🔦 Level 2 – Sensors & IR Control
Project 2.4: "Musical Touch Sensor"
Project 2.4 – Musical Touch Sensor
🎯 What you’ll learn
- Detect touch input using the TTP223 sensor.
- Play notes on a buzzer.
- Map touches to different sounds or patterns.
- Build a simple musical instrument.
🧱 Blocks glossary used
pinX = machine.Pin(X, machine.Pin.IN)→ Setup touch input.pinX.value()→ Read touch state (0 or 1).midi = music.MIDI(pin)→ Setup buzzer output.midi.pitch_time(freq, ms)→ Play a note at frequency for duration.time.sleep()→ Delay.while True:→ Infinite loop.
🧰 What you need
- D1 R32 board.
- TTP223 touch sensor (Pin 2).
- Buzzer (Pin 26).
✅ Before you start
print("Ready!") # Confirm serial monitor works
🎮 Microprojects
🎮 Microproject 2.4.1 – Simple contact detection
Idea: Detect touch and print state.
Pins: Touch=2.
# Simple contact detection
import machine, time # Import pin control and time
pin2 = machine.Pin(2, machine.Pin.IN) # Touch sensor input on pin 2
print("Touch detection ready") # Serial start message
while True: # Infinite loop
state = pin2.value() # Read sensor state (0 or 1)
print("Touch state:", state) # Print state
time.sleep(0.2) # Delay for stability
- Reflection: You can see the sensor change from 0 to 1 when touched.
- Challenge: Add an LED on pin 5 that turns ON when touched.
🎮 Microproject 2.4.2 – Different notes per tap
Idea: Touch plays a single note.
Pins: Touch=2, Buzzer=26.
# Different notes per tap
import machine, time, music # Import pin control, time, and music
pin2 = machine.Pin(2, machine.Pin.IN) # Touch sensor input
midi = music.MIDI(26) # Buzzer output on pin 26
print("Touch notes ready")
while True:
if pin2.value() == 1: # If touch detected
midi.pitch_time(440, 200) # Play A4 (440 Hz) for 200 ms
print("Note A4 played") # Serial confirmation
time.sleep(0.3) # Prevent multiple triggers
time.sleep(0.05) # Fast scan delay
- Reflection: A single touch produces a clear note.
- Challenge: Add button logic: first touch plays A4, second touch plays C5.
🎮 Microproject 2.4.3 – Simple piano 4 notes
Idea: Touch plays a short scale (C, D, E, F).
Pins: Touch=2, Buzzer=26.
# Simple piano 4 notes
import machine, time, music
pin2 = machine.Pin(2, machine.Pin.IN) # Touch sensor input
midi = music.MIDI(26) # Buzzer output
print("4-note piano ready")
while True:
if pin2.value() == 1: # If touch detected
midi.pitch_time(262, 200) # C4
time.sleep(0.05)
midi.pitch_time(294, 200) # D4
time.sleep(0.05)
midi.pitch_time(330, 200) # E4
time.sleep(0.05)
midi.pitch_time(349, 200) # F4
print("4-note sequence played")
time.sleep(0.3) # Prevent repeat
time.sleep(0.05)
- Reflection: A touch triggers a mini piano scale.
- Challenge: Add G4 to extend the scale.
🎮 Microproject 2.4.4 – Tactile rhythmic pattern
Idea: Touch plays a rhythm (ta‑ta‑taa).
Pins: Touch=2, Buzzer=26.
# Tactile rhythmic pattern
import machine, time, music
pin2 = machine.Pin(2, machine.Pin.IN) # Touch sensor
midi = music.MIDI(26) # Buzzer
print("Rhythm pattern ready")
while True:
if pin2.value() == 1: # If touch detected
midi.pitch_time(440, 150) # Short note
time.sleep(0.1)
midi.pitch_time(440, 150) # Short note
time.sleep(0.1)
midi.pitch_time(440, 400) # Long note
print("Pattern ta-ta-taa")
time.sleep(0.3) # Prevent repeat
time.sleep(0.05)
- Reflection: A single touch plays a rhythm with short and long notes.
- Challenge: Add a second rhythm pattern triggered by a second touch.
🎮 Microproject 2.4.5 – Complete musical instrument
Idea: Touch alternates between note mode and rhythm mode.
Pins: Touch=2, Buzzer=26.
