from machine import Pin
from rp2 import PIO, StateMachine, asm_pio
from time import sleep_ms, sleep_us
from random import randint

LEDS = 3
PIN = Pin(16)

"""
inspired by https://github.com/raspberrypi/pico-micropython-examples/blob/master/pio/pio_ws2812.py
I made this for no other purpose than learning
took me a few hours to understand pio, but if I did it you can too

ws2811 has different timing:
0 - 250ns, then 1000ns
1 - 600ns, then 650ns
rpi cpu cycle = 8ns

to make things easier, we can split timing:
0 -> 250ns high + 350 low  + 650 low
1 -> 250ns high + 350 high + 650 low

p1 -> 250ns = 31.25 cycles
p2 -> 350ns = 43.75 cycles
p3 -> 650ns = 81.25 cycles
decimal, but it's fine if it's off by some, so we can round
"""

@asm_pio(sideset_init=PIO.OUT_LOW,
         out_shiftdir=PIO.SHIFT_LEFT,
         autopull=True, pull_thresh=24)
def prog():
    label("loop")
    
    # 3rd part
    nop().side(0).delay(14) # 15
    nop().side(0).delay(14) # 30
    nop().side(0).delay(14) # 45 
    nop().side(0).delay(14) # 60
    nop().side(0).delay(14) # 75
    out(x, 1).side(0).delay(5) # 81. get one bit of color
    
    # 1st part
    nop().side(1).delay(15) # 16
    jmp(not_x, "zero").side(1).delay(14) # 31. check if zero
    
    # 2nd part for 1 bit
    nop().side(1).delay(14) # 15
    nop().side(1).delay(14) # 30
    jmp("loop").side(1).delay(12) # 43
    
    # 2nd part for 0 bit
    label("zero")
    nop().side(0).delay(14) # 15
    nop().side(0).delay(14) # 30
    nop().side(0).delay(12) # 43

sm = StateMachine(0, prog, sideset_base=PIN)
sm.active(1)

while True:
    for i in range(LEDS):
        sm.put(randint(0, 0xFFFFFF), 8) # I still don't know why 8 not 24
        
    sleep_ms(500)