🔢 Build a Smart 1-Digit Digital Counter with Raspberry Pi Pico

🎯 Project Goal:

Create a modern 1-digit counter using a 7-segment display, Raspberry Pi Pico, and add smart features like:

• Start & Reset (Home) buttons
• Green & Red LEDs
• Buzzer beep alerts
• Auto-reset when the count ends

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📚 What Will You Learn?

✅ How to use a 7-segment display
✅ How to control LEDs and buzzer
✅ How to connect buttons
✅ How to write a smart logic program in MicroPython

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🧰 Components Needed

Component	Quantity	GPIO Pins Used
Raspberry Pi Pico	1	—
7-Segment Display (Common Cathode)	1	GPIO 0–7
Push Buttons	2	GPIO 10 (Start), GPIO 11 (Home)
Green LED	1	GPIO 18
Red LED	1	GPIO 19
Buzzer (Active or PWM)	1	GPIO 15
220Ω Resistors (for LEDs)	2	—
Breadboard + Jumper Wires	—	—
USB cable + Thonny IDE	1	For programming

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🔌 Circuit Diagram Summary

7-Segment Connections (GPIO 0–7)

Segment	Label	GPIO
a	A	0
b	B	1
c	C	2
d	D	3
e	E	4
f	F	5
g	G	6
dp	DP	7

Other Connections

Device	Connect To
Start Button	GPIO 10 + GND
Home Button	GPIO 11 + GND
Green LED	GPIO 18 (via resistor) + GND
Red LED	GPIO 19 (via resistor) + GND
Buzzer	GPIO 15 + GND (via resistor optional)

⚠️ Use Pin.PULL_DOWN in code to ensure buttons are detected correctly.

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💻 Full MicroPython Code

Upload this code using Thonny IDE:

from machine import Pin, PWM
import utime

# ----- 7-segment segment pins (a to dp) -----
segment_pins = [0, 1, 2, 3, 4, 5, 6, 7]
segments = [Pin(pin, Pin.OUT) for pin in segment_pins]

# ----- LEDs -----
green_led = Pin(18, Pin.OUT)
red_led = Pin(19, Pin.OUT)

# ----- Buzzer -----
buzzer = PWM(Pin(15))

# ----- Buttons -----
start_button = Pin(10, Pin.IN, Pin.PULL_DOWN)
home_button = Pin(11, Pin.IN, Pin.PULL_DOWN)

# ----- 7-segment digit patterns -----
digit_patterns = [
    (1, 1, 1, 1, 1, 1, 0, 0),  # 0
    (0, 1, 1, 0, 0, 0, 0, 0),  # 1
    (1, 1, 0, 1, 1, 0, 1, 0),  # 2
    (1, 1, 1, 1, 0, 0, 1, 0),  # 3
    (0, 1, 1, 0, 0, 1, 1, 0),  # 4
    (1, 0, 1, 1, 0, 1, 1, 0),  # 5
    (1, 0, 1, 1, 1, 1, 1, 0),  # 6
    (1, 1, 1, 0, 0, 0, 0, 0),  # 7
    (1, 1, 1, 1, 1, 1, 1, 0),  # 8
    (1, 1, 1, 1, 0, 1, 1, 0)   # 9
]

# ----- Function to display a digit -----
def display_number(num):
    pattern = digit_patterns[num]
    for seg, val in zip(segments, pattern):
        seg.value(val)

# ----- Function for short beep-beep -----
def beep_short():
    for _ in range(2):
        buzzer.freq(1200)
        buzzer.duty_u16(30000)
        utime.sleep(0.1)
        buzzer.duty_u16(0)
        utime.sleep(0.1)

# ----- Function for long final beep -----
def beep_long():
    buzzer.freq(800)
    buzzer.duty_u16(40000)
    utime.sleep(3)
    buzzer.duty_u16(0)

