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Program an Ultrasonic Sensor

The true way to get good at something is to PRACTICE. I designed the robotics challenge to help you practice basic skills in an applied way.

This week’s robotics challenge focuses on ultrasonic sensors and will enhance your programming skills by utilizing pre-existing code.

Have a Solution? Share Your Work!

Use #learnrobotics #roboticschallenge in your Facebook, Twitter, or Instagram post! I want these challenges to be as interactive as possible, so if you include #review with your post, I will provide personal feedback on your solution.

Challenge Overview

You’re given 3 ultrasonic sensors and 1 Arduino Uno with necessary wiring used to prevent a 2WD mobile robot from driving into an obstacle. The motor control methods have already been written (and working 😛 ) and can be called using the following commands:

forward(motorName, duration); //forward for the specified motor & duration
backward(motorName, duration); //backward for the specified motor & duration
left(); //90-deg turn left
right(); //90-deg turn right
stop(motorName); //stop motor in current position

Here’s the current hardware configuration of the device.

robotics challenge ultrasonic sensors wiring diagram

Your Task

In this week’s robotics challenge, create a method, int avoidObstacles(int ultrasonicPin, int distance) in an Arduino-C program to prevent the robot from crashing into an obstacle using the ultrasonic sensors. You should be at least 3 inches away from the obstacle while running. You do not need to use all of the sensors. The purpose is to configure them appropriately to solve the issue.

Here’s a template to help you get started on a solution:

/* GLOBAL DEFINITIONS
 * Define your global variables here.
 */
 //left ultrasonic
 const int leftULTRATRIG=3; //pin on Digital port 3
 const int leftULTRAECHO=2;
//right ultrasonic
 //FILL THIS OUT
//center ultrasonic
 //FILL THIS OUT
/* REQUIRED METHOD
 * Configure your pins as inputs or outputs here.
 */
void setup(){
 //*** ultrasonics ***
 //*** motors ***
 //Setup Channel A - Right Side
  pinMode(12, OUTPUT); //Initiates Motor Channel A pin
  pinMode(9, OUTPUT); //Initiates Break Channel A pin
  //Setup Channel B - Left Side
  // FILL THIS OUT
}
/* Input Parameters: const int ultrasonicPin, int inputDistance
* Return Statement: bool
* Determines if the given ultrasonic sensor is within the given distance.
* Returns TRUE if the sensor is <= to input distance * Returns FALSE if the sensor is >= to input distance
* Use case: avoidObstacles(ultrasonicPin, inputDistance)
*/
bool avoidObstacles(const int ultrasonicPin, int inputDistance){
// fill this out
}
// OPTIONAL: Create additional helper methods here.
/* REQUIRED METHOD
* This method is like "main." Loops forever.
* The following comments are things to consider
* when determining your solution.
*/
void loop(){
// CHECK TO SEE IF THERE'S AN OBSTACLE WITHIN 3IN OF THE LEFT SIDE
// BACK UP & TURN IN THE OPPOSITE DIRECTION
// CHECK TO SEE IF THERE'S AN OBSTACLE WITHIN 3IN OF THE RIGHT SIDE
// BACK UP & TURN IN THE OPPOSITE DIRECTION
// CHECK TO SEE IF THERE'S AN OBSTACLE WITHIN 3IN OF CENTER
// BACK UP & TURN LEFT OR RIGHT
}

This template is provided as a GUIDELINE. You do not need to use it in your solution, as there are many ways to solve this problem. It’s there if you need a quick nudge in the right direction. As always, if you’re really stuck, feel free to ask a question below or Tweet Me (@lizmillerfit) for help!

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