How to get neopixel work for different format or using PWM

[ujur007]

I have a RGB LED that is different from ws2812. It has 16 bits data for each pixel.
I am trying the PWM module from micro python to get it working but it seems not working.
I am trying to change the duty cycle dynamically, but seems it is not working.
Anyone has an idea how to do this with micropython?

pwm.init()

for j in range(3):
    for i in range(48):        
        if(((color >> i) & 0x01) == 0x01):
            pwm.duty_u16(16383*3)
        else:
            pwm.duty_u16(16383)           
            
pwm.deinit()

[robert-hh]

Can you tell us the model of the RGB led and the MCU type of your board, like ESP32, RPi Pico, ....? Then people may be able to help.
PWM does not work. It switches too slow.

[robert-hh]

You can use machine.bitstream(), which is used by the NeoPixel driver as well which just issues H/L state changes defined by a timing tuple.

[ujur007]

Hi, I am using Wurth Elecktronik LED.
https://www.we-online.com/components/products/datasheet/1312121320437.pdf
Now, I have changed the code to SPI. I realized this that PWM is slow. The following code works but there is still some issue.
I am using ESP32s3

`from machine import PWM
import machine
import sys
import time

spi = machine.SPI(2, baudrate=7000000, polarity=0, phase=0, sck=machine.Pin(40), mosi=machine.Pin(13), miso=machine.Pin(38))


def convert_data():
    red = 0x0000
    green = 0x0000
    blue = 0xFFFF
    color = red << 32 | green << 16 | blue
    
    for j in range(3):
        data = bytes()
        for i in range(48):
            if((color >> i) & 0x1):
                data = data + bytes(b'11111100')                       
            else:
                data = data + bytes(b'11000000')
            return data
            
buf = convert_data()
spi.write(buf)
time.sleep_us(50)

        `

[dhalbert]

PIO on RP2040 or RP2350 would also be a good way to support this.

[ujur007]

Yes, might be. But I have ESP32

[GitHubsSilverBullet]

I have a RGB LED that is different from ws2812. It has 16 bits data for each pixel.

So it's capable of displaying 281 Trillion colours?
That'd be very impressive!

[ujur007]

Hi, not really. But the 12-bits are there for each color. and four bits are for gain.

[GitHubsSilverBullet]

Maybe this will work:

#!micropython
# -*- coding: UTF-8 -*-
# vim:fileencoding=UTF-8:ts=4
from machine import bitstream
from struct import pack

gain = 15
level = 2**12-1
data = pack('>3H', (gain<<12)+level, (gain<<12)+level, (gain<<12)+level)
sig = (300, 900, 900, 300)
bitstream(23, 0, sig, data)

Oh, one more thing … Keep in mind that – according to the datasheet – it needs a level converter when operated from a 3.3V µC.

[robert-hh]

Keep in mind that – according to the datasheet – it needs a level converter when operated from a 3.3V µC.

That is the usual problem with the Neopixel as well. The LEDs need >3.3V for a reliable operation of the blue LED. One (dirty) trick to avoid the level shift is to lower the VDD of the RGB Led, e.g. with a silicon diode. That will drop the voltage from 5V to about 4.3V. Otherwise you will need a FAST level converter, like the txb101.

The bistream() example above should work and is the best way to deal with it. Using the SPI MOSI as shown should work too, but uses a lot of memory. With the ESP32 the RMT unit would be dedicated to that task, but there is not MicroPython API yet. The PyCom port had RMT support, but that was never ported for ESP32Sx.

[GitHubsSilverBullet]

One (dirty) trick to avoid the level shift is to lower the VDD of the RGB Led, e.g. with a silicon diode. That will drop the voltage from 5V to about 4.3V.

Yes, but only if a significant current flows.

Should the µC have 5V tolerant OC outputs, one could generate the inverted signal and use an OC output with a pull-up to 5V.

[ujur007]

I have level converter that is working as it should. It is this -- TXS0108EPWR

[ujur007]

I have level converter and everything setup. I am using SPI interface with 3Mhz frequency. This would create some 0.3us bit.
As you can see in the code below. For 1 I am using 1110 and for 0 I am using 1000.
I collect all these buts in data variable and send them over SPI interface.
Unfortunately, LEDS are lit but it is not perfect. colors are meshed up

from machine import PWM
import machine
import sys
import time

spi = machine.SPI(2, baudrate=3000000, polarity=0, phase=0, sck=machine.Pin(40), mosi=machine.Pin(13), miso=machine.Pin(38))


def convert_data():
    red = 0xFFFF
    green = 0x0000
    blue = 0x0000
    color = red << 32 | green << 16 | blue
    data = bytes()
    
    for j in range(3):        
        for i in range(48):
            if((color >> i) & 0x1):
                data = data + bytes(b'1110')
            else:
                data = data + bytes(b'1000')
    return data
            
buf = convert_data()
spi.write(buf)
time.sleep_us(50)
            

[ujur007]

Ok. I am new to micropython. And I think you have found the mistake that I am making here. I will try it again.
I thought that it will just add 4-bits(nibble) to the rest of the data.

[ujur007]

But I am wondering why is that issue. I am having the following line of code and the output is just 6-bits and that is fine.

data = bytes()
data = data + bytes(b'11')
data = data + bytes(b'10')
data = data + bytes(b'10')

[robert-hh]

If you type then print(len(data)), you get 6 as result, 6 bytes.

[robert-hh]

b'11' is a 2 byte string, not 2 bits.

[ujur007]

I thought 'b' is for "binary" not "bytes"

[ujur007]

Wow amazing. Thank you everyone for your inputs. So, here is the final code that is working for 3 LEDS

from machine import PWM
import machine
import sys
import time

spi = machine.SPI(2, baudrate=8000000, polarity=0, phase=0, sck=machine.Pin(40), mosi=machine.Pin(13), miso=machine.Pin(38), firstbit=0)

def convert_data():
    red = 0xFFFF
    green = 0x0000
    blue = 0x0000
    color = red << 32 | green << 16 | blue
    data = []
    
    
    print(data)    
    for j in range(3):        
        for i in range(48):
            if((color >> i) & 0x1):
                data.append(0xFC)
            else:
                data.append(0xC0)
    return data
            
buf = convert_data()
send = bytearray(buf)
spi.write(send)
time.sleep_us(50)