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# SPDX-FileCopyrightText: 2016 Scott Shawcroft for Adafruit Industries
#
# SPDX-License-Identifier: MIT
"""
`adafruit_bus_device.i2c_device` - I2C Bus Device
====================================================
"""
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"
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()
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)
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
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():
pass
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():
pass
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()
|
