Source code for adafruit_bus_device.spi_device

# SPDX-FileCopyrightText: 2016 Scott Shawcroft for Adafruit Industries
# SPDX-License-Identifier: MIT

# pylint: disable=too-few-public-methods

`adafruit_bus_device.spi_device` - SPI Bus Device

import time

    from typing import Optional, Type
    from types import TracebackType

    # Used only for type annotations.
    from busio import SPI
    from digitalio import DigitalInOut
except ImportError:

__version__ = "0.0.0+auto.0"
__repo__ = ""

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