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111 lines
4.1 KiB
111 lines
4.1 KiB
# The MIT License (MIT)
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#
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# Copyright (c) 2016 Scott Shawcroft for Adafruit Industries
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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# THE SOFTWARE.
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"""
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`adafruit_bus_device.i2c_device` - I2C Bus Device
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====================================================
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"""
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__version__ = "2.2.2"
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__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_BusDevice.git"
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class I2CDevice:
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"""
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Represents a single I2C device and manages locking the bus and the device
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address.
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:param ~busio.I2C i2c: The I2C bus the device is on
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:param int device_address: The 7 bit device address
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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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from board import *
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from adafruit_bus_device.i2c_device import I2CDevice
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with busio.I2C(SCL, SDA) as i2c:
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device = I2CDevice(i2c, 0x70)
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bytes_read = bytearray(4)
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with device:
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device.readinto(bytes_read)
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# A second transaction
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with device:
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device.write(bytes_read)
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"""
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def __init__(self, i2c, device_address):
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# Verify that a deivce with that address exists.
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while not i2c.try_lock():
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pass
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try:
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i2c.writeto(device_address, b'')
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except OSError:
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raise ValueError("No I2C device at address: %x" % device_address)
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finally:
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i2c.unlock()
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self.i2c = i2c
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self.device_address = device_address
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def readinto(self, buf, **kwargs):
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"""
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Read into ``buf`` from the device. The number of bytes read will be the
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length of ``buf``.
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If ``start`` or ``end`` is provided, then the buffer will be sliced
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as if ``buf[start:end]``. This will not cause an allocation like
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``buf[start:end]`` will so it saves memory.
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:param bytearray buffer: buffer to write into
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:param int start: Index to start writing at
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:param int end: Index to write up to but not include
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"""
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self.i2c.readfrom_into(self.device_address, buf, **kwargs)
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def write(self, buf, **kwargs):
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"""
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Write the bytes from ``buffer`` to the device. Transmits a stop bit if
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``stop`` is set.
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If ``start`` or ``end`` is provided, then the buffer will be sliced
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as if ``buffer[start:end]``. This will not cause an allocation like
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``buffer[start:end]`` will so it saves memory.
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:param bytearray buffer: buffer containing the bytes to write
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:param int start: Index to start writing from
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:param int end: Index to read up to but not include
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:param bool stop: If true, output an I2C stop condition after the buffer is written
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"""
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self.i2c.writeto(self.device_address, buf, **kwargs)
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def __enter__(self):
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while not self.i2c.try_lock():
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pass
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return self
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def __exit__(self, *exc):
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self.i2c.unlock()
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return False
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