Initial implementation of I2CDisplay. (Closes #2)

This is based on the work of:
 * @eteq https://github.com/adafruit/Adafruit_Blinka_Displayio/pull/41
 * @wolfmanjm https://github.com/adafruit/Adafruit_Blinka_Displayio/pull/41#issuecomment-804889522

diff --git a/displayio/i2cdisplay.py b/displayio/i2cdisplay.py
index fd498a70124526be0f7d34c4a4629bffd4e24942..238f98dda33f3c64b62e85db3d6ec6c21f450b6c 100644 (file)
--- a/displayio/i2cdisplay.py
+++ b/displayio/i2cdisplay.py
@@ -1,4 +1,7 @@
 # SPDX-FileCopyrightText: 2020 Melissa LeBlanc-Williams for Adafruit Industries
+# SPDX-FileCopyrightText: 2020 Erik Tollerud
+# SPDX-FileCopyrightText: 2021 Jim Morris
+# SPDX-FileCopyrightText: 2021 James Carr
 #
 # SPDX-License-Identifier: MIT
 
@@ -13,7 +16,7 @@ displayio for Blinka
 * Adafruit Blinka:
   https://github.com/adafruit/Adafruit_Blinka/releases
 
-* Author(s): Melissa LeBlanc-Williams
+* Author(s): Melissa LeBlanc-Williams, Erik Tollerud, James Carr
 
 """
 
@@ -21,13 +24,30 @@ __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_Blinka_displayio.git"
 
 
+import time
+import busio
+import digitalio
+import microcontroller
+
+try:
+    from typing import Optional
+    from typing import ReadableBuffer
+except ImportError:
+    pass
+
+
 class I2CDisplay:
     """Manage updating a display over I2C in the background while Python code runs.
     It doesn’t handle display initialization.
     """
 
-    def __init__(self, i2c_bus, *, device_address, reset=None):
-        # pylint: disable=unnecessary-pass
+    def __init__(
+        self,
+        i2c_bus: busio.I2C,
+        *,
+        device_address: int,
+        reset: Optional[microcontroller.Pin] = None
+    ):
         """Create a I2CDisplay object associated with the given I2C bus and reset pin.
 
         The I2C bus and pins are then in use by the display until displayio.release_displays() is
@@ -36,17 +56,65 @@ class I2CDisplay:
         :py:func`displayio.release_displays` first, otherwise it will error after the first
         code.py run.
         """
-        pass
 
-    def reset(self):
-        """Performs a hardware reset via the reset pin. Raises an exception if called
-        when no reset pin is available.
+        if reset is not None:
+            self._reset = digitalio.DigitalInOut(reset)
+            self._reset.switch_to_output(value=True)
+        else:
+            self._reset = None
+        self._i2c = i2c_bus
+        self._dev_addr = device_address
+
+    def _release(self):
+        self.reset()
+        self._i2c.deinit()
+        if self._reset is not None:
+            self._reset.deinit()
+
+    def reset(self) -> None:
+        """
+        Performs a hardware reset via the reset pin if one is present.
+        """
+
+        if self._reset is None:
+            return
+
+        self._reset.value = False
+        time.sleep(0.0001)
+        self._reset.value = True
+
+    def begin_transaction(self) -> None:
+        """
+        Lock the bus before sending data.
         """
-        raise NotImplementedError("I2CDisplay reset has not been implemented yet")
+        while not self._i2c.try_lock():
+            pass
 
-    def send(self, command, data):
-        """Sends the given command value followed by the full set of data. Display state,
-        such as vertical scroll, set via send may or may not be reset once the code is
+    def send(self, command: bool, data: ReadableBuffer) -> None:
+        """
+        Sends the given command value followed by the full set of data. Display state,
+        such as vertical scroll, set via ``send`` may or may not be reset once the code is
         done.
         """
-        raise NotImplementedError("I2CDisplay send has not been implemented yet")
+
+        if command:
+            n = len(data)
+            if n > 0:
+                command_bytes = bytearray(n * 2)
+                for i in range(n):
+                    command_bytes[2 * i] = 0x80
+                    command_bytes[2 * i + 1] = data[i]
+
+                self._i2c.writeto(self._dev_addr, buffer=command_bytes, stop=True)
+
+        else:
+            data_bytes = bytearray(len(data) + 1)
+            data_bytes[0] = 0x40
+            data_bytes[1:] = data
+            self._i2c.writeto(self._dev_addr, buffer=data_bytes, stop=True)
+
+    def end_transaction(self) -> None:
+        """
+        Release the bus after sending data.
+        """
+        self._i2c.unlock()