# ----- Initialize -----
count = 0
state = "idle"
display_number(count)
green_led.value(0)
red_led.value(0)

# ----- Main loop -----
while True:
    # HOME BUTTON → reset to 0
    if home_button.value() == 1:
        count = 0
        state = "idle"
        display_number(count)
        green_led.value(0)
        red_led.value(0)
        buzzer.duty_u16(0)
        utime.sleep(0.3)  # Debounce

    # START BUTTON → begin counting
    if start_button.value() == 1 and state == "idle":
        state = "counting"
        utime.sleep(0.3)  # Debounce

    # COUNTING STATE
    if state == "counting":
        display_number(count)
        green_led.toggle()
        beep_short()
        utime.sleep(1)
        count += 1
        if count > 9:
            count = 9
            state = "done"
            green_led.value(0)

    # DONE STATE → 3s long beep + red LED + auto reset
    if state == "done":
        red_led.value(1)
        beep_long()
        red_led.value(0)
        count = 0
        display_number(count)
        state = "idle"

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🧠 How It Works – Step by Step

1. Home State (count = 0)
   → Red & green LEDs are OFF
   → Display shows “0”
   → Waiting for user to press Start
2. Press Start
   → Starts counting from current number
   → Green LED blinks, buzzer goes beep-beep
   → Increments every 1 second
3. At Number 9
   → Green LED stops
   → Red LED turns ON
   → Buzzer gives a long 3s beep
   → Automatically resets to Home state
4. Press Home Anytime
   → Immediately stops counting
   → Display resets to 0
   → System waits for Start again

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🧠 Code with Line-by-Line Explanation

from machine import Pin, PWM
import utime

✅ Imports Required Modules

• machine: Gives access to hardware pins (GPIO).
• Pin: Used to define input/output pins.
• PWM: Used to control buzzer sound using pulse-width modulation.
• utime: Provides delay functions like sleep().

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# Segment Pins a to dp
segment_pins = [0, 1, 2, 3, 4, 5, 6, 7]
segments = [Pin(pin, Pin.OUT) for pin in segment_pins]

✅ Defines 7-Segment Display Pins

• segment_pins: List of GPIOs connected to segments a to dp (decimal point).
• segments: Creates a list of Pin objects set to OUTPUT mode for each segment.

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# LEDs
green_led = Pin(18, Pin.OUT)
red_led = Pin(19, Pin.OUT)

✅ Sets Up LEDs

• green_led: Blinks during counting.
• red_led: Turns ON when count reaches 9.

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# Buzzer
buzzer = PWM(Pin(15))

✅ Sets Up Buzzer

• Connects PWM (sound signal) to GPIO15.
• This lets you control frequency and duration of beeps.

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# Buttons
start_button = Pin(10, Pin.IN, Pin.PULL_DOWN)
home_button = Pin(11, Pin.IN, Pin.PULL_DOWN)

✅ Sets Up Buttons

• start_button: Starts the counting process.
• home_button: Resets counter to 0 and stops everything.
• Pin.PULL_DOWN: Ensures button reads 0 until pressed (then becomes 1).

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# Segment patterns for 0–9
digit_patterns = [
    (1, 1, 1, 1, 1, 1, 0, 0),  # 0
    (0, 1, 1, 0, 0, 0, 0, 0),  # 1
    (1, 1, 0, 1, 1, 0, 1, 0),  # 2
    (1, 1, 1, 1, 0, 0, 1, 0),  # 3
    (0, 1, 1, 0, 0, 1, 1, 0),  # 4
    (1, 0, 1, 1, 0, 1, 1, 0),  # 5
    (1, 0, 1, 1, 1, 1, 1, 0),  # 6
    (1, 1, 1, 0, 0, 0, 0, 0),  # 7
    (1, 1, 1, 1, 1, 1, 1, 0),  # 8
    (1, 1, 1, 1, 0, 1, 1, 0)   # 9
]

✅ Stores Segment Patterns for Each Digit

• Each tuple represents which segments to turn ON (1) or OFF (0) for numbers 0 to 9.
• The order matches GPIO pins 0 to 7 (a to dp).