# Complete musical instrument
import machine, time, music
pin2 = machine.Pin(2, machine.Pin.IN) # Touch sensor input
midi = music.MIDI(26) # Buzzer output
mode = 0 # Mode variable (0=notes, 1=rhythm)
print("Instrument ready (mode 0)")
while True:
if pin2.value() == 1: # If touch detected
mode = 1 - mode # Toggle mode
print("Mode changed:", mode)
if mode == 0: # Note mode
midi.pitch_time(262, 200) # C4
time.sleep(0.05)
midi.pitch_time(330, 200) # E4
time.sleep(0.05)
midi.pitch_time(392, 200) # G4
print("Note mode sequence")
else: # Rhythm mode
midi.pitch_time(440, 150) # Short note
time.sleep(0.1)
midi.pitch_time(440, 150) # Short note
time.sleep(0.1)
midi.pitch_time(440, 400) # Long note
print("Rhythm mode pattern")
time.sleep(0.3) # Prevent repeat
time.sleep(0.05)
- Reflection: The instrument now has two modes controlled by touch.
- Challenge: Add a third mode for a longer melody.
✨ Main Project – Musical Touch Sensor
🔧 Blocks steps
- Touch input: Detect contact with
pin2.value(). - Music output: Play notes with
music.MIDIandpitch_time. - Logic: Switch between modes (notes vs rhythm).
- Serial: Print feedback for clarity.
🐍 MicroPython code (line‑by‑line comments)
# Project 2.4 – Musical Touch Sensor (Main Project)
import machine, time, music # Import pin control, time delays, and music library
pin2 = machine.Pin(2, machine.Pin.IN) # Setup touch sensor input on pin 2
midi = music.MIDI(26) # Setup buzzer output on pin 26 using MIDI
mode = 0 # Mode variable: 0 = notes, 1 = rhythm
print("Musical Touch Main ready (mode 0)") # Serial start message
while True: # Infinite loop
if pin2.value() == 1: # If touch detected (sensor returns 1)
mode = 1 - mode # Toggle mode (switch between 0 and 1)
print("Mode changed:", mode) # Print current mode
if mode == 0: # If mode is 0 (notes)
midi.pitch_time(262, 200) # Play C4 for 200 ms
time.sleep(0.05) # Short pause
midi.pitch_time(330, 200) # Play E4 for 200 ms
time.sleep(0.05) # Short pause
midi.pitch_time(392, 200) # Play G4 for 200 ms
print("Note mode sequence played")# Serial confirmation
else: # If mode is 1 (rhythm)
midi.pitch_time(440, 150) # Short note (ta)
time.sleep(0.1) # Short pause
midi.pitch_time(440, 150) # Short note (ta)
time.sleep(0.1) # Short pause
midi.pitch_time(440, 400) # Long note (taa)
print("Rhythm mode pattern played") # Serial confirmation
time.sleep(0.3) # Delay to prevent multiple triggers from one touch
time.sleep(0.05) # Fast scan delay
- Reflection: The program now lets you switch between two musical modes with a single touch.
- Challenge: Add a third mode (mode=2) that plays a longer melody, for example C4–D4–E4–F4–G4.
🕵️ Debugging
🐞 Debugging 2.4.A – False tactile positives
- Symptom: Touch detected even when you don’t press the sensor.
- Cause: Electrical noise or high sensitivity.
- Fix: Add a small delay or debounce logic.
time.sleep(0.1) # Increase delay to filter out false signals
- Why it works: Slower scanning reduces false positives caused by noise.
🐞 Debugging 2.4.B – Notes do not respond
- Symptom: No sound when touched.
- Cause: Wrong pin or missing ground connection.
- Fix:
midi = music.MIDI(26) # Confirm buzzer is wired to pin 26
# Check that sensor, buzzer, and board share the same ground
- Why it works: Correct wiring and shared ground ensure the buzzer receives signals.
✅ Final checklist
- Touch input works with
Pin(2, IN). - Notes play correctly in mode 0.
- Rhythm pattern plays in mode 1.
- Mode toggle works with each touch.
- Serial feedback prints clear messages.
📚 Extras
- Student tip: Try different frequencies (e.g., 523 Hz for C5) to explore higher notes.
- Instructor tip: Show how timing changes rhythm feel.
- Glossary: Touch input, debounce, pitch, mode toggle.
- Mini tip: If sensor outputs inverted values, adjust logic to check for
0instead of1.