48 lines
1.4 KiB
Python
48 lines
1.4 KiB
Python
try:
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from typing import Any, Optional
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except ImportError:
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pass
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import sys
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import time
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try:
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from pyb import Pin
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except ImportError:
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from machine import Pin
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from . import SPI_DEFAULT_BAUDRATE, SPI_DUMMY_INT, SPI_TRANSFER_LEN, SPI_HOLD_US
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class SPI:
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def __init__(self, cs: int, baudrate: int = SPI_DEFAULT_BAUDRATE) -> None:
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self._SPICS = Pin(cs, Pin.OUT)
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self._SPI = self.init(baudrate=baudrate) # type: Any
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self.end()
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def init(self, baudrate: int) -> Any:
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raise NotImplementedError
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def start(self) -> None:
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self._SPICS.value(0)
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time.sleep_us(SPI_HOLD_US) # type: ignore
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def end(self) -> None:
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self._SPICS.value(1)
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time.sleep_us(SPI_HOLD_US) # type: ignore
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def transfer(self, value: int = SPI_DUMMY_INT, read: bool = False) -> Optional[int]:
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"""Write int value to SPI and read SPI as int value simultaneously.
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This method supports transfer single byte only,
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and the system byte order doesn't matter because of that. The input and
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output int value are unsigned.
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"""
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value_as_byte = value.to_bytes(SPI_TRANSFER_LEN, sys.byteorder)
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if read:
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output = bytearray(SPI_TRANSFER_LEN)
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self._SPI.write_readinto(value_as_byte, output)
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return int.from_bytes(output, sys.byteorder)
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self._SPI.write(value_as_byte)
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return None
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