Beginner · MicroPython · Wokwi
7-Segment Display Counter with Raspberry Pi Pico
Wire a 7-segment display and build a bidirectional counter (0–F) controlled by a slide switch — simulated in Wokwi, no hardware required.
Open Free SimulationWhat is a 7-Segment Display?
A 7-segment display is an LED arrangement that can show digits 0–9 and hex letters A–F. It has 7 individual LED segments (labelled A–G) plus a decimal point (DP), arranged in a figure-8 pattern to form numbers and characters.
This project uses a common anode type — the common pin is connected to 3.3 V, and each segment is switched on by pulling its GPIO pin LOW.
⬆️ Switch UP — Ascending Mode
- Counter counts 0 → 1 → 2 → … → F
- Each digit displays for 0.5 seconds
- Loops back to 0 automatically
⬇️ Switch DOWN — Descending Mode
- Counter counts F → E → D → … → 0
- Direction switches mid-sequence
- Great for countdown timers
Segment Layout & Pin Guide
Common Anode Type
| Seg | Position | GPIO |
|---|---|---|
| A | Top horizontal | GP2 |
| B | Top right vertical | GP3 |
| C | Bottom right vertical | GP4 |
| D | Bottom horizontal | GP5 |
| E | Bottom left vertical | GP6 |
| F | Top left vertical | GP8 |
| G | Middle horizontal | GP7 |
| • | Decimal point (DP) | GP0 |
| Common (COM) — Anode to 3V3 | 3V3 | |
⚠️ Common Anode vs Common Cathode
This project uses common anode. The shared pin goes to 3.3 V, and segments turn ON when their GPIO is pulled LOW (0). If you use a common cathode display, invert the 0/1 values in the digit patterns array.
Components Used
| # | Component | Role | Note |
|---|---|---|---|
| 1 | Raspberry Pi Pico | Main microcontroller | MicroPython v1.19+ |
| 2 | 7-Segment Display | Visual digit output | Common anode type |
| 3 | Slide Switch | Count direction selector | UP = ascend, DOWN = descend |
| 4 | Mini Breadboard | Circuit connections | wokwi-breadboard-mini |
| 5 | 220Ω Resistors | Segment current limiting | Optional in simulation |
| 6 | Jumper Wires | Wiring | Multiple colors |
Wiring & Pin Map
Full segment-to-GPIO mapping and power connections for this project:
| Segment / Pin | GPIO | Wire Color | Notes |
|---|---|---|---|
| A Top horizontal | GP2 | Green | — |
| B Top-right vertical | GP3 | Green | — |
| C Bottom-right vertical | GP4 | Green | — |
| D Bottom horizontal | GP5 | Green | — |
| E Bottom-left vertical | GP6 | Green | — |
| F Top-left vertical | GP8 | Green | — |
| G Middle horizontal | GP7 | Green | — |
| DP Decimal point | GP0 | Grey | Not connected (optional) |
| COM.1 / COM.2 — Common anode | 3V3 | Red | Via breadboard rail |
| Slide switch centre pin | GP13 | Orange | Input, reads direction |
| Slide switch GND side | GND.3 | Black | — |
| Slide switch 3V3 side | 3V3 | Red | — |
💡 How the Slide Switch Works
When the switch is in position UP, GP13 reads
1 (HIGH) → counter ascends. When flipped DOWN, GP13 reads 0 (LOW) → counter descends. The code checks the switch value at each digit display cycle and can break mid-sequence to respond immediately.
Circuit Diagram (diagram.json)
Paste this into the diagram.json tab in your Wokwi project. It will automatically place all components and create all wired connections.
