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remove math dependency; speedups #24

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merged 1 commit into from
May 24, 2018
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remove math dependency; speedups #24

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16 changes: 9 additions & 7 deletions adafruit_dotstar.py
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,6 @@

* Author(s): Damien P. George, Limor Fried & Scott Shawcroft
"""
import math

import busio
import digitalio

Expand Down Expand Up @@ -160,15 +158,17 @@ def _set_item(self, index, value):
rgb = (value >> 16, (value >> 8) & 0xff, value & 0xff)

if len(value) == 4:
brightness = value[-1]
rgb = value[:3]
brightness = value[3]
# Ignore value[3] below.
else:
brightness = 1

# LED startframe is three "1" bits, followed by 5 brightness bits
# then 8 bits for each of R, G, and B. The order of those 3 are configurable and
# vary based on hardware
brightness_byte = math.ceil(brightness * 31) & 0b00011111
# same as math.ceil(brightness * 31) & 0b00011111
# Idea from https://www.codeproject.com/Tips/700780/Fast-floor-ceiling-functions
brightness_byte = 32 - int(32 - brightness * 31) & 0b00011111
self._buf[offset] = brightness_byte | LED_START
self._buf[offset + 1] = rgb[self.pixel_order[0]]
self._buf[offset + 2] = rgb[self.pixel_order[1]]
Expand All @@ -179,7 +179,9 @@ def __setitem__(self, index, val):
start, stop, step = index.indices(self._n)
length = stop - start
if step != 0:
length = math.ceil(length / step)
# same as math.ceil(length / step)
# Idea from https://fizzbuzzer.com/implement-a-ceil-function/
length = (length + step - 1) // 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)):
Expand Down Expand Up @@ -223,7 +225,7 @@ def fill(self, color):
"""Colors all pixels the given ***color***."""
auto_write = self.auto_write
self.auto_write = False
for i, _ in enumerate(self):
for i in range(self._n):
self[i] = color
if auto_write:
self.show()
Expand Down