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#!/usr/bin/env python3
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at https://mozilla.org/MPL/2.0/.
import argparse
import dataclasses
from decimal import getcontext, Decimal
DESCRIPTION = """Help resistor value calculation for hardware version detection"""
# fmt: off
IMPLEMENTED_SERIES = {
24: (1.0, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.7, 3.0, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2, 6.8, 7.5, 8.2, 9.1),
}
"""Series are hardcoded from Wikipedia since they do not follow the formula"""
# fmt: on
MULTIPLIERS = (
100.0,
1000.0,
10000.0,
)
TOLERANCE = Decimal(1.0)
def main() -> None:
getcontext().prec = 3
args = Arguments.from_cli()
resistors: list[Resistor] = []
for multiplier in MULTIPLIERS:
for value in IMPLEMENTED_SERIES[args.series]:
resistors.append(
Resistor(
resistance=Decimal(multiplier) * Decimal(value),
tolerance=TOLERANCE,
)
)
voltage_dividers = []
for r1 in resistors:
for r2 in resistors:
combination = VoltageDivider(voltage=args.voltage, r1=r1, r2=r2)
voltage_dividers.append(combination)
sorted_voltage_dividers = sorted(voltage_dividers, key=lambda c: c.v_adc)
filtered_voltage_dividers = filter(sorted_voltage_dividers)
results = VoltageDividers(
combinations=tuple[VoltageDivider, ...](filtered_voltage_dividers)
)
print(
results.to_tsv(
voltage=args.voltage,
n_bits_adc=args.n_bits_adc,
)
)
@dataclasses.dataclass(frozen=True, kw_only=True)
class Arguments:
series: int
voltage: Decimal # volts
n_bits_adc: int # number of bits
def __post_init__(self) -> None:
assert isinstance(self.series, int)
assert self.series in IMPLEMENTED_SERIES
assert isinstance(self.voltage, Decimal)
assert 0.0 < self.voltage
assert isinstance(self.n_bits_adc, int)
assert self.n_bits_adc > 0
@staticmethod
def from_cli() -> "Arguments":
parser = argparse.ArgumentParser(
description=DESCRIPTION,
)
parser.add_argument(
"-s",
"--series",
default=24,
help=f"resistor E series (supported: {[k for k in IMPLEMENTED_SERIES]})",
)
parser.add_argument("-v", "--voltage", default=3.3, help="in volts")
parser.add_argument("-b", "--bits", default=12, help="number of ADC bits")
args = parser.parse_args()
return Arguments(
series=int(args.series),
voltage=Decimal(args.voltage),
n_bits_adc=int(args.bits),
)
@dataclasses.dataclass(frozen=True, kw_only=True)
class Resistor:
resistance: Decimal # ohm
tolerance: Decimal # percent
def __post_init__(self) -> None:
assert isinstance(self.resistance, Decimal)
assert self.resistance >= Decimal(0.0)
assert isinstance(self.tolerance, Decimal)
assert self.tolerance >= Decimal(0.0)
def __str__(self) -> str:
return f"{float(self.resistance)} Ohm ({float(self.tolerance)} %)"
@property
def resistance_min(self) -> Decimal:
return self.resistance * (Decimal(1.0) - (self.tolerance / Decimal(100.0)))
@property
def resistance_max(self) -> Decimal:
return self.resistance * (Decimal(1.0) + (self.tolerance / Decimal(100.0)))
@dataclasses.dataclass(frozen=True, kw_only=True)
class VoltageDivider:
voltage: Decimal # voltage over both resistors in volts
r1: Resistor # resistor closer to +
r2: Resistor # resistor closer to -
@property
def power(self) -> Decimal:
return self.voltage**2 / (self.r1.resistance + self.r2.resistance)
@property
def v_adc_min(self) -> Decimal:
return self.voltage / (
Decimal(1.0) + self.r1.resistance_max / self.r2.resistance_min
)
@property
def v_adc(self) -> Decimal:
return self.voltage / (Decimal(1.0) + self.r1.resistance / self.r2.resistance)
@property
def v_adc_max(self) -> Decimal:
return self.voltage / (
Decimal(1.0) + self.r1.resistance_min / self.r2.resistance_max
)
@staticmethod
def volts_to_n_adc(
max_voltage: Decimal, voltage_adc: Decimal, n_bits_adc: int
) -> int:
n_max = 2**n_bits_adc - 1
continuous = voltage_adc / max_voltage * Decimal(n_max)
discrete = int(continuous + Decimal(0.5))
return discrete
def n_adc_min(self, n_bits_adc: int) -> int:
return self.volts_to_n_adc(
max_voltage=self.voltage,
voltage_adc=self.v_adc_min,
n_bits_adc=n_bits_adc,
)
def n_adc(self, n_bits_adc: int) -> int:
return self.volts_to_n_adc(
max_voltage=self.voltage,
voltage_adc=self.v_adc,
n_bits_adc=n_bits_adc,
)
def n_adc_max(self, n_bits_adc: int) -> int:
return self.volts_to_n_adc(
max_voltage=self.voltage,
voltage_adc=self.v_adc_max,
n_bits_adc=n_bits_adc,
)
def to_tsv(self, voltage: Decimal, n_bits_adc: int) -> str:
return (
f"{self.r1}"
f"\t{self.r2}"
f"\t{self.v_adc_min}"
f"\t{self.v_adc}"
f"\t{self.v_adc_max}"
f"\t0x{self.n_adc_min(n_bits_adc=n_bits_adc):03X}"
f"\t0x{self.n_adc(n_bits_adc=n_bits_adc):03X}"
f"\t0x{self.n_adc_max(n_bits_adc=n_bits_adc):03X}"
f"\t{self.power}"
)
@dataclasses.dataclass(frozen=True, kw_only=True)
class VoltageDividers:
combinations: tuple[VoltageDivider, ...]
def to_tsv(self, voltage: Decimal, n_bits_adc: int) -> str:
output = (
"R1"
"\tR2"
"\tV_ADC_min"
"\tV_ADC"
"\tV_ADC_max"
"\tn_ADC_min"
"\tn_ADC"
"\tn_ADC_max"
"\tpower"
)
for combination in self.combinations:
output += "\n" + combination.to_tsv(
voltage=voltage,
n_bits_adc=n_bits_adc,
)
return output
def filter(source: list[VoltageDivider]) -> list[VoltageDivider]:
sink: list[VoltageDivider] = [source[0]]
for combination in source:
candidate_min = combination.v_adc_min
current_max = sink[-1].v_adc_max
if candidate_min > current_max:
sink.append(combination)
return sink
if __name__ == "__main__":
main()
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