Arduino Programming, 9 weeks

Blink: the first program

Two wires from an Uno to an LED, then setup(), loop(), pinMode, digitalWrite and delay.

Learning objectives: students will be able to

• Name what setup() and loop() are for
• Set a pin as an output and drive it high and low
• Change a delay and predict the blink rate

Lesson plan

1. Warm up (5 min): run First blink. Read the sketch aloud, line by line.
2. Lesson (15 min): Make it blink with an Uno. Students wire it themselves.
3. Lesson (20 min): Blink: the first program. Change the timing and fix a compile error on purpose.
4. Close (5 min): write the blink pattern for SOS in plain English.

Ask the class

• What happens if you leave out pinMode(13, OUTPUT)?
• How many times a second does the pin change if the LED blinks five times a second?

Graded work

• Make it blink with an Uno: a lesson whose 4 steps tick against the running circuit. Assign it from your class page under A lesson.
• Blink: the first program: a lesson whose 5 steps tick against the running circuit. Assign it from your class page under A lesson.
• Rebuild First blink on your own breadboard, wired from pin 13, and hand it in. Assign First blink as a template and add these checks. Our own build passes every one:
• Check: Pin 13 blinks once a second (pin 13 on uno1 toggles every 1 s, within 50 ms, watched for 4 s).
• Check: The LED lights (the LED led1 is lit at 250 ms).

Projects to open: First blink

Vocabulary

Sketch

An Arduino program.

setup()

Runs once when the board starts.

loop()

Runs over and over, forever, after setup().

Output pin

A pin the program drives high (5 V) or low (0 V).

Standards: 2-AP-12, 2-CS-02

More outputs, in order

Two lamps taking turns, then a traffic light sequence.

Learning objectives: students will be able to

• Drive several outputs from one program
• Write a sequence as steps with timing
• Read a sequence from serial output to debug it

Lesson plan

1. Warm up (5 min): what order do traffic lights go in? Write it as a list.
2. Lesson (20 min): Two outputs, taking turns.
3. Lesson (20 min): Five outputs and a sequence, the pelican crossing.
4. Close (5 min): flowchart the crossing on paper.

Ask the class

• Why does the WAIT lamp light instantly, even while the sketch is inside a long delay?
• With three pins and shift registers, how could you drive many more lamps?

Graded work

• Two outputs, taking turns: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Five outputs and a sequence: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.

Projects to open: Traffic light

Vocabulary

Sequence

Steps that happen in a set order.

Flowchart

A drawing of a program’s steps and decisions.

delay()

Stops the program for a number of milliseconds.

Millisecond

One thousandth of a second.

Standards: 2-AP-10, 2-AP-12

Inputs: buttons and pull-ups

Reading a pin, why pressed reads low, and turning a press into a toggle.

Learning objectives: students will be able to

• Read a button with digitalRead and INPUT_PULLUP
• Explain why an input must never float
• Tell a level from an edge, and debounce a press

Lesson plan

1. Warm up (5 min): open Button and LED. Hold the button. Why does it read LOW?
2. Lesson (20 min): Reading a pin, and the pull-up.
3. Lesson (20 min): Press once for on, once for off.
4. Close (5 min): explain bounce in one sentence.

Ask the class

• Why does the button read LOW when it is pressed?
• Why can one press of a real button be counted several times?

Graded work

• Reading a pin, and the pull-up: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Press once for on, once for off: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Rebuild Button and LED: a button on pin 2 to ground, an LED on pin 13. Hand it in. Assign Button and LED as a template and add these checks. Our own build passes every one:
• Check: The LED is off before anyone presses (pin 13 on uno1 reads LOW at 400 ms).
• Check: The LED goes out again when the button is let go (after pb1 is pressed at 500 ms for 300 ms: pin 13 on uno1 reads LOW at 1100 ms, by 1100 ms).

Projects to open: Button and LED

Vocabulary

Input pin

A pin the program reads as high or low.

Pull-up resistor

A resistor that holds an input high when nothing pulls it low.

Floating

An input connected to nothing, which reads at random.

Debounce

Ignoring the extra edges a mechanical switch makes.

Standards: 2-CS-02, 2-AP-12

Variables, decisions and loops

The C++ underneath: types and sizes, if and else, and a loop over a list.

Learning objectives: students will be able to

• Create variables with suitable types and clear names
• Write an if and else that decides from a value
• Loop over a list with for

Lesson plan

1. Warm up (5 min): what is the biggest number a byte can hold?
2. Lesson (15 min): Variables have a size.
3. Lesson (15 min): One branch runs.
4. Lesson (15 min): A loop over a list.

Ask the class

• What happens when a byte variable holding 255 has 1 added to it?
• Why does only one branch of an if and else ever run?

Graded work

• Variables have a size: a lesson whose 7 steps tick against the running circuit. Assign it from your class page under A lesson.
• One branch runs: a lesson whose 7 steps tick against the running circuit. Assign it from your class page under A lesson.
• A loop over a list: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.

Vocabulary

Variable

A named place that holds a value.

Type

What kind of value a variable holds, and how big it can be.

Condition

A test that is true or false.

for loop

Repeats a block a counted number of times.

Standards: 2-AP-11, 2-AP-12

Timing without delay

Ask the time instead of waiting for it: two rates at once, and a board that still listens.

Learning objectives: students will be able to

• Use millis() to run two things at different rates
• Explain why delay() makes a program unresponsive
• Keep a timestamp for each thing that repeats

Lesson plan

1. Warm up (5 min): try to blink two LEDs at different rates with delay alone.
2. Lesson (20 min): Two rates at once, without delay.
3. Lesson (20 min): Blinking and listening at the same time.
4. Close (5 min): name one real device that must never block.

