Code for lighting up a WS2812 LED Strip

ws2812ledstrip.py

from rpi_ws281x import *

# LED strip configuration:
LED_COUNT      = 300      # Number of LED pixels.
LED_PIN        = 18      # GPIO pin connected to the pixels (18 uses PWM!).
#LED_PIN        = 10      # GPIO pin connected to the pixels (10 uses SPI /dev/spidev0.0).
LED_FREQ_HZ    = 800000  # LED signal frequency in hertz (usually 800khz)
LED_DMA        = 10      # DMA channel to use for generating signal (try 10)
LED_BRIGHTNESS = 255     # Set to 0 for darkest and 255 for brightest
LED_INVERT     = False   # True to invert the signal (when using NPN transistor level shift)
LED_CHANNEL    = 0       # set to '1' for GPIOs 13, 19, 41, 45 or 53

strip = Adafruit_NeoPixel(LED_COUNT, LED_PIN, LED_FREQ_HZ,LED_DMA,LED_INVERT,LED_BRIGHTNESS,LED_CHANNEL)
strip.begin()

for x in range(0,LED_COUNT):
    strip.setPixelColor(x,Color(255,0,0))

strip.show()

Hi,

I am new to raspberry pi and coding with python. I was trying your code on my raspberry pi 4 (model B) but it gives errors like this:
Can’t open /dev/mem: Permission denied
Traceback (most recent call last):
File “/home/pi/Documents/glow.py”, line 12, in
Strip.begin()
File “/usr/local/lib/python3.7/dist-packages/rpi_ws281x/rpi_ws281x.py”, line 130, in begin
raise RuntimeError(‘ws2811_init failed with code {0} ({1})’.format(resp, str_resp))
RuntimeError: ws2811_init failed with code -5 (mmap() failed)

The assistant in python also says that 'Adafruit_NeoPixel' and 'Color' are not defined.

Is there something I am doing wrong?

Thanks in advance :)

@daggiemaggie I would suggest signing into your root account, or using sudo before running any commands. For example, sudo python glow.py.

Hi,

I am new to raspberry pi and coding with python. I was trying your code on my raspberry pi 4 (model B) but it gives errors like this:
Can’t open /dev/mem: Permission denied
Traceback (most recent call last):
File “/home/pi/Documents/glow.py”, line 12, in
Strip.begin()
File “/usr/local/lib/python3.7/dist-packages/rpi_ws281x/rpi_ws281x.py”, line 130, in begin
raise RuntimeError(‘ws2811_init failed with code {0} ({1})’.format(resp, str_resp))
RuntimeError: ws2811_init failed with code -5 (mmap() failed)

The assistant in python also says that 'Adafruit_NeoPixel' and 'Color' are not defined.

Is there something I am doing wrong?

Thanks in advance :)

use LED_PIN = 10 instead of LED_PIN = 18
and go to interfaces under raspberry pi configuration and enable all the GPIO related interfaces (eg: SPI)
then without root also your program will work