✅ Level: Intermediate
🧠 Skills Learned: 7-segment interfacing, button handling, buzzer control, LED blinking, MicroPython logic
🕒 Estimated Time: 2–3 hours

🧰 Components Required

🖼️ Project Overview

This project builds a 2-digit counter (00 to 99) with the following features:

• 🔼 Count up or 🔽 count down using buttons
• ⚙️ Enter Set Mode to manually adjust digits
• 🔁 Reset the counter anytime
• 🔊 Buzzer sounds for feedback and 3-second alert on reaching max/min limit
• 💡 Green LED blinks during counting
• 🚨 Red LED lights up when limit is reached

🧠 Understanding the Logic

✅ Button Functions:

🧠 Special Features:

• Set Mode: Lets you set the tens and ones digits separately
• Limit Alert: On reaching 99 or 00, a 3-second continuous beep and red LED alert are triggered only once

🔌 Circuit Diagram (Wiring)

📺 7-Segment Display:

Connect segment pins a to dp to GPIO 0–7 through 220Ω resistors.

Digit selection pins (common cathode control):

• Digit 1 (Tens): GPIO 16
• Digit 2 (Ones): GPIO 17

🔘 Buttons:

Connect one side of each button to:

• GPIO 10 to 14 as listed above
• Other side to GND
  Add internal pull-down via software (MicroPython handles this)

🔊 Buzzer:

• Connect buzzer +ve to GPIO 15
• GND to negative rail

💡 LEDs:

• Green LED → GPIO 18 (with 220Ω resistor)
• Red LED → GPIO 19 (with 220Ω resistor)

💻 MicroPython Code

👉 Download and install Thonny IDE
👉 Flash MicroPython firmware to your Pico
👉 Create a new file named counter.py, then copy and paste the full code from here:

from machine import Pin, PWM
import utime

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

# Digit control (common cathode control pins)
digit_pins = [Pin(16, Pin.OUT), Pin(17, Pin.OUT)]

# Buzzer setup (PWM on GPIO 15)
buzzer = PWM(Pin(15))

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

# Button setup with pull-down resistors
btn_up = Pin(10, Pin.IN, Pin.PULL_DOWN)
btn_down = Pin(11, Pin.IN, Pin.PULL_DOWN)
btn_confirm = Pin(12, Pin.IN, Pin.PULL_DOWN)
btn_select = Pin(13, Pin.IN, Pin.PULL_DOWN)
btn_setmode = Pin(14, Pin.IN, Pin.PULL_DOWN)

# Digit patterns
digit_patterns = [
    (1,1,1,1,1,1,0,0), (0,1,1,0,0,0,0,0),
    (1,1,0,1,1,0,1,0), (1,1,1,1,0,0,1,0),
    (0,1,1,0,0,1,1,0), (1,0,1,1,0,1,1,0),
    (1,0,1,1,1,1,1,0), (1,1,1,0,0,0,0,0),
    (1,1,1,1,1,1,1,0), (1,1,1,1,0,1,1,0)
]

# Variables
counter = 0
mode = None
set_mode = False
selected_digit = 0
last_tick = utime.ticks_ms()
limit_reached = False

# Beep
def beep(freq=1000, duration=0.05):
    buzzer.freq(freq)
    buzzer.duty_u16(1000)
    utime.sleep(duration)
    buzzer.duty_u16(0)

# Long beep with red LED ON and green LED OFF
def long_beep():
    green_led.value(0)
    red_led.value(1)
    buzzer.freq(1000)
    buzzer.duty_u16(2000)
    utime.sleep(3)
    buzzer.duty_u16(0)
    red_led.value(0)

# Display function with optional blink
def display_digit(pos, digit, blink=False):
    pattern = digit_patterns[digit]
    if blink and utime.ticks_ms() % 400 < 200:
        pattern = (0,0,0,0,0,0,0,0)
    for seg, val in zip(segments, pattern):
        seg.value(val)
    digit_pins[0].value(1)
    digit_pins[1].value(1)
    digit_pins[pos].value(0)
    utime.sleep_ms(5)
    digit_pins[pos].value(1)

# Main loop
while True:
    # Enter Set Mode
    if btn_setmode.value() and not set_mode:
        set_mode = True
        selected_digit = 0
        mode = None
        utime.sleep(0.3)

    if set_mode:
        if btn_up.value():
            if selected_digit == 0 and counter < 90:
                counter += 10
                beep(1000)
            elif selected_digit == 1 and counter % 10 < 9:
                counter += 1
                beep(1000)
            utime.sleep(0.2)

        if btn_down.value():
            if selected_digit == 0 and counter >= 10:
                counter -= 10
                beep(400)
            elif selected_digit == 1 and counter % 10 > 0:
                counter -= 1
                beep(400)
            utime.sleep(0.2)

        if btn_select.value():
            selected_digit = 1 - selected_digit
            beep(600)
            utime.sleep(0.3)

        if btn_confirm.value():
            set_mode = False
            beep(1200)
            utime.sleep(0.3)

        tens = counter // 10
        ones = counter % 10
        for _ in range(10):
            display_digit(0, tens, blink=(selected_digit == 0))
            display_digit(1, ones, blink=(selected_digit == 1))
        continue