Ask the class

• Why can delay() not blink two LEDs at two different rates?
• Why does millis() keep counting while a delay() is running?

Graded work

• Two rates at once, without delay: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Blinking and listening at the same time: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.

Vocabulary

millis()

Milliseconds since the board started.

Blocking

Code that stops everything else while it waits.

Timestamp

A saved time, to compare against later.

Responsive

Reacting to input quickly.

Standards: 2-AP-12, 2-AP-17

Analog input

A voltage becomes a number from 0 to 1023, and a program decides from it.

Learning objectives: students will be able to

• Read a voltage with analogRead and convert it to millivolts
• Use a threshold to make a decision from a reading
• Explain hysteresis with an everyday example

Lesson plan

1. Warm up (5 min): open Read a knob. Turn it and watch the numbers.
2. Lesson (20 min): Reading a voltage.
3. Lesson (20 min): Deciding from a reading, the night light.
4. Close (5 min): what is one count worth, in millivolts?

Ask the class

• On a 5 V Uno, about how many millivolts is one count of analogRead?
• Why does a thermostat not switch on and off at exactly the same temperature?

Graded work

• Reading a voltage: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Deciding from a reading: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Rebuild Read a knob: a potentiometer across 5 V and ground with its wiper on A0. Hand it in. Assign Read a knob as a template and add these checks. Our own build passes every one:
• Check: The monitor prints the A0 reading (the serial monitor prints a line matching /A0 = \d+/ within 1500 ms).

Projects to open: Read a knob · Night light

Vocabulary

Analog

A value that can be anything in a range, not just on or off.

ADC

Analog-to-digital converter: turns a voltage into a number.

Threshold

The value where a decision changes.

Hysteresis

Two thresholds, one going up and one going down, to stop flickering.

Standards: 2-CS-02, 2-DA-08

PWM, light and sound

Brightness from a digital pin, a breathing LED and a melody on a piezo.

Learning objectives: students will be able to

• Define duty cycle and relate it to brightness
• Use analogWrite on a PWM pin
• Play notes with tone() and noTone() from a list

Lesson plan

1. Warm up (5 min): run Fade an LED. How does a digital pin make in-between brightness?
2. Lesson (20 min): Brightness from a digital pin.
3. Build (20 min): open Piezo melody and rewrite the tune.
4. Close (5 min): what does a 25 percent duty cycle average to on 5 V?

Ask the class

• What average voltage does a 25 percent duty cycle give on a 5 V pin?
• In Piezo melody, why is there a short gap after every note?

Graded work

• Brightness from a digital pin: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Rebuild Fade an LED: an LED and 220 ohm resistor on pin 9, breathing with analogWrite. Hand it in. Assign Fade an LED as a template and add these checks. Our own build passes every one:
• Check: Pin 9 switches at the Uno’s PWM rate (pin 9 on uno1 carries PWM at 490 Hz, within 20 Hz).

Projects to open: Fade an LED · Piezo melody · RGB color mixer

Vocabulary

PWM

Pulse width modulation: switching fast so the average sets the level.

Duty cycle

The percentage of time a pin is high.

Frequency

How many times a second something repeats, in hertz.

Piezo

A small speaker that clicks with each voltage change.

Standards: 2-AP-12, 2-AP-16

Serial and functions

Printing to the monitor, taking commands, and writing a function once.

Learning objectives: students will be able to

• Print values to the serial monitor and read characters back
• Act on a typed command
• Write a function with parameters and call it

Lesson plan

1. Warm up (5 min): what would you want a board to tell you while it runs?
2. Lesson (15 min): Making the board talk.
3. Lesson (15 min): Taking commands.
4. Lesson (15 min): Write it once, a function.

Ask the class

• Why does printing a long line take real time at a given baud rate?
• What makes a function with parameters easier to reuse than copied code?

Graded work

• Making the board talk: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Taking commands: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Write it once: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.

Projects to open: Reaction timer

Vocabulary

Serial monitor

A window that shows what the board prints, and sends what you type.

Baud rate

How many bits a second a serial line carries.

Function

A named block of code you can call.

Parameter

A value handed to a function when it is called.

Standards: 2-AP-14, 2-CS-02

Final project

Plan a build as inputs, processing and outputs, build it, test it, and present it as a link.

Learning objectives: students will be able to

• Plan a project as inputs, processing and outputs before wiring
• Use one variable to track what state a program is in
• Test a project against its own requirements and refine it

Lesson plan

1. Plan (1 period): pick a brief (a reaction game, a metronome, a night light that fades, or their own) and list inputs, processing and outputs.
2. Lesson (1 period): One variable that says where you are, the state machine.
3. Build and test (2 to 3 periods): build it, write three tests it must pass, and fix what fails.
4. Present (1 period): a two-minute demo from the shared link.

Ask the class

• What states does your project have, and what moves it from one to the next?
• Which of your tests failed first, and what did you change?

Graded work

• One variable that says where you are: a lesson whose 8 steps tick against the running circuit. Assign it from your class page under A lesson.
• Project: a reaction timer: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.
• Project: a metronome: a lesson whose 6 steps tick against the running circuit. Assign it from your class page under A lesson.

Projects to open: Reaction timer · Metronome · Electronic dice

Vocabulary

State machine

A program that is always in one named state, with rules for moving between them.

Requirement

Something the finished project must do.

Test case

A specific input and the result it should give.

Iteration

Improving a design by testing and changing it again.

Standards: 3A-AP-13, 3A-AP-17, 2-AP-17, 2-AP-15