Simple MicroPython ESP32 RMT NeoPixel / WS2812B driver.

pixels.py

# Copyright public licence and also I don't care.
# 2020 Josh "NeverCast" Lloyd.
from micropython import const 
from esp32 import RMT

# The peripheral clock is 80MHz or 12.5 nanoseconds per clock.
# The smallest precision of timing requried for neopixels is
# 0.35us, but I've decided to go with 0.05 microseconds or
# 50 nanoseconds. 50 nanoseconds = 12.5 * 4 clocks.
# By dividing the 80MHz clock by 4 we get a clock every 50 nanoseconds.

# Neopixel timing in RMT clock counts.
T_0H = const(35 // 5) # 0.35 microseconds / 50 nanoseconds
T_1H = const(70 // 5) # 0.70 microseconds / 50 nanoseconds
T_0L = const(80 // 5) # 0.80 microseconds / 50 nanoseconds
T_1L = const(60 // 5) # 0.60 microseconds / 50 nanoseconds

# Encoded timings for bits 0 and 1.
D_ZERO = (T_0H, T_0L)
D_ONE = (T_1H, T_1L)

# [D_ONE if ((channel >> bit) & 1) else D_ZERO for channel in channels for bit in range(num_bits - 1, -1, -1)]
# Reset signal is low for longer than 50 microseconds.
T_RST = const(510 // 5) # > 50 microseconds / 50 nanoseconds

# Channel width in bits 
CHANNEL_WIDTH = const(8)

class Pixels:
    def __init__(self, pin, pixel_count, rmt_channel=1, pixel_channels=3):
        self.rmt = RMT(rmt_channel, pin=pin, clock_div=4)
        # pixels stores the data sent out via RMT
        self.channels = pixel_channels
        single_pixel = (0,) * pixel_channels
        self.pixels = [D_ZERO * (pixel_channels * CHANNEL_WIDTH)] * pixel_count
        # colors is only used for __getitem__
        self.colors = [single_pixel] * pixel_count

    def write(self):
        # The bus should be idle low ( I think... )
        # So we finish low and start high.
        pulses = tuple()
        for pixel in self.pixels:
            pulses += pixel
        pulses = pulses[:-1] + (T_RST,) # The last low should be long.
        self.rmt.write_pulses(pulses, start=1)

    def __setitem__(self, pixel_index, colors):
        self_colors = self.colors
        self_pixels = self.pixels 
        if isinstance(pixel_index, int):
            # pixels[0] = (r, g, b)
            self_colors[pixel_index] = tuple(colors)
            self_pixels[pixel_index] = tuple(clocks for bit in (D_ONE if ((channel >> bit) & 1) else D_ZERO for channel in colors for bit in range(CHANNEL_WIDTH - 1, -1, -1)) for clocks in bit)
        elif isinstance(pixel_index, slice):
            start = 0 if pixel_index.start is None else pixel_index.start
            stop = len(self.pixels) if pixel_index.stop is None else pixel_index.stop
            step = 1 if pixel_index.step is None else pixel_index.step
            # Assume that if the first colors element is an int, then its not a sequence
            # Otherwise always assume its a sequence of colors
            if isinstance(colors[0], int):
                # pixels[:] = (r,g,b)
                for index in range(start, stop, step):
                    self_colors[index] = tuple(colors)
                    self_pixels[index] = tuple(clocks for bit in (D_ONE if ((channel >> bit) & 1) else D_ZERO for channel in colors for bit in range(CHANNEL_WIDTH - 1, -1, -1)) for clocks in bit)
            else:
                # pixels[:] = [(r,g,b), ...]
                # Assume its a sequence, make it a list so we know the length
                if not isinstance(colors, list):
                    colors = list(colors)
                color_length = len(colors)
                for index in range(start, stop, step):
                    color = colors[(index - start) % color_length]
                    self_colors[index] = tuple(color)
                    self_pixels[index] = tuple(clocks for bit in (D_ONE if ((channel >> bit) & 1) else D_ZERO for channel in color for bit in range(CHANNEL_WIDTH - 1, -1, -1)) for clocks in bit)
        else:
            raise TypeError('Unsupported pixel_index {} ({})'.format(pixel_index, type(pixel_index)))

    def __getitem__(self, pixel_index):
        # slice instances are passed through
        return self.colors[pixel_index]

