add NeoPixel_SPI class

Author: caternuson

neopixel.py

@@ -30,8 +30,13 @@
 
 import math
 
-import digitalio
-from neopixel_write import neopixel_write
+try:
+    # imports needed for main NeoPixel class
+    import digitalio
+    from neopixel_write import neopixel_write
+except:
+    # silently accept this, can still use NeoPixel SPI class
+    pass
 
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_NeoPixel.git"
@@ -230,3 +235,82 @@ def show(self):
             neopixel_write(self.pin, self.buf)
         else:
             neopixel_write(self.pin, bytearray([int(i * self.brightness) for i in self.buf]))
+
+class NeoPixel_SPI(NeoPixel):
+    """
+    A sequence of neopixels.
+
+    :param ~busio.SPI spi: The SPI bus to output neopixel data on.
+    :param int n: The number of neopixels in the chain
+    :param int bpp: Bytes per pixel. 3 for RGB and 4 for RGBW pixels.
+    :param float brightness: Brightness of the pixels between 0.0 and 1.0 where 1.0 is full
+      brightness
+    :param bool auto_write: True if the neopixels should immediately change when set. If False,
+      `show` must be called explicitly.
+    :param tuple pixel_order: Set the pixel color channel order. GRBW is set by default.
+
+    Example:
+
+    .. code-block:: python
+
+        import board
+        import neopixel
+
+        pixels = neopixel.NeoPixel_SPI(board.SPI(), 10)
+        pixels.fill(0xff0000)
+    """
+    #pylint: disable=invalid-name
+
+    FREQ = 6400000  # 800kHz * 8, actual may be different
+    TRST = 80e-6    # Reset code low level time
+
+    def __init__(self, spi, n, *, bpp=3, brightness=1.0, auto_write=True, pixel_order=None):
+        from adafruit_bus_device.spi_device import SPIDevice
+        self._spi = SPIDevice(spi, baudrate=self.FREQ)
+        with self._spi as spi:
+            try:
+                # get actual SPI frequency
+                freq = spi.frequency
+            except AttributeError:
+                # use nominal
+                freq = self.FREQ
+        self.RESET = bytes([0]*round(freq*self.TRST))
+        self.n = n
+        if pixel_order is None:
+            self.order = GRBW
+            self.bpp = bpp
+        else:
+            self.order = pixel_order
+            self.bpp = len(self.order)
+        self.buf = bytearray(self.n * self.bpp)
+        # Set auto_write to False temporarily so brightness setter does _not_
+        # call show() while in __init__.
+        self.auto_write = False
+        self.brightness = brightness
+        self.auto_write = auto_write
+
+    def deinit(self):
+        """Blank out the NeoPixels."""
+        for i in range(len(self.buf)):
+            self.buf[i] = 0
+        self.show()
+
+    def show(self):
+        """Shows the new colors on the pixels themselves if they haven't already
+        been autowritten."""
+        with self._spi as spi:
+            # write out special byte sequence surrounded by RESET
+            # leading RESET needed for cases where MOSI rests HI
+            spi.write(self.RESET + self._transmogrify(self.buf) + self.RESET)
+
+    def _transmogrify(self, buf):
+        """Turn every BIT of buf into a special BYTE pattern."""
+        out_buf = bytearray()
+        for byte in self.buf:
+            # MSB first
+            for i in range(7, -1, -1):
+                if byte >> i & 0x01:
+                    out_buf.append(0b11110000) # A NeoPixel 1 bit
+                else:
+                    out_buf.append(0b11000000) # A NeoPixel 0 bit
+        return out_buf