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from __future__ import annotations

"""

Calculate the frequency and/or duty cycle of an astable 555 timer.

* https://en.wikipedia.org/wiki/555_timer_IC#Astable

These functions take in the value of the external resistances (in ohms)

and capacitance (in Microfarad), and calculates the following:

-------------------------------------

| Freq = 1.44 /[( R1+ 2 x R2) x C1] | ... in Hz

-------------------------------------

where Freq is the frequency,

R1 is the first resistance in ohms,

R2 is the second resistance in ohms,

C1 is the capacitance in Microfarads.

------------------------------------------------

| Duty Cycle = (R1 + R2) / (R1 + 2 x R2) x 100 | ... in %

------------------------------------------------

where R1 is the first resistance in ohms,

R2 is the second resistance in ohms.

"""

def astable_frequency(

resistance_1: float, resistance_2: float, capacitance: float

) -> float:

"""

Usage examples:

>>> astable_frequency(resistance_1=45, resistance_2=45, capacitance=7)

1523.8095238095239

>>> astable_frequency(resistance_1=356, resistance_2=234, capacitance=976)

1.7905459175553078

>>> astable_frequency(resistance_1=2, resistance_2=-1, capacitance=2)

Traceback (most recent call last):

...

ValueError: All values must be positive

>>> astable_frequency(resistance_1=45, resistance_2=45, capacitance=0)

Traceback (most recent call last):

...

ValueError: All values must be positive

"""

if resistance_1 <= 0 or resistance_2 <= 0 or capacitance <= 0:

raise ValueError("All values must be positive")

return (1.44 / ((resistance_1 + 2 * resistance_2) * capacitance)) * 10**6

def astable_duty_cycle(resistance_1: float, resistance_2: float) -> float:

"""

Usage examples:

>>> astable_duty_cycle(resistance_1=45, resistance_2=45)

66.66666666666666

>>> astable_duty_cycle(resistance_1=356, resistance_2=234)

71.60194174757282

>>> astable_duty_cycle(resistance_1=2, resistance_2=-1)

Traceback (most recent call last):

...

ValueError: All values must be positive

>>> astable_duty_cycle(resistance_1=0, resistance_2=0)

Traceback (most recent call last):

...

ValueError: All values must be positive

"""

if resistance_1 <= 0 or resistance_2 <= 0:

raise ValueError("All values must be positive")

return (resistance_1 + resistance_2) / (resistance_1 + 2 * resistance_2) * 100

if __name__ == "__main__":

import doctest

doctest.testmod()

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