1  # The MIT License (MIT)
  2  #
  3  # Copyright (c) 2018 Carter Nelson for 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  """
 23  ``Adafruit_TCA9548A``
 24  ====================================================
 25  
 26  CircuitPython driver for the TCA9548A I2C Multiplexer.
 27  
 28  * Author(s): Carter Nelson
 29  
 30  Implementation Notes
 31  --------------------
 32  
 33  **Hardware:**
 34  
 35  * TCA9548A I2C Multiplexer: https://www.adafruit.com/product/2717
 36  
 37  **Software and Dependencies:**
 38  
 39  * Adafruit CircuitPython firmware for the supported boards:
 40    https://github.com/adafruit/circuitpython/releases
 41  * Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
 42  """
 43  
 44  # imports
 45  from micropython import const
 46  
 47  _DEFAULT_ADDRESS = const(0x70)
 48  
 49  __version__ = "0.0.0-auto.0"
 50  __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_TCA9548A.git"
 51  
 52  
 53  class TCA9548A_Channel:
 54      """Helper class to represent an output channel on the TCA9548A and take care
 55         of the necessary I2C commands for channel switching. This class needs to
 56         behave like an I2CDevice."""
 57  
 58      def __init__(self, tca, channel):
 59          self.tca = tca
 60          self.channel_switch = bytearray([1 << channel])
 61  
 62      def try_lock(self):
 63          """Pass thru for try_lock."""
 64          while not self.tca.i2c.try_lock():
 65              pass
 66          self.tca.i2c.writeto(self.tca.address, self.channel_switch)
 67          return True
 68  
 69      def unlock(self):
 70          """Pass thru for unlock."""
 71          self.tca.i2c.writeto(self.tca.address, b"\x00")
 72          return self.tca.i2c.unlock()
 73  
 74      def readfrom_into(self, address, buffer, **kwargs):
 75          """Pass thru for readfrom_into."""
 76          if address == self.tca.address:
 77              raise ValueError("Device address must be different than TCA9548A address.")
 78          return self.tca.i2c.readfrom_into(address, buffer, **kwargs)
 79  
 80      def writeto(self, address, buffer, **kwargs):
 81          """Pass thru for writeto."""
 82          if address == self.tca.address:
 83              raise ValueError("Device address must be different than TCA9548A address.")
 84          return self.tca.i2c.writeto(address, buffer, **kwargs)
 85  
 86      def writeto_then_readfrom(self, address, buffer_out, buffer_in, **kwargs):
 87          """Pass thru for writeto_then_readfrom."""
 88          # In linux, at least, this is a special kernel function call
 89          if address == self.tca.address:
 90              raise ValueError("Device address must be different than TCA9548A address.")
 91  
 92          if hasattr(self.tca.i2c, "writeto_then_readfrom"):
 93              self.tca.i2c.writeto_then_readfrom(address, buffer_out, buffer_in, **kwargs)
 94          else:
 95              self.tca.i2c.writeto(
 96                  address,
 97                  buffer_out,
 98                  start=kwargs.get("out_start", 0),
 99                  end=kwargs.get("out_end", None),
100                  stop=False,
101              )
102              self.tca.i2c.readfrom_into(
103                  address,
104                  buffer_in,
105                  start=kwargs.get("in_start", 0),
106                  end=kwargs.get("in_end", None),
107              )
108  
109  
110  class TCA9548A:
111      """Class which provides interface to TCA9548A I2C multiplexer."""
112  
113      def __init__(self, i2c, address=_DEFAULT_ADDRESS):
114          self.i2c = i2c
115          self.address = address
116          self.channels = [None] * 8
117  
118      def __len__(self):
119          return 8
120  
121      def __getitem__(self, key):
122          if not 0 <= key <= 7:
123              raise IndexError("Channel must be an integer in the range: 0-7")
124          if self.channels[key] is None:
125              self.channels[key] = TCA9548A_Channel(self, key)
126          return self.channels[key]