{
"version": 1,
"author": "Uri Shaked, Anderson Costa",
"editor": "wokwi",
"parts": [
{ "type": "wokwi-breadboard-mini", "id": "bb1", "top": -11, "left": 7.2, "attrs": {} },
{
"type": "wokwi-pi-pico",
"id": "pico",
"top": 125,
"left": 65.25,
"rotate": 90,
"attrs": { "env": "micropython-20220618-v1.19.1" }
},
{
"type": "wokwi-7segment",
"id": "sevseg1",
"top": 14.58,
"left": 72.28,
"attrs": { "common": "anode" }
},
{
"type": "wokwi-slide-switch",
"id": "sw1",
"top": -34,
"left": 22.3,
"attrs": { "bounce": "0" }
}
],
"connections": [
[ "pico:GP0", "$serialMonitor:RX", "", [] ],
[ "pico:GP1", "$serialMonitor:TX", "", [] ],
[ "pico:GP2", "bb1:16b.j", "green", [ "v0" ] ],
[ "bb1:10t.a", "bb1:16t.a", "green", [ "v0" ] ],
[ "bb1:11t.b", "bb1:15t.b", "green", [ "v0" ] ],
[ "pico:GP3", "bb1:15b.j", "green", [ "v0" ] ],
[ "bb1:15b.f", "bb1:15t.e", "green", [ "v0" ] ],
[ "bb1:16b.f", "bb1:16t.e", "green", [ "v0" ] ],
[ "pico:3V3", "bb1:17b.j", "red", [ "v18", "h61.45", "v-100.71", "h-42.25" ] ],
[ "bb1:17t.a", "bb1:9t.a", "red", [ "v-9.56", "h-76.8" ] ],
[ "pico:GP4", "bb1:10b.j", "green", [ "v-58", "h-38.4" ] ],
[ "pico:GP5", "bb1:8b.j", "green", [ "v-48", "h-48" ] ],
[ "pico:GP6", "bb1:7b.j", "green", [ "v-38", "h-38.4" ] ],
[ "pico:GP7", "bb1:6b.j", "green", [ "v-28", "h-38.4" ] ],
[ "pico:GP8", "bb1:5b.j", "green", [ "v-18", "h-38.4" ] ],
[ "pico:GP13", "bb1:3b.j", "orange",[ "v0" ] ],
[ "bb1:3b.f", "bb1:3t.e", "orange",[ "v0" ] ],
[ "bb1:4b.f", "bb1:4t.e", "black", [ "v0" ] ],
[ "pico:3V3", "bb1:2b.j", "red", [ "v18", "h-158.39", "v-99.76", "h241.39" ] ],
[ "bb1:5t.a", "bb1:8t.a", "green", [ "v0" ] ],
[ "bb1:6t.b", "bb1:7t.b", "green", [ "v0" ] ],
[ "bb1:17t.e", "bb1:17b.f", "red", [ "v0" ] ],
[ "bb1:2t.e", "bb1:2b.f", "red", [ "v0" ] ],
[ "bb1:5b.f", "bb1:5t.e", "green", [ "v0" ] ],
[ "bb1:6b.f", "bb1:6t.e", "green", [ "v0" ] ],
[ "sevseg1:COM.1", "bb1:9b.h", "", [ "$bb" ] ],
[ "sevseg1:COM.2", "bb1:9t.c", "", [ "$bb" ] ],
[ "sevseg1:A", "bb1:10t.c", "", [ "$bb" ] ],
[ "sevseg1:B", "bb1:11t.c", "", [ "$bb" ] ],
[ "sevseg1:C", "bb1:10b.h", "", [ "$bb" ] ],
[ "sevseg1:D", "bb1:8b.h", "", [ "$bb" ] ],
[ "sevseg1:E", "bb1:7b.h", "", [ "$bb" ] ],
[ "sevseg1:F", "bb1:8t.c", "", [ "$bb" ] ],
[ "sevseg1:G", "bb1:7t.c", "", [ "$bb" ] ],
[ "sevseg1:DP", "bb1:11b.h", "", [ "$bb" ] ],
[ "sw1:1", "bb1:2t.a", "", [ "$bb" ] ],
[ "sw1:2", "bb1:3t.a", "", [ "$bb" ] ],
[ "sw1:3", "bb1:4t.a", "", [ "$bb" ] ],
[ "bb1:4b.j", "pico:GND.3", "black", [ "v76.8", "h38.4" ] ]
],
"serialMonitor": { "display": "terminal" },
"dependencies": {}
}
Digit Bit Patterns (A–F hex)
Each digit is represented as an 8-bit array — one value per segment [A, B, C, D, E, F, G, DP]. For common anode: 0 = segment ON, 1 = segment OFF.
0
0,0,0,0,0,0,1,1
1
1,0,0,1,1,1,1,1
2
0,0,1,0,0,1,0,1
3
0,0,0,0,1,1,0,1
4
1,0,0,1,1,0,0,1
5
0,1,0,0,1,0,0,1
6
0,1,0,0,0,0,0,1
7
0,0,0,1,1,1,1,1
8
0,0,0,0,0,0,0,1
9
0,0,0,1,1,0,0,1
A
0,0,0,1,0,0,0,1
b
1,1,0,0,0,0,0,1
C
0,1,1,0,0,0,1,1
d
1,0,0,0,0,1,0,1
E
0,1,1,0,0,0,0,1
F
0,1,1,1,0,0,0,1
Complete MicroPython Code
Paste this into main.py in your Wokwi project or on your physical Pico.
