Source code for adafruit_bus_device.i2c_device

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

"""
`adafruit_bus_device.i2c_device` - I2C Bus Device
====================================================
"""

import time

try:
    from typing import Optional, Type
    from types import TracebackType
    from circuitpython_typing import ReadableBuffer, WriteableBuffer

    # Used only for type annotations.
    from busio import I2C
except ImportError:
    pass


__version__ = "0.0.0+auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_BusDevice.git"


[docs] class I2CDevice: """ Represents a single I2C device and manages locking the bus and the device address. :param ~busio.I2C i2c: The I2C bus the device is on :param int device_address: The 7 bit device address :param bool probe: Probe for the device upon object creation, default is true .. note:: This class is **NOT** built into CircuitPython. See :ref:`here for install instructions <bus_device_installation>`. Example: .. code-block:: python import busio from board import * from adafruit_bus_device.i2c_device import I2CDevice with busio.I2C(SCL, SDA) as i2c: device = I2CDevice(i2c, 0x70) bytes_read = bytearray(4) with device: device.readinto(bytes_read) # A second transaction with device: device.write(bytes_read) """ def __init__(self, i2c: I2C, device_address: int, probe: bool = True) -> None: self.i2c = i2c self.device_address = device_address if probe: self.__probe_for_device()
[docs] def readinto( self, buf: WriteableBuffer, *, start: int = 0, end: Optional[int] = None ) -> None: """ Read into ``buf`` from the device. The number of bytes read will be the length of ``buf``. If ``start`` or ``end`` is provided, then the buffer will be sliced as if ``buf[start:end]``. This will not cause an allocation like ``buf[start:end]`` will so it saves memory. :param ~WriteableBuffer buffer: buffer to write into :param int start: Index to start writing at :param int end: Index to write up to but not include; if None, use ``len(buf)`` """ if end is None: end = len(buf) self.i2c.readfrom_into(self.device_address, buf, start=start, end=end)
[docs] def write( self, buf: ReadableBuffer, *, start: int = 0, end: Optional[int] = None ) -> None: """ Write the bytes from ``buffer`` to the device, then transmit a stop bit. If ``start`` or ``end`` is provided, then the buffer will be sliced as if ``buffer[start:end]``. This will not cause an allocation like ``buffer[start:end]`` will so it saves memory. :param ~ReadableBuffer buffer: buffer containing the bytes to write :param int start: Index to start writing from :param int end: Index to read up to but not include; if None, use ``len(buf)`` """ if end is None: end = len(buf) self.i2c.writeto(self.device_address, buf, start=start, end=end)
# pylint: disable-msg=too-many-arguments
[docs] def write_then_readinto( self, out_buffer: ReadableBuffer, in_buffer: WriteableBuffer, *, out_start: int = 0, out_end: Optional[int] = None, in_start: int = 0, in_end: Optional[int] = None ) -> None: """ Write the bytes from ``out_buffer`` to the device, then immediately reads into ``in_buffer`` from the device. The number of bytes read will be the length of ``in_buffer``. If ``out_start`` or ``out_end`` is provided, then the output buffer will be sliced as if ``out_buffer[out_start:out_end]``. This will not cause an allocation like ``buffer[out_start:out_end]`` will so it saves memory. If ``in_start`` or ``in_end`` is provided, then the input buffer will be sliced as if ``in_buffer[in_start:in_end]``. This will not cause an allocation like ``in_buffer[in_start:in_end]`` will so it saves memory. :param ~ReadableBuffer out_buffer: buffer containing the bytes to write :param ~WriteableBuffer in_buffer: buffer containing the bytes to read into :param int out_start: Index to start writing from :param int out_end: Index to read up to but not include; if None, use ``len(out_buffer)`` :param int in_start: Index to start writing at :param int in_end: Index to write up to but not include; if None, use ``len(in_buffer)`` """ if out_end is None: out_end = len(out_buffer) if in_end is None: in_end = len(in_buffer) self.i2c.writeto_then_readfrom( self.device_address, out_buffer, in_buffer, out_start=out_start, out_end=out_end, in_start=in_start, in_end=in_end, )
# pylint: enable-msg=too-many-arguments def __enter__(self) -> "I2CDevice": while not self.i2c.try_lock(): time.sleep(0) return self def __exit__( self, exc_type: Optional[Type[type]], exc_val: Optional[BaseException], exc_tb: Optional[TracebackType], ) -> bool: self.i2c.unlock() return False def __probe_for_device(self) -> None: """ Try to read a byte from an address, if you get an OSError it means the device is not there or that the device does not support these means of probing """ while not self.i2c.try_lock(): time.sleep(0) try: self.i2c.writeto(self.device_address, b"") except OSError: # some OS's dont like writing an empty bytesting... # Retry by reading a byte try: result = bytearray(1) self.i2c.readfrom_into(self.device_address, result) except OSError: # pylint: disable=raise-missing-from raise ValueError("No I2C device at address: 0x%x" % self.device_address) # pylint: enable=raise-missing-from finally: self.i2c.unlock()