63 lines
2.1 KiB
Python
63 lines
2.1 KiB
Python
from __future__ import annotations
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from dataclasses import dataclass
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@dataclass(frozen=True)
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class UartTiming:
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baud: int = 38_400
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data_bits: int = 8
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parity: str = "N"
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stop_bits: int = 1
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start_bits: int = 1
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def __post_init__(self) -> None:
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parity = self.parity.upper()
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if parity not in {"N", "E", "O"}:
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raise ValueError("parity must be N, E, or O")
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object.__setattr__(self, "parity", parity)
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@property
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def parity_bits(self) -> int:
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return 0 if self.parity == "N" else 1
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@property
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def bits_per_character(self) -> int:
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return self.start_bits + self.data_bits + self.parity_bits + self.stop_bits
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def seconds_per_character(self) -> float:
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return self.bits_per_character / max(1, self.baud)
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def micros_per_character(self) -> float:
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return 1_000_000.0 * self.seconds_per_character()
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def cycles_per_character(self, clock_hz: int) -> int:
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return max(1, round(max(1, clock_hz) * self.seconds_per_character()))
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def summary(self, clock_hz: int) -> str:
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return (
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f"uart_{self.data_bits}{self.parity}{self.stop_bits} "
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f"baud={self.baud} byte_us={self.micros_per_character():.3f} "
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f"byte_cycles={self.cycles_per_character(clock_hz)}"
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)
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@classmethod
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def from_format(cls, text: str, *, baud: int = 38_400) -> "UartTiming":
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normalized = text.strip().upper()
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if len(normalized) != 3 or normalized[0] not in "78" or normalized[1] not in "NEO" or normalized[2] not in "12":
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raise ValueError(f"unsupported UART format {text!r}; expected 8E1, 8N1, 8O1, etc.")
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return cls(baud=baud, data_bits=int(normalized[0]), parity=normalized[1], stop_bits=int(normalized[2]))
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@classmethod
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def from_sci_smr(cls, smr: int, *, baud: int = 38_400) -> "UartTiming":
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data_bits = 7 if smr & 0x40 else 8
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if smr & 0x20:
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parity = "O" if smr & 0x10 else "E"
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else:
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parity = "N"
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stop_bits = 2 if smr & 0x08 else 1
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return cls(baud=baud, data_bits=data_bits, parity=parity, stop_bits=stop_bits)
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__all__ = ["UartTiming"]
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