PI LED strips

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How to control WS2801 RGB Ledstrip with a Raspberry Pi (model 3)

Following: https://tutorials-raspberrypi.com/how-to-control-a-raspberry-pi-ws2801-rgb-led-strip/


LED strips:WS2801

WS2801B strips have two data lines (data and clock), whereby individual LEDs can be addressed via the integrated SPI bus of the Raspberry Pi.

Connections

Pi GPIOs: SPI

https://www.raspberrypi.org/documentation/hardware/raspberrypi/spi/README.md

The Raspberry Pi is equipped with one Serial Peripheral Interface (SPI) bus that has 2 chip selects.

The SPI master driver is disabled by default on Raspbian.

To enable it, use raspi-config, or ensure the line dtparam=spi=on isn't commented out in /boot/config.txt, and reboot. If the SPI driver was loaded, you should see the device /dev/spidev0.0.


For the this recipe we will use:

  • SPI0_MOSI: Pi PIN 19 (10th pin down left side) - Connected to LED's SI (data)
  • SPI0_CLK: Pi PIN 23 (12th pin down left side) - Connected to LED's CK (clock)
  • Ground: Pi Ground Pin - Connected to LED's GND - Connected to Power supply -
  • 5V: LED's 5V - Connected to Power supply +

PI-GPIO40.png

Power

The LED strip requires 5V and for each around 2A, which is more than the GPIOs of Raspberry Pi can deliver.

Therefore an external current source for the RGB stripe is need.

Wiring of PI + Power to LED should follow the following scheme (Note that Pi's ground is also connected to the LEDs ground pin)

Raspberry-Pi-WS2801B-RGB-LED-Stripe-Schaltplatine-600x296.png


Controlling LEDs

Adafruit created a [ https://github.com/adafruit/Adafruit_Python_WS2801/ python library], design to control the WS2801 LED strips from Python on Pi, which takes care of a lot of the boring work, and let's get right onto controlling the LEDs.

using python 3 (it works):

sudo pip3 install adafruit-ws2801

using python 2:

sudo pip install adafruit-ws2801

installing from source:

git clone https://github.com/adafruit/Adafruit_Python_WS2801.git
cd Adafruit_Python_WS2801
sudo python setup.py install


Examples:

Simple examples can be found in https://github.com/adafruit/Adafruit_Python_WS2801/tree/master/examples



Lifehack agent

  • MOSI: pin (10)19
  • CLK: pin (12) 23
  • Ground

debug

To see if the connections are right, I used the python spidev lib to test the 1st LED

import spidev 
spi = spidev.SpiDev()
spi.open(0,0) # open the device
spi.max_speed_hz = 1000000  

spi.xfer([0b1010100]) # controls the color of first LED
sleep(5)
spi.xfer([0b1010111]) # different color

Other Python libraries for controlling WS2801

https://pypi.org/project/WS2801-RPI/