117 lines
3.8 KiB
Python
117 lines
3.8 KiB
Python
# SPDX-FileCopyrightText: 2016 Scott Shawcroft for Adafruit Industries
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#
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# SPDX-License-Identifier: MIT
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"""
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`adafruit_bus_device.spi_device` - SPI Bus Device
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====================================================
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"""
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import time
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try:
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from types import TracebackType
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from typing import Optional, Type
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# Used only for type annotations.
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from busio import SPI
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from digitalio import DigitalInOut
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except ImportError:
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pass
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__version__ = "5.2.12"
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__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_BusDevice.git"
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class SPIDevice:
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"""
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Represents a single SPI device and manages locking the bus and the device
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address.
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:param ~busio.SPI spi: The SPI bus the device is on
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:param ~digitalio.DigitalInOut chip_select: The chip select pin object that implements the
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DigitalInOut API.
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:param bool cs_active_value: Set to True if your device requires CS to be active high.
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Defaults to False.
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:param int baudrate: The desired SCK clock rate in Hertz. The actual clock rate may be
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higher or lower due to the granularity of available clock settings (MCU dependent).
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:param int polarity: The base state of the SCK clock pin (0 or 1).
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:param int phase: The edge of the clock that data is captured. First (0) or second (1).
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Rising or falling depends on SCK clock polarity.
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:param int extra_clocks: The minimum number of clock cycles to cycle the bus after CS is high.
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(Used for SD cards.)
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.. note:: This class is **NOT** built into CircuitPython. See
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:ref:`here for install instructions <bus_device_installation>`.
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Example:
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.. code-block:: python
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import busio
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import digitalio
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from board import *
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from adafruit_bus_device.spi_device import SPIDevice
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with busio.SPI(SCK, MOSI, MISO) as spi_bus:
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cs = digitalio.DigitalInOut(D10)
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device = SPIDevice(spi_bus, cs)
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bytes_read = bytearray(4)
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# The object assigned to spi in the with statements below
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# is the original spi_bus object. We are using the busio.SPI
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# operations busio.SPI.readinto() and busio.SPI.write().
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with device as spi:
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spi.readinto(bytes_read)
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# A second transaction
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with device as spi:
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spi.write(bytes_read)
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"""
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def __init__(
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self,
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spi: SPI,
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chip_select: Optional[DigitalInOut] = None,
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*,
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cs_active_value: bool = False,
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baudrate: int = 100000,
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polarity: int = 0,
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phase: int = 0,
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extra_clocks: int = 0,
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) -> None:
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self.spi = spi
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self.baudrate = baudrate
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self.polarity = polarity
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self.phase = phase
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self.extra_clocks = extra_clocks
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self.chip_select = chip_select
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self.cs_active_value = cs_active_value
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if self.chip_select:
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self.chip_select.switch_to_output(value=not self.cs_active_value)
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def __enter__(self) -> SPI:
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while not self.spi.try_lock():
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time.sleep(0)
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self.spi.configure(baudrate=self.baudrate, polarity=self.polarity, phase=self.phase)
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if self.chip_select:
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self.chip_select.value = self.cs_active_value
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return self.spi
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def __exit__(
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self,
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exc_type: Optional[Type[type]],
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exc_val: Optional[BaseException],
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exc_tb: Optional[TracebackType],
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) -> bool:
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if self.chip_select:
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self.chip_select.value = not self.cs_active_value
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if self.extra_clocks > 0:
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buf = bytearray(1)
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buf[0] = 0xFF
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clocks = self.extra_clocks // 8
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if self.extra_clocks % 8 != 0:
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clocks += 1
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for _ in range(clocks):
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self.spi.write(buf)
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self.spi.unlock()
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return False
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