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lowlevel.py
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lowlevel.py
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#!/usr/bin/env python3
# Example of low-level Python wrapper for rpi_ws281x library.
# Author: Tony DiCola (tony@tonydicola.com), Jeremy Garff (jer@jers.net)
#
# This is an example of how to use the SWIG-generated _rpi_ws281x module.
# You probably don't want to use this unless you are building your own library,
# because the SWIG generated module is clunky and verbose. Instead look at the
# high level Python port of Adafruit's NeoPixel Arduino library in strandtest.py.
#
# This code will animate a number of WS281x LEDs displaying rainbow colors.
import time
import _rpi_ws281x as ws
# LED configuration.
LED_CHANNEL = 0
LED_COUNT = 32 # How many LEDs to light.
LED_FREQ_HZ = 800000 # Frequency of the LED signal. Should be 800khz or 400khz.
LED_DMA_NUM = 10 # DMA channel to use, can be 0-14.
LED_GPIO = 18 # GPIO connected to the LED signal line. Must support PWM!
LED_BRIGHTNESS = 255 # Set to 0 for darkest and 255 for brightest
LED_INVERT = 0 # Set to 1 to invert the LED signal, good if using NPN
# transistor as a 3.3V->5V level converter. Keep at 0
# for a normal/non-inverted signal.
# Define colors which will be used by the example. Each color is an unsigned
# 32-bit value where the lower 24 bits define the red, green, blue data (each
# being 8 bits long).
DOT_COLORS = [ 0x200000, # red
0x201000, # orange
0x202000, # yellow
0x002000, # green
0x002020, # lightblue
0x000020, # blue
0x100010, # purple
0x200010 ] # pink
# Create a ws2811_t structure from the LED configuration.
# Note that this structure will be created on the heap so you need to be careful
# that you delete its memory by calling delete_ws2811_t when it's not needed.
leds = ws.new_ws2811_t()
# Initialize all channels to off
for channum in range(2):
channel = ws.ws2811_channel_get(leds, channum)
ws.ws2811_channel_t_count_set(channel, 0)
ws.ws2811_channel_t_gpionum_set(channel, 0)
ws.ws2811_channel_t_invert_set(channel, 0)
ws.ws2811_channel_t_brightness_set(channel, 0)
channel = ws.ws2811_channel_get(leds, LED_CHANNEL)
ws.ws2811_channel_t_count_set(channel, LED_COUNT)
ws.ws2811_channel_t_gpionum_set(channel, LED_GPIO)
ws.ws2811_channel_t_invert_set(channel, LED_INVERT)
ws.ws2811_channel_t_brightness_set(channel, LED_BRIGHTNESS)
ws.ws2811_t_freq_set(leds, LED_FREQ_HZ)
ws.ws2811_t_dmanum_set(leds, LED_DMA_NUM)
# Initialize library with LED configuration.
resp = ws.ws2811_init(leds)
if resp != ws.WS2811_SUCCESS:
message = ws.ws2811_get_return_t_str(resp)
raise RuntimeError('ws2811_init failed with code {0} ({1})'.format(resp, message))
# Wrap following code in a try/finally to ensure cleanup functions are called
# after library is initialized.
try:
offset = 0
while True:
# Update each LED color in the buffer.
for i in range(LED_COUNT):
# Pick a color based on LED position and an offset for animation.
color = DOT_COLORS[(i + offset) % len(DOT_COLORS)]
# Set the LED color buffer value.
ws.ws2811_led_set(channel, i, color)
# Send the LED color data to the hardware.
resp = ws.ws2811_render(leds)
if resp != ws.WS2811_SUCCESS:
message = ws.ws2811_get_return_t_str(resp)
raise RuntimeError('ws2811_render failed with code {0} ({1})'.format(resp, message))
# Delay for a small period of time.
time.sleep(0.25)
# Increase offset to animate colors moving. Will eventually overflow, which
# is fine.
offset += 1
finally:
# Ensure ws2811_fini is called before the program quits.
ws.ws2811_fini(leds)
# Example of calling delete function to clean up structure memory. Isn't
# strictly necessary at the end of the program execution here, but is good practice.
ws.delete_ws2811_t(leds)