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88 lines
3.6 KiB
88 lines
3.6 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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# pylint: disable=too-few-public-methods
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"""
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`adafruit_register.i2c_bits`
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====================================================
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Multi bit registers
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* Author(s): Scott Shawcroft
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"""
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__version__ = "1.3.1"
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__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_Register.git"
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class RWBits:
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"""
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Multibit register (less than a full byte) that is readable and writeable.
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This must be within a byte register.
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Values are `int` between 0 and 2 ** ``num_bits`` - 1.
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:param int num_bits: The number of bits in the field.
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:param int register_address: The register address to read the bit from
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:param type lowest_bit: The lowest bits index within the byte at ``register_address``
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"""
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def __init__(self, num_bits, register_address, lowest_bit):
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self.bit_mask = 0
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for _ in range(num_bits):
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self.bit_mask = (self.bit_mask << 1) + 1
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self.bit_mask = self.bit_mask << lowest_bit
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if self.bit_mask >= (1 << 8):
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raise ValueError()
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self.buffer = bytearray(2)
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self.buffer[0] = register_address
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self.lowest_bit = lowest_bit
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def __get__(self, obj, objtype=None):
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with obj.i2c_device as i2c:
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i2c.write(self.buffer, end=1, stop=False)
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i2c.readinto(self.buffer, start=1)
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return (self.buffer[1] & self.bit_mask) >> self.lowest_bit
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def __set__(self, obj, value):
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# Shift the value to the appropriate spot and set all bits that aren't
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# ours to 1 (the negation of the bitmask.)
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value = (value << self.lowest_bit) | ~self.bit_mask
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with obj.i2c_device as i2c:
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i2c.write(self.buffer, end=1, stop=False)
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i2c.readinto(self.buffer, start=1)
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# Set all of our bits to 1.
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self.buffer[1] |= self.bit_mask
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# Set all 0 bits to 0 by anding together.
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self.buffer[1] &= value
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i2c.write(self.buffer)
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class ROBits(RWBits):
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"""
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Multibit register (less than a full byte) that is read-only. This must be
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within a byte register.
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Values are `int` between 0 and 2 ** ``num_bits`` - 1.
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:param int num_bits: The number of bits in the field.
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:param int register_address: The register address to read the bit from
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:param type lowest_bit: The lowest bits index within the byte at ``register_address``
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"""
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def __set__(self, obj, value):
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raise AttributeError()
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