as analog inputs

Write a program that will read the inputs of potentiometers Pot1 and Pot2, calculate the average reading of two potentiometers, and based on the average reading value, turn on or off the four onboard mbed LEDs. Use the following table as rules for LEDs control:

Average reading xLED1LED2LED3LED4
x <= 0.20000
0.2 < x <= 0.41000
0.4 < x <= 0.61100
0.6 < x <= 0.81110
0.8 < x <= 11111

Write your own solution of the program, test it and then compare to the solution given below.

Import programMAB_Potenciometers

Using potenciometers as analog inputs.

Last commit 17 Dec 2014 by TVZ Mechatronics Team

Exercise 2: Generating waveforms using analog output

Write a program that generates a simple sawtooth waveform.

One possible solution is given in the program below.

Import programMAB_Waveforms_A

A simple sawtooth waveform generator using analog output.

Last commit 18 Dec 2014 by TVZ Mechatronics Team

The oscillogram is shown in the following figure:

Modify the above program to generate smoother sawtooth waveform, with the period kept the same (10 ms). Let the smoothness of the waveform be defined by the potentiometer Pot1, with a value of 0 meaning the above case (not smoothed), and a value of 1 meaning nice smooth waveform.

The solution is given in the program below.

Import programMAB_Waveforms_B

A sawtooth waveform generator using analog output, with smoothness setting over potentiometer.

Last commit 18 Dec 2014 by TVZ Mechatronics Team

Exercise 3: Analog communication between two mbeds

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