    # Button checks
    if btn_up.value():
        mode = 'up'
        utime.sleep(0.3)
    if btn_down.value():
        mode = 'down'
        utime.sleep(0.3)
    if btn_confirm.value():
        counter = 0
        mode = None
        limit_reached = True  # avoid beep at 0
        beep(1500)
        utime.sleep(0.3)
    if btn_select.value():
        mode = None
        utime.sleep(0.3)

    # Counting every 1s
    if mode and utime.ticks_diff(utime.ticks_ms(), last_tick) >= 1000:
        if mode == 'up':
            if counter < 99:
                counter += 1
                beep(1000)
                limit_reached = False
            elif counter == 99 and not limit_reached:
                long_beep()
                limit_reached = True
        elif mode == 'down':
            if counter > 0:
                counter -= 1
                beep(400)
                limit_reached = False
            elif counter == 0 and not limit_reached:
                long_beep()
                limit_reached = True
        last_tick = utime.ticks_ms()

    # Green LED blinking (only if not in long beep mode)
    if not limit_reached:
        green_led.value(utime.ticks_ms() % 500 < 250)  # blink every 250ms

    # Display digits
    tens = counter // 10
    ones = counter % 10
    for _ in range(10):
        display_digit(0, tens)
        display_digit(1, ones)

🚦 How It Works

1. Normal Mode

Press Up or Down to start counting. Green LED blinks.

2. Set Mode

Press Set Mode to enter configuration.
Use Select to switch between digits, and Up/Down to change the value.
Press Confirm to save and exit.

3. Limit Reached

• When counter reaches 99 or 00:
  • A 3-second long beep plays
  • Green LED turns off
  • Red LED glows solid
• Press Reset to start fresh.

🧪 Testing Checklist

✅ Power on your Pico
✅ Confirm all segments light correctly
✅ Test buttons one-by-one
✅ Check beep and LED behavior at limit values
✅ Set mode should allow digit selection and editing

📸 Final Output

• Display: Shows 2-digit counter live
• Buttons: Easily adjust and control
• Buzzer: Click feedback + alert
• LEDs: Visually signal counting and error

💡 Full Code Explanation: 2-Digit Counter with Buzzer & LED Alerts

📦 1. Import Required Modules

pythonCopyEditfrom machine import Pin, PWM
import utime

• Pin: Used to control GPIO pins (input/output).
• PWM: Pulse Width Modulation, used to control buzzer tone.
• utime: Time-related functions like sleep, ticks_ms().

🔌 2. Define 7-Segment Display Pins

pythonCopyEditsegment_pins = [0, 1, 2, 3, 4, 5, 6, 7]
segments = [Pin(pin, Pin.OUT) for pin in segment_pins]

• Segment a to dp are connected to GPIO 0–7.
• Each pin is set as an output to control the LED segments.

🧮 3. Control Common Cathode (Digit Pins)

pythonCopyEditdigit_pins = [Pin(16, Pin.OUT), Pin(17, Pin.OUT)]

• GPIO 16 and 17 control which digit (tens or ones) is active.
• Only one digit is lit at a time using multiplexing.

🔊 4. Buzzer Setup

pythonCopyEditbuzzer = PWM(Pin(15))

• A PWM-controlled buzzer is connected to GPIO 15.
• We use PWM to produce tones and beeps.

🔘 5. Button Setup with Pull-Downs

pythonCopyEditbtn_up = Pin(10, Pin.IN, Pin.PULL_DOWN)
btn_down = Pin(11, Pin.IN, Pin.PULL_DOWN)
btn_confirm = Pin(12, Pin.IN, Pin.PULL_DOWN)
btn_select = Pin(13, Pin.IN, Pin.PULL_DOWN)
btn_setmode = Pin(14, Pin.IN, Pin.PULL_DOWN)

• 5 buttons are connected to GPIO 10–14.
• Each button is configured as input with an internal pull-down resistor (default LOW until pressed).

🧮 6. 7-Segment Digit Patterns

pythonCopyEditdigit_patterns = [
    (1,1,1,1,1,1,0,0),  # 0
    (0,1,1,0,0,0,0,0),  # 1
    ...
    (1,1,1,1,0,1,1,0)   # 9
]

• Each digit is represented by a tuple of 1s and 0s.
• Each position corresponds to a segment (a to g, and dp).
• 1 means ON, 0 means OFF.

