Teacher guide Researching & planning ≈ 110 min

Lesson 2 · Weeks 1–2

First code — Blink, the IDE & binary

Open this lesson's deck What students see Speaker-notes view

Learning intention

Write, upload and modify your first Arduino sketch — make the on-board LED blink, explain each line, and modify it to meet a series of challenges.

Success criteria

I can upload _01_Blink.ino and explain what each line does.
I can write pseudocode for the Blink program in plain English.
I can modify the sketch to change the on-time, change the off-time and run two LEDs in patterns.
I can identify and fix at least one syntax error in my own code.

Before class

Open the Blink sketch at /code/<short-id> and add it to your bookmarks bar.
Open the PRP 1 student page in another tab — that's what students follow today.
Open the slide deck: /curriculum/crack-the-code/present/2 (?notes=1 for speaker notes).
Plug in your demo board and verify uploading works before the bell.
Have a small batch of spare USB cables ready (one in six fails).

Materials

Class set of Arduino Uno + MAAS ThinkerShield + USB cable · projector showing the PRP 1 student page or the Arduino IDE · spare USB cables · pin-map reference cards (printable from the resources view).

Demo & teacher script

Demo the finished product — play your prebuilt alarm project and let students hear the buzzer.
Live-code Blink with the class watching: type pinMode(12, OUTPUT);, then void loop() { … }, then upload. Make the D12 LED flash.
Trace one cycle out loud: "now the program sets pin 12 high; LED on; wait 1000 ms; pin 12 low; LED off; wait 1000 ms; …"
Deliberately introduce a bug — delete a semicolon, hit Verify, point out the red error. Then fix it. Students will miss semicolons; this prepares them.
Set them off on the PRP 1 student activity; circulate.

Activities in this lesson

PRP 1

Digital output — Blink

Students will: Write and modify your first Arduino program. Make the D12 LED blink and explain what every line does.

_01_Blink.ino · Blink — PRP #01 (Crack the Code) ✦ English View Raw

void setup() {              // runs once when you press reset or power the board
  pinMode(12, OUTPUT);      // make digital pin 12 an output
}

void loop() {               // runs over and over again, forever
  digitalWrite(12, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);              // wait for one second (1000 milliseconds)
  digitalWrite(12, LOW);    // turn the LED off (LOW)
  delay(1000);              // wait for one second
}

Student activity

Common errors & fixes

"It says error so my code is broken" — usually it's one missing ; or }. Look at the line ABOVE the red one.
"Why isn't my LED working?" — wrong pin (sketches use 12, not 13), wrong board/port, USB cable not fully seated.
"It compiled but nothing happens" — did you press Upload (→), not just Verify (✓)? They're different buttons.

Common misconceptions & fixes

Forgot the semicolon — by far the most common error. The IDE underlines the next line; train students to look up one line.
Wrong board / wrong port in Tools — re-check every lesson.
Pin 12 vs pin 13 — the on-board Arduino LED is pin 13 but the ThinkerShield uses pin 13 for data-transmission indication; the sketches use pin 12 so the LED behaviour is unambiguous.
Camel case — pinmode ≠ pinMode. Tell students "if the colour doesn't change, the spelling is wrong."
Missing closing brace — for every { there must be a }. Put the cursor on a brace; the IDE highlights its partner.

Evidence to collect

Screenshot of the working Blink upload showing "Done uploading" in the IDE (formative).
Annotated code — each line commented in plain English by the student (formative).
IPO chart for Blink in the workbook (formative).
Challenge completion checklist — partner/teacher signs off the four PRP 1 challenges (summative-ish).
Reflection response to the exit prompt (formative).

Support path

Provide a partially-completed Blink sketch with comments already in place — students change only the delay numbers.
Pair-program: one student types, the other reads the line aloud.
Print a labelled pin diagram of the ThinkerShield in large format.

Extension path

Make the LEDs chase in a back-and-forth pattern, not just one direction.
Use the int command to give each pin a friendly name; refactor your sketch to use those names everywhere.
Replace delay() with millis() so the LED can flash without freezing the program (preview of PRP 4).

Exit reflection

Write two sentences in your workbook:

"The hardest part of today's PRP was ____ because ____."
"Next lesson I want to try ____."

Syllabus outcomes hit by this lesson: TE4-4DP TE4-7DI TE4-DES-01 TE4-DIG-02