### All code below this point is test code and can be safely deleted in your own application.

def TEST():
    from machine import Pin
    pin = Pin(18)
    p = Pixels(pin, 5)
    try:
        assert(isinstance(p, Pixels))
        assert(p.channels == 3)
        assert(len(p.colors) == 5)
        assert(len(p.pixels) == 5)
        assert(len(p.colors[0]) == 3)
        assert(sum(p.colors[0]) == 0)
        assert(p[0] == (0, 0, 0))
        old_pixels = p.pixels[0]
        assert(p.pixels[0] == old_pixels)
        p[0] = (1, 2, 3)
        assert(p[0] == (1, 2, 3))
        assert(p.colors[0] == p[0])
        assert(p.pixels[0] != old_pixels)
        assert(p[0:1] == [(1,2,3)])
        assert(p[0:2] == [(1,2,3), (0,0,0)])
        p[0:1] = (1, 3, 5)
        assert(p.colors[0] == (1, 3, 5))
        assert(p.colors[1] == (0, 0, 0))
        assert(p.colors[0:2] == [(1,3,5), (0,0,0)])
        p[0:4] = [(1,1,1), (2,2,2)]
        assert(p.colors[0:4] == [(1,1,1), (2,2,2)]*2)
    finally:
        p.rmt.deinit()
        
    p = Pixels(pin, 5, pixel_channels=4)
    try:
        assert(isinstance(p, Pixels))
        assert(p.channels == 4)
        assert(len(p.colors) == 5)
        assert(len(p.pixels) == 5)
        assert(len(p.colors[0]) == 4)
        assert(sum(p.colors[0]) == 0)
        assert(p[0] == (0, 0, 0, 0))
        old_pixels = p.pixels[0]
        assert(p.pixels[0] == old_pixels)
        p[0] = (1, 2, 3, 4)
        assert(p[0] == (1, 2, 3, 4))
        assert(p.colors[0] == p[0])
        assert(p.pixels[0] != old_pixels)
        assert(p[0:1] == [(1,2,3,4)])
        assert(p[0:2] == [(1,2,3,4), (0,0,0,0)])
        p[0:1] = (1, 3, 5, 7)
        assert(p.colors[0] == (1, 3, 5, 7))
        assert(p.colors[1] == (0, 0, 0, 0))
        assert(p.colors[0:2] == [(1,3,5,7), (0,0,0,0)])
        p[0:4] = [(1,1,1,1), (2,2,2,2)]
        assert(p.colors[0:4] == [(1,1,1,1), (2,2,2,2)]*2)
    finally:
        p.rmt.deinit()

def RAINBOW():
    from machine import Pin
    from time import ticks_ms, ticks_diff
    last = ticks_ms()
    def delta(title=None):
        nonlocal last
        if title is not None:
            print(title,ticks_diff(ticks_ms(), last),'ms')
        last = ticks_ms()
    p = Pin(15)
    pix = Pixels(p, 60)
    rainbow = [[126 , 1 , 0],[114 , 13 , 0],[102 , 25 , 0],[90 , 37 , 0],[78 , 49 , 0],[66 , 61 , 0],[54 , 73 , 0],[42 , 85 , 0],[30 , 97 , 0],[18 , 109 , 0],[6 , 121 , 0],[0 , 122 , 5],[0 , 110 , 17],[0 , 98 , 29],[0 , 86 , 41],[0 , 74 , 53],[0 , 62 , 65],[0 , 50 , 77],[0 , 38 , 89],[0 , 26 , 101],[0 , 14 , 113],[0 , 2 , 125],[9 , 0 , 118],[21 , 0 , 106],[33 , 0 , 94],[45 , 0 , 82],[57 , 0 , 70],[69 , 0 , 58],[81 , 0 , 46],[93 , 0 , 34],[105 , 0 , 22],[117 , 0 , 10]]
    while True:
        rainbow = rainbow[-1:] + rainbow[:-1]
        pix[:] = rainbow
        delta('update')
        pix.write()
        delta('write')

Yep... The interrupt handler could handle multiple strips, it would just need some more work.

Well, I will be waiting for your next update. Kindly do tell me when its done.

Thanks!

@carstenblt

Does your micropython Firmware: https://github.com/carstenblt/micropython
Supports esp32 + psRam, I mean to ask either we have to change some settings or does it support external 4MB(or above) SPIRAM.

Thanks for this, solved my flickering neopixels on ESP32.

@tech-shubham, @vjdw Any chance that you can share a compiled version of the firmware that you got working? 🙏 Or even better, share instructions of what changes are necessary to build...

Sorry @martinjo, I'm only using a short strip and so all I needed was the original pixels.py gist. Maybe @tech-shubham can help with the firmware.