States

If you remember how to write if statements or variables, you’ll be able to create states for the Trailer Bot! For this bot, you’ll need to create states so it can work with a remote control, with a program, and go fast.

The first thing you need to do is create a variable named state so you can keep track of the mode you’re in. However, variables can only hold letters and numbers, so you’ll need to assign each mode a different value. We assigned 0 as fast, autonomous as 1, and remote control as 3.

Finally, create if and else if statements so the program knows which state the Trailer Bot is in.

int state = 0;
 
if (state == 0)
{
  // code for fast mode
}
else if (state == 1)
{
  // code for autonomous mode
}
else if (state == 2)
{
  // code for remote control mode
}

It’s easy to get your states and the numbers that go with them mixed up, especially if you start adding more states. To make your life easier, create variables before your if statements so you can keep track of everything. If you do this, you just need to remember the name of the variable when you need it in your program!

int fast = 0;
int auton = 1;
int remote = 2;
int state = auton;
 
if (state == fast)
{
  // code for fast mode
}
else if (state == auton)
{
  // code for autonomous mode
}
else if (state == remote)
{
  // code for remote control mode
}

This is an example code using states. When this code runs, it will print out a different message on the serial monitor and then wait a certain amount of time depending on the state it’s in.

// state values
int slow = 0;
int medium = 1;
int fast = 2;
int state = fast;
 
void setup()
{
  Serial.begin(9600); // start Serial monitor
}
 
void loop()
{
 if (state == fast) // fast state
 {
   Serial.println("state is fast");
   delay(100); // short delay
 }
 else if (state == medium) // medium state
 {
   Serial.println("state is medium");
   delay(250); // medium delay
 }
 else if (state == slow) // slow state
 {
   Serial.println("state is slow");
   delay(500); // long delay
 }
}

Still not sure about states? Watch the video!