from machine import Pin from utime import sleep # ────────────────────────────────────────────────── # 7-segment display layout (common anode) # # A # --- # F | G | B # --- # E | | C # --- # D # ────────────────────────────────────────────────── # GPIO pin assignment: [A, B, C, D, E, F, G, DP] pins = [ Pin(2, Pin.OUT), # A — top horizontal Pin(3, Pin.OUT), # B — top-right vertical Pin(4, Pin.OUT), # C — bottom-right vertical Pin(5, Pin.OUT), # D — bottom horizontal Pin(6, Pin.OUT), # E — bottom-left vertical Pin(8, Pin.OUT), # F — top-left vertical Pin(7, Pin.OUT), # G — middle horizontal Pin(0, Pin.OUT), # DP — decimal point (not used) ] # ────────────────────────────────────────────────── # Common anode: 0 = segment ON, 1 = segment OFF # Pattern order: [A, B, C, D, E, F, G, DP] # ────────────────────────────────────────────────── digits = [ [0, 0, 0, 0, 0, 0, 1, 1], # 0 [1, 0, 0, 1, 1, 1, 1, 1], # 1 [0, 0, 1, 0, 0, 1, 0, 1], # 2 [0, 0, 0, 0, 1, 1, 0, 1], # 3 [1, 0, 0, 1, 1, 0, 0, 1], # 4 [0, 1, 0, 0, 1, 0, 0, 1], # 5 [0, 1, 0, 0, 0, 0, 0, 1], # 6 [0, 0, 0, 1, 1, 1, 1, 1], # 7 [0, 0, 0, 0, 0, 0, 0, 1], # 8 [0, 0, 0, 1, 1, 0, 0, 1], # 9 [0, 0, 0, 1, 0, 0, 0, 1], # A [1, 1, 0, 0, 0, 0, 0, 1], # b [0, 1, 1, 0, 0, 0, 1, 1], # C [1, 0, 0, 0, 0, 1, 0, 1], # d [0, 1, 1, 0, 0, 0, 0, 1], # E [0, 1, 1, 1, 0, 0, 0, 1], # F ] # ────────────────────────────────────────────────── # Helper: turn all segments OFF # ────────────────────────────────────────────────── def reset(): """Turns off all segments (common anode = set HIGH).""" for pin in pins: pin.value(1) reset() # Slide switch on GP13 switch = Pin(13, Pin.IN) # ────────────────────────────────────────────────── # Main loop # ────────────────────────────────────────────────── while True: if switch.value() == 1: # ⬆️ Ascending counter: 0 → F for i in range(len(digits)): if switch.value() == 0: break for j in range(len(pins) - 1): pins[j].value(digits[i][j]) sleep(0.5) else: # ⬇️ Descending counter: F → 0 for i in range(len(digits) - 1, -1, -1): if switch.value() == 1: break for j in range(len(pins)): pins[j].value(digits[i][j]) sleep(0.5)
Step-by-Step Build Guide
1
Open Wokwi and Start a New Project
Go to wokwi.com and click New Project. Select Raspberry Pi Pico as your board and choose MicroPython. A default
main.py and diagram.json file will be created.2
Paste diagram.json
Click the diagram.json tab in the Wokwi editor. Select all existing content and replace it with the full JSON above. When you save, the simulator will automatically place the Pico, 7-segment display, breadboard, and slide switch — and wire them all up.
3
Understand the 7-Segment Display Type
This project uses a common anode display. The
"common": "anode" attribute in the diagram sets this. In common anode mode, writing 0 to a GPIO turns the segment ON; writing 1 turns it OFF. The reset() function sets all pins HIGH (all segments off) on startup.4
Paste the MicroPython Code
Click the main.py tab and replace everything with the full code above. The code defines the
pins list (8 GPIOs), a 2D digits array with all 16 hex patterns, and a main loop that reads the slide switch to choose direction.5
Run the Simulation
Click the green ▶ Play button. The 7-segment display should start counting upward: 0 → 1 → 2 → … → F, changing every 0.5 seconds. If nothing shows, verify the
diagram.json was pasted correctly and the display type is set to anode.6
Test the Slide Switch
Click on the slide switch in the Wokwi canvas to toggle it. The counter should immediately switch to descending order: F → E → D → … → 0. The code checks the switch state at each digit, so direction changes take effect at the next step — within 0.5 seconds.
7
Add Resistors for Real Hardware
In Wokwi the simulation works without resistors. But if you build this on a physical Pico, add a 220Ω resistor in series with each segment pin (A–G, DP) to limit current and protect both the Pico's GPIO and the display LEDs. Without resistors, each segment can draw up to 20 mA — well over the Pico's 16 mA per GPIO limit.
8
Try on Physical Hardware (Optional)
Flash MicroPython to your Pico using Thonny IDE. Wire each segment through a 220Ω resistor to the corresponding GPIO, connect COM to 3.3 V, and wire the slide switch to GP13, GND, and 3.3 V. Copy
main.py to the board and run.
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