Day 03: I'm worried about your battery levels

What You'll Learn

By the end of today's mission, you'll have transformed your power-hungry emergency light into an intelligent, switch-controlled system. You'll master the art of reading input signals from the physical world and making your microcontroller respond with precise output control.

When you finish this lesson, you'll be able to:

• Wire a DIP switch as an input device that talks to your HERO Board
• Use digitalRead() to listen for switch positions (ON/OFF, HIGH/LOW)
• Write conditional logic with if and else statements
• Control LED output based on real-world input switches
• Understand the difference between assignment (=) and comparison (==) operators
• Build a complete input-processing-output system that conserves battery power

Most importantly, you'll understand how microcontrollers make decisions—reading the world around them and responding intelligently to changing conditions.

Understanding Input and Output

Think of your microcontroller as the brain of a very attentive robot. Just like you use your senses to understand the world—your eyes see light, your fingers feel texture, your ears hear sounds—a microcontroller uses its pins to "sense" the electrical world around it.

Inputs are like the microcontroller's senses. When you flip a switch, press a button, or a sensor detects motion, these devices send electrical signals to input pins. The microcontroller "reads" these signals and says, "Aha! Something in the world has changed!" It's exactly like when you hear a doorbell and know someone wants to come in.

Outputs are like the microcontroller's actions. Just as you might turn on a light when you hear that doorbell, the microcontroller can send signals to output pins to control LEDs, motors, buzzers, or any other device. It's the microcontroller saying, "Based on what I sensed, here's what I'm going to do about it."

In your survival situation, the DIP switch becomes your way of communicating with the lander's computer. When you flip that switch to ON, you're sending a HIGH signal (about 5 volts) to an input pin. When you flip it OFF, you're sending a LOW signal (0 volts). The microcontroller constantly checks that input pin, asking "What's the human telling me to do right now?"

This input-processing-output cycle happens incredibly fast—thousands of times per second. Your microcontroller is like an extremely dedicated assistant, constantly asking "What should I do? What should I do? What should I do?" and responding immediately to any changes in the input signals.

Today's project demonstrates this beautifully: your switch position (input) gets read by the microcontroller (processing), which then decides whether to turn the LED on or off (output). It's a complete feedback loop between human intention and electronic response.

Code Walkthrough: Building Intelligence

Now comes the moment where your lander's computer brain learns to make decisions. We'll build this intelligence step by step, teaching your microcontroller to listen for your commands and respond appropriately.

Step 1: Including the HERO Board Libraries

#include "Arduino.h"