pymcu-sevenseg

A PyMCU library for controlling a single-digit 7-segment display on bare-metal AVR (Arduino Uno / ATmega328P) firmware no interpreter, no runtime, compiled straight to machine code.

Supports Common Anode and Common Cathode displays, digits 0–9, most A–Z / a–z letters that are renderable on a 7-segment display, common symbols, and an optional decimal point (DP).

• Author: Kritish Mohapatra
• License: MIT
• Year: 2026

Ported from the original micropython-sevenseg library to PyMCU's statically-typed Python subset. Validated on real Arduino Uno hardware via pymcu build and pymcu flash.

Installation

pip install --pre pymcu-sevenseg

Wiring

Connect each segment pin (a–g) through a current-limiting resistor (220–330Ω) to a digital pin on the Arduino Uno. Connect the display's common pin(s) to GND (common cathode) or 5V (common anode).

Usage

from machine import Pin
from utime import sleep_ms
from sevenseg import SevenSeg

def main():
    # Common Cathode configuration with DP on Pin 9
    display = SevenSeg(2, 3, 4, 5, 6, 7, 8, pin_dp=9, has_dp=True, common_anode=False)

    count: uint8 = 0
    while True:
        display.show(count)
        sleep_ms(1000)
        count = count + 1
        if count > 9:
            count = 0

API Reference

SevenSeg(pin_a, pin_b, pin_c, pin_d, pin_e, pin_f, pin_g, pin_dp=0, has_dp=False, common_anode=False)

Creates a display driver instance. All pin arguments must be compile-time constant integers (const[uint8]).

• pin_a ... pin_g — Segment pin numbers.
• pin_dp — Decimal point pin number. Ignored unless has_dp=True.
• has_dp — Whether a decimal point pin is wired (True / False).
• common_anode — True for Common Anode displays, False (default) for Common Cathode.

show(digit, dp=False)

Displays a character. Accepts either a plain numeric digit (0–9) or an ASCII code (uint8).

• Digits: 0–9 (or ASCII 48–57).
• Letters: Most renderable uppercase and lowercase characters (e.g. ord('A') / 65, ord('b') / 98). Note: characters like K, M, V, W, X cannot be rendered clearly on 7 segments and are skipped.
• Symbols: - _ . ! ? ' " [ ] = + ^ and space.
• dp — Turn the decimal point on for this character (active only when has_dp=True). Note: characters . and ! automatically enable the decimal point.

clear()

Turns off all segments and the decimal point immediately.

Notes & Constraints

• Compile-Time Pin Constants: Pin numbers must be literals known at compile time — this is a PyMCU language constraint (compile-time pin resolution), not a driver limitation.
• Zero-Heap Design: Does not allocate dynamic memory on the heap; compiles directly to efficient static AVR assembly instructions.
• Backend Compatibility: Tested and verified with pymcu-compiler[avr] (beta as of 0.1.0a10).