Bonus · LED Motor Speedometer¶

Right now your joystick-controlled motor program prints the current speed to the terminal. This bonus project replaces that number with a visual speedometer built from LEDs.

The project is open-ended — there are two approaches, and you pick the one that appeals to you.

Approach A — Threshold speedometer (easier, less precise)¶

Divide the maximum motor speed into 20% chunks. Use 5 LEDs. Light up one more LED for each 20% threshold you cross:

0–20%: 0 LEDs lit
20–40%: 1 LED lit
40–60%: 2 LEDs lit
60–80%: 3 LEDs lit
80–100%: 4 LEDs lit
100%: 5 LEDs lit

This is straightforward with if/else if logic. → Making decisions (if/else)

Approach B — Binary counter (harder, very precise)¶

Use N LEDs to display the motor speed as a binary number. Each LED represents one bit: lit = 1, off = 0. With 9 LEDs you can represent values from 0 to 511 exactly; with 10 LEDs, 0 to 1023.

This approach uses bit shift operators to read each bit of the speed value and translate it to an LED state. → Bit operators

What you need¶

LEDs (ask your instructor how many, based on your chosen approach)
Extra wires to connect each LED to a GPIO pin on the Pi

Setting up the LEDs¶

On the breadboard¶

Insert each LED so that: - The shorter leg (cathode) goes into the blue ground rail - The longer leg (anode) goes into a numbered row

You may need to bend the legs slightly to fit.

Connecting to the Raspberry Pi¶

Run a wire from the numbered row (where the long leg is) to a GPIO pin on the Pi. Any GPIO pin works — look up "Raspberry Pi 5 pinout diagram" to find them. Write down which pin number you use for each LED, because you will need those numbers in your code.

Driving an LED in code¶

There are two steps for each LED:

In setup(): Set the pin mode to OUTPUT.

In loop(): Write HIGH to turn the LED on, LOW to turn it off.

→ pinMode() · digitalWrite()

Try it

Start by getting a single LED working: set its pin mode in setup(), then write HIGH to turn it on. Once that works, add a second LED, then the rest.

For Approach B: bit operators¶

If you chose the binary counter approach, you will need to read individual bits of the speed value. The pattern is:

Bit N of a value is set if (value & (1 << N)) is non-zero.

Look into how that works before you start coding. → Bit operators