Session 6: Code Your Robot

Goal: Use everything you learned in Sessions 1–3 — micro:bit programming, IR sensor logic, and motor control — to write a MakeCode program that makes your completed robot chassis move, turn, and respond to the world around it.

Putting It All Together

In the first three sessions you built up three core skills:

Session What You Learned How You’ll Use It Today
Session 1 micro:bit basics — MakeCode, LEDs, buttons, variables Program structure, button controls, display feedback
Session 2 IR sensors — wiring, digital readings, conditional logic Obstacle detection to stop or turn the robot
Session 3 Motors — L298N driver, PWM speed control, differential drive Drive the robot forward, backward, and turn

Today all three come together in one robot program.

Part 1: Review Your Motor Setup

Your robot now uses the Motor:bit Breakout Board instead of the L298N from Session 3. The pin mapping is the same:

Function Pin in code What it controls
Motor M1 direction A digital write pin P1 Left motor direction
Motor M2 direction B digital write pin P2 Right motor direction
Speed (both motors) analog write pin P0 0 = stop, 1023 = full speed

If a wheel spins the wrong direction when you test, swap the 1 and 0 values for that motor’s direction pin.

Part 2: Write Your Drive Program

Open MakeCode and create a new project called My Robot.

Step 1: Create helper functions

Use the Make a Function block (under Advanced → Functions) to create reusable move commands:

moveForward

  • digital write pin P1 to 1
  • digital write pin P2 to 1
  • analog write pin P0 to 600

moveBackward

  • digital write pin P1 to 0
  • digital write pin P2 to 0
  • analog write pin P0 to 600

turnLeft

  • digital write pin P1 to 0
  • digital write pin P2 to 1
  • analog write pin P0 to 600

turnRight

  • digital write pin P1 to 1
  • digital write pin P2 to 0
  • analog write pin P0 to 600

stopRobot

  • analog write pin P0 to 0

Step 2: Basic button controls

Wire up button A and B (from Session 1) to your new functions:

  • on button A pressed → call moveForward
  • on button B pressed → call stopRobot
  • on button A+B pressed → call turnLeft

Test this first — download the program, turn on the battery pack, and press the buttons to confirm each motor behaves as expected.

Step 3: Add IR sensor obstacle detection

Connect your IR sensor (from Session 2) to pin P8 (or the same pin you used in Session 2).

Add a forever loop:

forever:
    if digital read pin P8 = 0:
        stopRobot
        show icon (sad face)
        pause 500 ms
        turnLeft
        pause 400 ms
    else:
        (do nothing / keep current movement)

Recall from Session 2: The IR sensor outputs 0 when it detects an obstacle close in front. Use that same logic here to make the robot stop and turn away automatically.

Step 4: Combine manual and automatic control

A complete robot program lets you start moving with a button and stop automatically when it hits an obstacle:

  • on button A pressed → set a variable driving to true, call moveForward
  • on button B pressed → set driving to false, call stopRobot
  • forever loop:
    • if driving = true and IR sensor reads 0 → stopRobot, show icon, pause, turnLeft, pause, moveForward

Part 3: Test and Tune

Work through these tests in order. Fix one issue before moving to the next.

Test 1 — Straight line

Place the robot on a flat surface. Press A. Does it drive forward in a straight line?

  • If it veers left → reduce the speed on the left motor (lower the P0 value while P1 is active, or swap wires for fine-tuning)
  • If it veers right → adjust the right motor the same way

Test 2 — Turn accuracy

Test turnLeft and turnRight. Does the robot turn roughly 90°?

  • Adjust the pause duration inside the turn functions (shorter pause = smaller turn angle)

Test 3 — Obstacle stop

Hold a book in front of the IR sensor. Does the robot stop and turn away?

  • If not, check your IR sensor wiring from Session 2 and the pin number in your code

Test 4 — Full run

Clear a space on the floor. Start the robot with button A and let it drive. It should stop and turn whenever it detects an obstacle and continue on its own.

Design Challenges

Once your robot passes all four tests, try one or more of these:

A — Speed Ramp Make the robot gradually speed up from 0 to 800 over 1 second using a loop that increases analog write pin P0 in steps of 100.

B — Three-obstacle avoidance If the robot has attempted to turn 3 times in a row without clearing an obstacle, make it drive backward for 1 second before trying again.

C — Figure Eight Program the robot to drive forward for 2 seconds, turn right for 0.5 seconds, and repeat 8 times to trace a figure-eight shape. Tune the timing until the path closes cleanly.

D — Sensor display Show the IR sensor reading live on the micro:bit LED display — a filled square when an obstacle is detected, an empty square when the path is clear.

Key Concepts You Used Today

  • Applying prior knowledge: combining micro:bit, IR sensors, and motors from Sessions 1–3 into a single working system
  • Functions: reusable blocks that make programs easier to read and modify
  • Variables for state: using a driving variable to track whether the robot should be moving
  • Sensor-driven behavior: reading the IR sensor to change the robot’s action automatically
  • Iterative testing: testing each feature in isolation before combining them

Congratulations!

You have designed, built, wired, and programmed a working autonomous robot from scratch. You moved from blinking LEDs in Session 1 all the way to a robot that drives itself and avoids obstacles — great work!

CATALOG