📊 7. Initialize Variables

pythonCopyEditcounter = 0
mode = None
set_mode = False
selected_digit = 0
last_tick = utime.ticks_ms()
limit_reached = False

• counter: Holds current number (0–99).
• mode: ‘up’ or ‘down’ for counting.
• set_mode: True when we’re editing digits manually.
• selected_digit: 0 (tens), 1 (ones).
• last_tick: Used to check 1-second intervals.
• limit_reached: Prevents repeated 3s beep at max/min.

🔔 8. Buzzer Functions

pythonCopyEditdef beep(freq=1000, duration=0.05):
    buzzer.freq(freq)
    buzzer.duty_u16(1000)
    utime.sleep(duration)
    buzzer.duty_u16(0)

• Makes a short beep.
• Adjust freq and duration to change tone and length.

pythonCopyEditdef long_beep():
    green_led.value(0)
    red_led.value(1)
    buzzer.freq(1000)
    buzzer.duty_u16(2000)
    utime.sleep(3)
    buzzer.duty_u16(0)
    red_led.value(0)

• Plays a 3-second long alert.
• Turns off green LED and turns on red LED.

🖥️ 9. Display a Digit

pythonCopyEditdef display_digit(pos, digit, blink=False):
    pattern = digit_patterns[digit]
    if blink and utime.ticks_ms() % 400 < 200:
        pattern = (0,0,0,0,0,0,0,0)
    for seg, val in zip(segments, pattern):
        seg.value(val)
    digit_pins[0].value(1)
    digit_pins[1].value(1)
    digit_pins[pos].value(0)
    utime.sleep_ms(5)
    digit_pins[pos].value(1)

• Lights up a digit (tens or ones).
• Uses multiplexing: activates only one digit at a time.
• blink=True makes it flash (used in set mode).

🧠 10. Main Loop Starts

pythonCopyEditwhile True:

Everything inside this loop runs again and again — it’s where logic happens.

⚙️ 11. Enter Set Mode

pythonCopyEditif btn_setmode.value() and not set_mode:
    set_mode = True
    selected_digit = 0
    mode = None
    utime.sleep(0.3)

• If you press the Set button, enter set mode.
• Reset mode so normal counting stops.

🧾 12. Inside Set Mode

pythonCopyEditif set_mode:
    ...
    continue

• Inside this block, user can adjust digits:
  • btn_up/down: change selected digit
  • btn_select: switch between tens and ones
  • btn_confirm: exit set mode
• display_digit(..., blink=True) flashes the active digit

⬆️⬇️ 13. Change Mode with Buttons

pythonCopyEditif btn_up.value():
    mode = 'up'

• Start counting up or down.
• Resets previous mode and sets new one.

🔁 14. Reset Button

pythonCopyEditif btn_confirm.value():
    counter = 0
    mode = None
    limit_reached = True
    beep(1500)

• Resets counter to 0.
• limit_reached = True prevents long beep at 0.

⌛ 15. Counting Every 1 Second

pythonCopyEditif mode and utime.ticks_diff(utime.ticks_ms(), last_tick) >= 1000:

• Checks if 1 second passed since last tick
• If yes, update counter and play a beep

Count Up:

pythonCopyEditif counter < 99:
    counter += 1
    beep(1000)
    limit_reached = False
elif counter == 99 and not limit_reached:
    long_beep()
    limit_reached = True

Count Down:

pythonCopyEditif counter > 0:
    counter -= 1
    beep(400)
    limit_reached = False
elif counter == 0 and not limit_reached:
    long_beep()
    limit_reached = True

• Plays short beep every count
• Plays 3s long beep once on reaching limit
• Prevents repeat with limit_reached flag

💡 16. Green LED Blinking

pythonCopyEditif not limit_reached:
    green_led.value(utime.ticks_ms() % 500 < 250)

• Blinks green LED only if not in limit reached mode
• On for 250ms, off for 250ms → Blinking effect

📺 17. Display Both Digits

pythonCopyEdittens = counter // 10
ones = counter % 10
for _ in range(10):
    display_digit(0, tens)
    display_digit(1, ones)

• Splits the counter into tens and ones
• Displays both by quickly switching digits (multiplexing)

✅ Summary

This project teaches you:

• How to control a 7-segment display
• How to read buttons and use set mode
• How to control a buzzer with PWM
• How to blink LEDs and create alerts
• How to build smart logic using MicroPython

📦 Download

💾 Get the MicroPython .py file + wiring diagram (if needed):
[GitHub Project Link or Google Drive folder] ← Upload your files here and share

🙌 Conclusion

You’ve built a professional-style 2-digit counter system with:

✅ Display
✅ Sound
✅ LED indicators
✅ Smart control

This project teaches how to combine hardware control and MicroPython programming effectively. It’s perfect for electronics students and hobbyists ready to explore deeper into microcontroller logic.