Tricycle Tank WEB EDITION

💡 The big idea in plain words

A robot is a computer with hands. This tank's "brain" is a set of behaviours that switch: drive, aim, reload, play a melody. At every heartbeat (10 ms) the code checks a few conditions — "did the player move the stick?", "did we get hit?", "is the magazine empty?" — and reacts. That pattern, a finite-state machine, is the whole secret of the project: complex behaviour from simple, well-defined states and crisp transition rules.

🧠 Finite-state machines (FSM)

A finite-state machine is a flowchart the program actually lives inside: exactly one state is active at a time, and every arrow between states has a condition. Formally,

\[ \delta : S \times I \rightarrow S \]

— a transition function mapping (current state, input event) to the next state. The C code runs four parallel FSMs on a shared 10 ms clock:

• xbox360 — controller input, debounced;
• player — melody playback on the buzzer (Despacito, GoT, Tetris, Star Wars);
• ruedas — wheel PWM + steering;
• torreta — turret servos, IR shot, shoot timeout.

The web edition ports these states and timings 1:1 — the game you play is the C program's behaviour, rendered in the browser.

⚡ PWM — how you control a motor with 0s and 1s

A digital pin can only be fully on or fully off. PWM (pulse width modulation) fakes "in between" by switching very fast:

\[ \text{duty} = \frac{t_{\text{on}}}{T} \times 100\% \]

The duty cycle — fraction of time the pin is high — sets the effective voltage, i.e. the motor speed. The wheels use hardware PWM (pins 18/19: precise, no CPU involvement); the turret servos use software PWM (pins 17/27), where the pulse width itself encodes the angle (e.g. 1 ms ≈ 0°, 1.5 ms ≈ 90°, 2 ms ≈ 180°).

🖱️ Debouncing — one press should mean one event

Mechanical buttons "bounce": the contacts chatter for a few milliseconds before settling. Without care, one press looks like many. The fix is a debounce window — ignore readings until the signal has been stable for a few ms — so exactly one event fires per press.

🎯 IR "laser" hit detection

The laser is infrared light; the receiver raises a hardware interrupt (pin 11, rising edge) the moment a hit arrives. The controller counts magazine rounds (10 shots, reload with X) and applies damage to the opponent's HP.