WS2812 & pico

Support Raspberry Pi
10

Hi Paul,

Not coming at you with any solutions just yet.
I reviewed the code for someone at Core to do a bit of testing with.

I found this page here from the Raspberry Pi Foundation outlining some similar code in C++.

I’ll add some comments with explanations as to what the code is/might be doing (I have marked them with ’ #L - ')


# Example using PIO to drive a set of WS2812 LEDs.

#L - Importing the libraries commonly used in microcontrollers
import array, time
from machine import Pin
import rp2


# Configure the number of WS2812 LEDs.
NUM_LEDS = 13
PIN_NUM = 22
brightness = 0.2

@rp2.asm_pio(sideset_init=rp2.PIO.OUT_LOW, out_shiftdir=rp2.PIO.SHIFT_LEFT, autopull=True, pull_thresh=24)       #L - Initialising the state machine for output, using the following settings
def ws2812():
    T1 = 2                  #L - Defining the timings for an output of either 1 or 0, not important for our case, though if you were using a different LED controller this would be essential
    T2 = 5
    T3 = 3
    wrap_target()
    label("bitloop")
    out(x, 1)               .side(0)    [T3 - 1]
    jmp(not_x, "do_zero")   .side(1)    [T1 - 1]
    jmp("bitloop")          .side(1)    [T2 - 1]
    label("do_zero")
    nop()                   .side(0)    [T2 - 1]
    wrap()


# Create the StateMachine with the ws2812 program, outputting on pin
sm = rp2.StateMachine(0, ws2812, freq=8_000_000, sideset_base=Pin(PIN_NUM))

# Start the StateMachine, it will wait for data on its FIFO.
sm.active(1)

# Display a pattern on the LEDs via an array of LED RGB values.
ar = array.array("I", [0 for _ in range(NUM_LEDS)])

##########################################################################
def pixels_show():
    dimmer_ar = array.array("I", [0 for _ in range(NUM_LEDS)])        #L - The capital i means that it is an integer array and the underscore is used as a variable basically loops through creating an element for each LED


    for i,c in enumerate(ar):            #L - Create the 'packets' to be sent to the WS2812 strip, the 0xFF in short means 100% on, after multiplying the brightness it changes how dim the colour is
        r = int(((c >> 8) & 0xFF) * brightness)
        g = int(((c >> 16) & 0xFF) * brightness)
        b = int((c & 0xFF) * brightness)
        dimmer_ar[i] = (g<<16) + (r<<8) + b
    sm.put(dimmer_ar, 8)               #L - Couldnt find anything on this line, from the sounds of it it puts the dimmer array into the state machine to send, I definitely could be way off the mark here, I would love to learn what exactly this line does!
    time.sleep_ms(10)


#L - Below are some higher level functions that are run automatically

def pixels_set(i, color):
    ar[i] = (color[1]<<16) + (color[0]<<8) + color[2]

def pixels_fill(color):
    for i in range(len(ar)):
        pixels_set(i, color)

def color_chase(color, wait):
    for i in range(NUM_LEDS):
        pixels_set(i, color)
        time.sleep(wait)
        pixels_show()
    time.sleep(0.2)

def wheel(pos):
    # Input a value 0 to 255 to get a color value.
    # The colours are a transition r - g - b - back to r.
    if pos < 0 or pos > 255:
        return (0, 0, 0)
    if pos < 85:
        return (255 - pos * 3, pos * 3, 0)
    if pos < 170:
        pos -= 85
        return (0, 255 - pos * 3, pos * 3)
    pos -= 170
    return (pos * 3, 0, 255 - pos * 3)


def rainbow_cycle(wait):
    for j in range(255):
        for i in range(NUM_LEDS):
            rc_index = (i * 256 // NUM_LEDS) + j
            pixels_set(i, wheel(rc_index & 255))
        pixels_show()
        time.sleep(wait)

BLACK = (0, 0, 0)
RED = (255, 0, 0)
YELLOW = (255, 150, 0)
GREEN = (0, 255, 0)
CYAN = (0, 255, 255)
BLUE = (0, 0, 255)
PURPLE = (180, 0, 255)
WHITE = (255, 255, 255)
COLORS = (BLACK, RED, YELLOW, GREEN, CYAN, BLUE, PURPLE, WHITE)

print("fills")
for color in COLORS:
    pixels_fill(color)
    pixels_show()
    time.sleep(0.2)

print("chases")
for color in COLORS:
    color_chase(color, 0.01)

print("rainbow")
rainbow_cycle(0)

Regards,
Liam.

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