Conditionals

Lightning review of the last lesson!

• If you cover a sensor, it is triggered. Its value will be 1, which is true.
• If you don’t cover a sensor, it is untriggered. Its value will be 0, which is false.
• An if statement usually looks something like this:

if (condition) {
    Statement;
}

• If the condition in the if statement is true, then the statement will be performed. If not, the program will just move on to the next line of code.
• You can create if statements using equations, like x=10or y<=7.

There might be times when an equation isn’t enough and you would rather have different conditions to work with. Luckily, the possibilities with Arduino are endless! Here are a few more operators that you can use:

&&  //And
||  //Or
!   //Not

Here are some examples!

Example 1:

int x = 10;
int A = 0;

if(x > 5 && x < 9){
    A = 1;
}

int x = 10;
int A = 0;

if(x > 5 || x < 9){
    A = 1;
}

int x = true;
int y = false;
int z = true;
int A = 0;

if(x && !y && z){
    A = 1;
}

If statements are great, but there may be times when you want your program to do one thing if the condition is true and a completely different thing if the condition is false. For those times, you can use else if and else statements! Just like if statements, else if statements have conditions that must be true in order for the statement to be performed. Else statements do not. We’ll get to that soon.

Things to remember:

• Each condition is checked one at a time from top to bottom. If a condition is true, that statement will be executed, and if not, the next condition will be checked.
• Else statements can be used at the end of the program for what happens if none of the conditions are true. You do not need to use an else statement!
• You can use only one if statement and only one else statement, but you can use as many else if statements as you want.

This is what a code with all three types of conditionals look like, using a real-world decision:

if (it is sunny and warm outside){
    I will wear sunscreen;
}

else if(it is sunny and cold outside){ 
    I will wear a jacket; 
}

else{ 
    I will stay inside; 
}

The good thing about using an if-else if chain statement is that your program can only go through one statement at a time, which prevents a lot of confusion.

Example 1:

int x = 5;
int A = 0;

if(x <8){
    A = 1;
}

if(x < 10){
    A = 2;
}

Pseudocode:

• Variable x is set to 5.
• Variable A is set to 0.
• If x is less than 8, A is set to 1.
• If x is less than 10, A is set to 2.
• Since x is 5 and is less than 8, A is set to 1.
• Since x is 5 and is less than 10, A is set to 2.

That can get confusing and might not be what you wanted to happen! (But if you did, that’s OK too!) An if-else if chain would help out in this situation.

Example 2:

int x = 5;
int A = 0;

if(x <8){
    A = 1;
}

else if(
x < 10){
    A = 2;
}

int x = true;
int y = false;
int z = true;
int A = 0;

if(x && y && z){
A = 1;
}

else if(!x && !y && z){
A = 2;
}

else {
A = 3;
}

Now that you know about condition operators, as well as else if and else statements, you can program IR sensors 11, 14, and 18 to help your CoDrone fly!

The first thing you need to do is set up your sensors within void loop so they can constantly check if something is in front of them.

#include <CoDrone.h>

void setup(){
   CoDrone.begin(115200); 
   CoDrone.pair();
 }
void loop(){
   byte bt8 = digitalRead(18);
   byte bt4 = digitalRead(14);
   byte bt1 = digitalRead(11);
}

Next, you are going to include an if statement for sensors 14 and 18 and an else if statement for sensors 11 and 14.

#include <CoDrone.h>

void setup(){
 CoDrone.begin(115200);
 CoDrone.pair();
 }

void loop(){
   byte bt8 = digitalRead(18);
   byte bt4 = digitalRead(14); 
   byte bt1 = digitalRead(11);
  
 if(!bt1 && bt4 && bt8){   
  //Statement 1  
 } 

  else if(bt1 && bt4 && !bt8){ 
  //Statement 2   
 }

}

This is the pseudocode:

• Include the CoDrone library.
• Begin connection at a baud rate of 115200.
• Connect to a nearby drone.
• Check the values of sensors 18, 14, and 11.
• If sensor 11 is untriggered, but sensors 14 and 18 are triggered, Statement 1 will be performed.
• Else, if sensors 11 and 14 are triggered, but sensor 18 is untriggered, Statement 2 will be performed.

Now you can add statements that will be performed if the conditions are true!

#include <CoDrone.h>

void setup(){ 
  CoDrone.begin(115200);
  CoDrone.pair();

  CoDrone.takeoff();
 }

void loop(){
  byte bt8 = digitalRead(18); 
  byte bt4 = digitalRead(14); 
  byte bt1 = digitalRead(11); 

  // If pin 18 is covered, pitch forward for 2 seconds
  if(!bt1 && !bt4 && bt8){ 
    CoDrone.setPitch(70);
    CoDrone.move(2);
  } 

else if(bt1 && bt4 && !bt8){
     CoDrone.emergencyStop();   
    }
}

Challenge: Joyride

Using what your learned in this lesson, write a flight controller for your CoDrone!

Rules:

• You can only use the IR sensors on your remote control.
• No joysticks are allowed!
• You have to include a kill switch.

Hints:

• To take off using throttle, your throttle’s value should be set to 60 or above.
• To move sideways, you can just use roll, or you can use yaw to turn and pitch to go forward.
• You can use combinations to make more flight movements!