1  # The MIT License (MIT)
  2  #
  3  # Copyright (c) 2016 Adafruit Industries
  4  #
  5  # Permission is hereby granted, free of charge, to any person obtaining a copy
  6  # of this software and associated documentation files (the "Software"), to deal
  7  # in the Software without restriction, including without limitation the rights
  8  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  9  # copies of the Software, and to permit persons to whom the Software is
 10  # furnished to do so, subject to the following conditions:
 11  #
 12  # The above copyright notice and this permission notice shall be included in
 13  # all copies or substantial portions of the Software.
 14  #
 15  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 16  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 17  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 18  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 19  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 20  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 21  # THE SOFTWARE.
 22  # pylint: disable=too-few-public-methods
 23  """
 24  `adafruit_register.i2c_struct`
 25  ====================================================
 26  
 27  Generic structured registers based on `struct`
 28  
 29  * Author(s): Scott Shawcroft
 30  """
 31  
 32  try:
 33      import struct
 34  except ImportError:
 35      import ustruct as struct
 36  
 37  __version__ = "0.0.0-auto.0"
 38  __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_Register.git"
 39  
 40  
 41  class Struct:
 42      """
 43      Arbitrary structure register that is readable and writeable.
 44  
 45      Values are tuples that map to the values in the defined struct.  See struct
 46      module documentation for struct format string and its possible value types.
 47  
 48      :param int register_address: The register address to read the bit from
 49      :param type struct_format: The struct format string for this register.
 50      """
 51  
 52      def __init__(self, register_address, struct_format):
 53          self.format = struct_format
 54          self.buffer = bytearray(1 + struct.calcsize(self.format))
 55          self.buffer[0] = register_address
 56  
 57      def __get__(self, obj, objtype=None):
 58          with obj.i2c_device as i2c:
 59              i2c.write_then_readinto(self.buffer, self.buffer, out_end=1, in_start=1)
 60          return struct.unpack_from(self.format, memoryview(self.buffer)[1:])
 61  
 62      def __set__(self, obj, value):
 63          struct.pack_into(self.format, self.buffer, 1, *value)
 64          with obj.i2c_device as i2c:
 65              i2c.write(self.buffer)
 66  
 67  
 68  class UnaryStruct:
 69      """
 70      Arbitrary single value structure register that is readable and writeable.
 71  
 72      Values map to the first value in the defined struct.  See struct
 73      module documentation for struct format string and its possible value types.
 74  
 75      :param int register_address: The register address to read the bit from
 76      :param type struct_format: The struct format string for this register.
 77      """
 78  
 79      def __init__(self, register_address, struct_format):
 80          self.format = struct_format
 81          self.address = register_address
 82  
 83      def __get__(self, obj, objtype=None):
 84          buf = bytearray(1 + struct.calcsize(self.format))
 85          buf[0] = self.address
 86          with obj.i2c_device as i2c:
 87              i2c.write_then_readinto(buf, buf, out_end=1, in_start=1)
 88          return struct.unpack_from(self.format, buf, 1)[0]
 89  
 90      def __set__(self, obj, value):
 91          buf = bytearray(1 + struct.calcsize(self.format))
 92          buf[0] = self.address
 93          struct.pack_into(self.format, buf, 1, value)
 94          with obj.i2c_device as i2c:
 95              i2c.write(buf)
 96  
 97  
 98  class ROUnaryStruct(UnaryStruct):
 99      """
100      Arbitrary single value structure register that is read-only.
101  
102      Values map to the first value in the defined struct.  See struct
103      module documentation for struct format string and its possible value types.
104  
105      :param int register_address: The register address to read the bit from
106      :param type struct_format: The struct format string for this register.
107      """
108  
109      def __set__(self, obj, value):
110          raise AttributeError()