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# Display a digit
def display_number(num):
    pattern = digit_patterns[num]
    for seg, val in zip(segments, pattern):
        seg.value(val)

✅ Displays a Number on the 7-Segment

• Looks up the segment pattern for the given num.
• Sets each segment to ON or OFF using seg.value(val).

---

# Short double beep during counting
def beep_short():
    for _ in range(2):
        buzzer.freq(1200)           # Set frequency
        buzzer.duty_u16(30000)      # Set sound volume (duty cycle)
        utime.sleep(0.1)            # Beep for 0.1 seconds
        buzzer.duty_u16(0)          # Stop beep
        utime.sleep(0.1)            # Wait before next beep

✅ Makes “Beep-Beep” Sound While Counting

• Runs 2 short beeps using PWM frequency and duty cycle.

---

# Long beep when count ends
def beep_long():
    buzzer.freq(800)                # Lower frequency for final beep
    buzzer.duty_u16(40000)          # Louder sound
    utime.sleep(3)                  # Hold for 3 seconds
    buzzer.duty_u16(0)              # Turn off buzzer

✅ Final Long Beep When Count Ends at 9

• Buzzer gives a continuous beep for 3 seconds.

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# Initial state
count = 0
state = "idle"
display_number(count)

✅ Sets Up Initial State

• count = 0: Starting number.
• state = "idle": System is waiting for the start button.
• display_number(count): Show 0 on the display.

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# Main loop
while True:

✅ Infinite Loop Keeps Running the Program

• Continuously checks button inputs and updates the system.

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if home_button.value() == 1:
        count = 0
        state = "idle"
        display_number(count)
        green_led.value(0)
        red_led.value(0)
        buzzer.duty_u16(0)
        utime.sleep(0.3)

✅ Home Button Logic

• Resets everything to the home state.
• Green & red LEDs OFF, buzzer OFF, display reset to 0.

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   if start_button.value() == 1 and state == "idle":
        state = "counting"
        utime.sleep(0.3)

✅ Start Button Logic

• When pressed, changes state to "counting" to begin counting.
• Debounce delay avoids double-press detection.

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if state == "counting":
        display_number(count)
        green_led.toggle()
        beep_short()
        utime.sleep(1)
        count += 1
        if count > 9:
            count = 9
            state = "done"
            green_led.value(0)

✅ Counting Logic

• Displays current number.
• Blinks green LED and beeps during counting.
• After each second, increases count.
• If count exceeds 9, stop counting and switch to "done" state.

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 if state == "done":
        red_led.value(1)
        beep_long()
        red_led.value(0)
        count = 0
        display_number(count)
        state = "idle"

✅ When Count Reaches 9

• Red LED turns ON.
• Long 3-second beep is played.
• System auto-resets to 0 and returns to idle state.

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🎓 Wrap-Up

With this explanation, even first-time coders or school students can:

✅ Understand how microcontrollers interact with displays, buttons, and sensors
✅ Build structured logic using states (idle, counting, done)
✅ Use sound and light feedback in real projects

🧪 Try This!

• Change the delay to 0.5s for faster counting.
• Add a second 7-segment display to show 2 digits.
• Try displaying countdown (from 9 to 0).
• Replace buzzer with speaker for different tones.

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📷 Project Snapshot

(You can add a labeled breadboard image here showing connections.)

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📘 Summary

You just built a smart digital counter with:
✅ Visual Display
✅ Audio Feedback
✅ State-based logic (Start, Stop, Auto-reset)
✅ Button interaction
✅ Beginner-friendly MicroPython logic

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🔚 What’s Next?

• Use a Pico W to control it from your phone
• Display the count on an OLED screen
• Use this system as a timer, voting machine, or event counter