Python
#!/usr/bin/env python3
import time
import argparse

def main():
    parser = argparse.ArgumentParser(description="Emulate a 555 LED blinker by printing LED ON/OFF.")
    parser.add_argument("--r1", type=float, default=33000.0, help="R1 in ohms (default: 33000)")
    parser.add_argument("--r2", type=float, default=33000.0, help="R2 in ohms (default: 33000)")
    parser.add_argument("--c",  type=float, default=10e-6,    help="C in farads (default: 10e-6)")
    parser.add_argument("--on-label",  default="LED ON",  help="Text to print when LED is on")
    parser.add_argument("--off-label", default="LED OFF", help="Text to print when LED is off")
    args = parser.parse_args()

    # 555 astable equations:
    # t_high = 0.693 * (R1 + R2) * C
    # t_low  = 0.693 * R2 * C
    # f ≈ 1 / (t_high + t_low) = 1.44 / ((R1 + 2*R2) * C)
    t_high = 0.693 * (args.r1 + args.r2) * args.c
    t_low  = 0.693 * args.r2 * args.c
    period = t_high + t_low
    freq   = 1.0 / period if period > 0 else 0.0
    duty   = t_high / period if period > 0 else 0.0

    print("555 LED blink emulator")
    print(f"R1 = {args.r1:.0f} Ω, R2 = {args.r2:.0f} Ω, C = {args.c} F")
    print(f"t_high = {t_high:.3f} s, t_low = {t_low:.3f} s, period = {period:.3f} s")
    print(f"freq ≈ {freq:.3f} Hz, duty ≈ {duty*100:.1f}%")
    print("Press Ctrl+C to stop.\n")

    try:
        while True:
            print(args.on_label, flush=True)
            time.sleep(max(t_high, 0.0))
            print(args.off_label, flush=True)
            time.sleep(max(t_low, 0.0))
    except KeyboardInterrupt:
        print("\nStopped.")

if __name__ == "__main__":
    main()

• Save as blink.py and run: python blink.py
• Optional: python blink.py --r1 33000 --r2 33000 --c 10e-6
• Stop with Ctrl+C.