i2cdisplaybus/__init__.py

   1 # SPDX-FileCopyrightText: 2020 Melissa LeBlanc-Williams for Adafruit Industries
   2 # SPDX-FileCopyrightText: 2020 Erik Tollerud
   3 # SPDX-FileCopyrightText: 2021 Jim Morris
   4 # SPDX-FileCopyrightText: 2021 James Carr
   5 #
   6 # SPDX-License-Identifier: MIT
   7
   8 """
   9 `i2cdisplaybus`
  10 ================================================================================
  11
  12 i2cdisplaybus for Blinka
  13
  14 **Software and Dependencies:**
  15
  16 * Adafruit Blinka:
  17   https://github.com/adafruit/Adafruit_Blinka/releases
  18
  19 * Author(s): Melissa LeBlanc-Williams, Erik Tollerud, James Carr
  20
  21 """
  22
  23 import time
  24 from typing import Optional
  25
  26 import busio
  27 import digitalio
  28 from circuitpython_typing import ReadableBuffer
  29 from displayio._constants import CHIP_SELECT_UNTOUCHED, DISPLAY_COMMAND
  30
  31 __version__ = "0.0.0+auto.0"
  32 __repo__ = "https://github.com/adafruit/Adafruit_Blinka_displayio.git"
  33
  34
  35 class I2CDisplayBus:
  36     """Manage updating a display over I2C in the background while Python code runs.
  37     It doesn’t handle display initialization.
  38     """
  39
  40     def __init__(self, i2c_bus: busio.I2C, *, device_address: int, reset=None):
  41         """Create a I2CDisplayBus object associated with the given I2C bus and reset pin.
  42
  43         The I2C bus and pins are then in use by the display until displayio.release_displays() is
  44         called even after a reload. (It does this so CircuitPython can use the display after your
  45         code is done.) So, the first time you initialize a display bus in code.py you should call
  46         :py:func`displayio.release_displays` first, otherwise it will error after the first
  47         code.py run.
  48         """
  49
  50         if reset is not None:
  51             self._reset = digitalio.DigitalInOut(reset)
  52             self._reset.switch_to_output(value=True)
  53         else:
  54             self._reset = None
  55         self._i2c = i2c_bus
  56         self._dev_addr = device_address
  57
  58     def __new__(cls, *args, **kwargs):
  59         from displayio import (  # pylint: disable=import-outside-toplevel, cyclic-import
  60             allocate_display_bus,
  61         )
  62
  63         display_bus_instance = super().__new__(cls)
  64         allocate_display_bus(display_bus_instance)
  65         return display_bus_instance
  66
  67     def _release(self):
  68         self.reset()
  69         self._i2c.deinit()
  70         if self._reset is not None:
  71             self._reset.deinit()
  72
  73     def reset(self) -> None:
  74         """
  75         Performs a hardware reset via the reset pin if one is present.
  76         """
  77
  78         if self._reset is None:
  79             return
  80
  81         self._reset.value = False
  82         time.sleep(0.0001)
  83         self._reset.value = True
  84
  85     def send(self, command: int, data: ReadableBuffer) -> None:
  86         """
  87         Sends the given command value followed by the full set of data. Display state,
  88         such as vertical scroll, set via ``send`` may or may not be reset once the code is
  89         done.
  90         """
  91         self._begin_transaction()
  92         self._send(DISPLAY_COMMAND, CHIP_SELECT_UNTOUCHED, data, command)
  93         self._end_transaction()
  94
  95     def _send(
  96         self,
  97         data_type: int,
  98         _chip_select: int,  # Chip select behavior
  99         data: ReadableBuffer,
 100         command: Optional[int] = None,
 101     ):
 102         if data_type == DISPLAY_COMMAND:
 103             n = len(data)
 104             if command is not None:
 105                 n += 1
 106             if n > 0:
 107                 command_bytes = bytearray(n * 2)
 108                 for i in range(n):
 109                     command_bytes[2 * i] = 0x80
 110                     if command is not None:
 111                         if i > 0:
 112                             command_bytes[2 * i + 1] = data[i]
 113                         else:
 114                             command_bytes[2 * i + 1] = command
 115                     else:
 116                         command_bytes[2 * i + 1] = data[i]
 117
 118             try:
 119                 self._i2c.writeto(self._dev_addr, buffer=command_bytes)
 120             except OSError as error:
 121                 if error.errno == 121:
 122                     raise RuntimeError(
 123                         f"I2C write error to 0x{self._dev_addr:02x}"
 124                     ) from error
 125                 raise error
 126         else:
 127             size = len(data) + 1
 128             if command is not None:
 129                 size += 1
 130             data_bytes = bytearray(size)
 131             data_bytes[0] = 0x40
 132             if command is not None:
 133                 data_bytes[1] = command
 134                 data_bytes[2:] = data
 135             else:
 136                 data_bytes[1:] = data
 137             try:
 138                 self._i2c.writeto(self._dev_addr, buffer=data_bytes)
 139             except OSError as error:
 140                 if error.errno == 121:
 141                     raise RuntimeError(
 142                         f"I2C write error to 0x{self._dev_addr:02x}"
 143                     ) from error
 144                 raise error
 145
 146     def _free(self) -> bool:
 147         """Attempt to free the bus and return False if busy"""
 148         if not self._i2c.try_lock():
 149             return False
 150         self._i2c.unlock()
 151         return True
 152
 153     def _begin_transaction(self) -> bool:
 154         """Lock the bus before sending data."""
 155         return self._i2c.try_lock()
 156
 157     def _end_transaction(self) -> None:
 158         """Release the bus after sending data."""
 159         self._i2c.unlock()