New adafruit_ws2801.py based on https://github.com/adafruit/Adafruit_CircuitPython_DotStar and protocol dervied from https://github.com/adafruit/Adafruit-WS2801-Library/blob/master/Adafruit_WS2801.cpp and tested on a 50 12mm led string.

WS2801 constructor argument brightness unlikely to work at the momemt due to inherited strangeness/bug.

Author: Kevin J Walters

adafruit_ws2801.py

@@ -0,0 +1,201 @@
+# The MIT License (MIT)
+#
+# Copyright (c) 2016 Damien P. George (original Neopixel object)
+# Copyright (c) 2017 Ladyada
+# Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+# Copyright (c) 2018 Kevin Walters
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+"""
+`adafruit_ws2801` - WS2801 LED pixel string driver
+====================================================
+
+* Author(s): Damien P. George, Limor Fried & Scott Shawcroft, Kevin Walters
+"""
+import math
+
+import busio
+import digitalio
+
+__version__ = "0.0.0-auto.0"
+__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_WS2801.git"
+
+### based on https://github.com/adafruit/Adafruit_CircuitPython_DotStar
+
+class WS2801:
+    """
+    A sequence of WS2801 controlled LEDs.
+
+    :param ~microcontroller.Pin clock: The pin to output dotstar clock on.
+    :param ~microcontroller.Pin data: The pin to output dotstar data on.
+    :param int n: The number of LEDs in the chain.
+    :param float brightness: The brightness between 0.0 and (default) 1.0.
+    :param bool auto_write: True if the dotstars should immediately change when
+        set. If False, `show` must be called explicitly.
+
+
+    Example for Gemma M0:
+
+    .. code-block:: python
+
+        import adafruit_ws2801
+        import time
+        from board import *
+
+        RED = 0x100000
+
+        with adafruit_ws2801.WS2801(board.D2, board.D0, 25, brightness=1.0) as pixels:
+            pixels[0] = RED
+            time.sleep(2)
+    """
+
+    def __init__(self, clock, data, n, *, brightness=1.0, auto_write=True):
+        self._spi = None
+        try:
+            self._spi = busio.SPI(clock, MOSI=data)
+            while not self._spi.try_lock():
+                pass
+            self._spi.configure(baudrate=1000*1000)
+        except ValueError:
+            self.dpin = digitalio.DigitalInOut(data)
+            self.cpin = digitalio.DigitalInOut(clock)
+            self.dpin.direction = digitalio.Direction.OUTPUT
+            self.cpin.direction = digitalio.Direction.OUTPUT
+            self.cpin.value = False
+        self._n = n
+        self._buf = bytearray(n * 3)
+        ### TODO - review brightness oddity inherited from adafruit_dotstar
+        self._brightness = 1.0
+        self.brightness = brightness
+        self.auto_write = auto_write
+        ### TODO - review/consider adding GRB support like that in  c++ version
+
+    def deinit(self):
+        """Blank out the DotStars and release the resources."""
+        self.auto_write = False
+        black=(0,0,0)
+        self.fill(black)
+        self.show()
+        if self._spi:
+            self._spi.deinit()
+        else:
+            self.dpin.deinit()
+            self.cpin.deinit()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exception_type, exception_value, traceback):
+        self.deinit()
+
+    def __repr__(self):
+        return "[" + ", ".join([str(x) for x in self]) + "]"
+
+    def _set_item(self, index, value):
+        offset = index * 3
+        if isinstance(value, int):
+            r = value >> 16
+            g = (value >> 8) & 0xff
+            b = value & 0xff
+        else:
+            r, g, b = value
+        # red/green/blue order for WS2801
+        self._buf[offset]     = r
+        self._buf[offset + 1] = g
+        self._buf[offset + 2] = b
+
+    def __setitem__(self, index, val):
+        if isinstance(index, slice):
+            start, stop, step = index.indices(self._n)
+            length = stop - start
+            if step != 0:
+                length = math.ceil(length / step)
+            if len(val) != length:
+                raise ValueError("Slice and input sequence size do not match.")
+            for val_i, in_i in enumerate(range(start, stop, step)):
+                self._set_item(in_i, val[val_i])
+        else:
+            self._set_item(index, val)
+
+        if self.auto_write:
+            self.show()
+
+    def __getitem__(self, index):
+        if isinstance(index, slice):
+            out = []
+            for in_i in range(*index.indices(self._n)):
+                out.append(
+                    tuple(self._buf[in_i * 3 + (2 - i)] for i in range(3)))
+            return out
+        if index < 0:
+            index += len(self)
+        if index >= self._n or index < 0:
+            raise IndexError
+        offset = index * 3
+        return tuple(self._buf[offset + (2 - i)] for i in range(3))
+
+    def __len__(self):
+        return self._n
+
+    @property
+    def brightness(self):
+        """Overall brightness of the pixel"""
+        return self._brightness
+
+    @brightness.setter
+    def brightness(self, brightness):
+        self._brightness = min(max(brightness, 0.0), 1.0)
+
+    def fill(self, color):
+        """Colors all pixels the given ***color***."""
+        auto_write = self.auto_write
+        self.auto_write = False
+        for i, _ in enumerate(self):
+            self[i] = color
+        if auto_write:
+            self.show()
+        self.auto_write = auto_write
+
+    def _ds_writebytes(self, buf):
+        for b in buf:
+            for _ in range(8):
+                self.cpin.value = True
+                self.dpin.value = (b & 0x80)
+                self.cpin.value = False
+                b = b << 1
+
+    def show(self):
+        """Shows the new colors on the pixels themselves if they haven't already
+        been autowritten.
+
+        The colors may or may not be showing after this function returns because
+        it may be done asynchronously."""
+        # Create a second output buffer if we need to compute brightness
+        buf = self._buf
+        if self.brightness < 1.0:
+            buf = bytearray(len(self._buf))
+            for i in range(self._n):
+                buf[i] = int(self._buf[i] * self._brightness)
+
+        if self._spi:
+            self._spi.write(buf)
+        else:
+            self._ds_writebytes(buf)
+            self.cpin.value = False