65 lines
1.7 KiB
Python
65 lines
1.7 KiB
Python
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from machine import Pin
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from rp2 import PIO, StateMachine, asm_pio
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from time import sleep_ms, sleep_us
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from random import randint
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LEDS = 3
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PIN = Pin(16)
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"""
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inspired by https://github.com/raspberrypi/pico-micropython-examples/blob/master/pio/pio_ws2812.py
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I made this for no other purpose than learning
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took me a few hours to understand pio, but if I did it you can too
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ws2811 has different timing:
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0 - 250ns, then 1000ns
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1 - 600ns, then 650ns
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rpi cpu cycle = 8ns
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to make things easier, we can split timing:
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0 -> 250ns high + 350 low + 650 low
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1 -> 250ns high + 350 high + 650 low
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p1 -> 250ns = 31.25 cycles
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p2 -> 350ns = 43.75 cycles
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p3 -> 650ns = 81.25 cycles
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decimal, but it's fine if it's off by some, so we can round
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"""
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@asm_pio(sideset_init=PIO.OUT_LOW,
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out_shiftdir=PIO.SHIFT_LEFT,
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autopull=True, pull_thresh=24)
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def prog():
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label("loop")
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# 3rd part
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nop().side(0).delay(14) # 15
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nop().side(0).delay(14) # 30
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nop().side(0).delay(14) # 45
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nop().side(0).delay(14) # 60
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nop().side(0).delay(14) # 75
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out(x, 1).side(0).delay(5) # 81. get one bit of color
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# 1st part
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nop().side(1).delay(15) # 16
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jmp(not_x, "zero").side(1).delay(14) # 31. check if zero
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# 2nd part for 1 bit
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nop().side(1).delay(14) # 15
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nop().side(1).delay(14) # 30
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jmp("loop").side(1).delay(12) # 43
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# 2nd part for 0 bit
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label("zero")
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nop().side(0).delay(14) # 15
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nop().side(0).delay(14) # 30
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nop().side(0).delay(12) # 43
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sm = StateMachine(0, prog, sideset_base=PIN)
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sm.active(1)
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while True:
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for i in range(LEDS):
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sm.put(randint(0, 0xFFFFFF), 8) # I still don't know why 8 not 24
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sleep_ms(500)
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