Driving more than 5 pixels on a orange pi zero

[melazarus]

I'm experiencing some issues when driving 6 or more pixels.

It seems that the SPI lib or hardware inserts a small delay of 5µs eacht 60-70 bytes transferred. screenshot

I don't think this is an issue with the ws2812-spi lib but I'm hoping anyone here has some clue of what may be happening here.

thanks

[pietrodn]

I have the same problem on a NanoPi Air, which uses the Allwinner H3 CPU. It works fine up to 5 pixels, but when I use 6 pixels or more, all of them start flickering.

[pietrodn]

I solved this problem by replacing the spi.xfer() call with spi.writebytes() and applying the tweak in #2. Now I am able to drive more than 90 LEDs on the NanoPi Air: they are stable and without any problem.

Code:

# Initialize SPI with the correct frequency
spi = spidev.SpiDev()
spi.open(0, 0)
spi.max_speed_hz = int(4/1.05e-6)

def write2812(spi, colors):
       # Optimized version of the `write2812_pylist4` function at:
       # https://github.com/joosteto/ws2812-spi/blob/master/ws2812.py
       # with this fix (0x00 at the beginning): https://github.com/joosteto/ws2812-spi/issues/2
       tx = [0x00] + [
           ((byte >> (2 * ibit + 1)) & 1) * 0x60 +
           ((byte >> (2 * ibit + 0)) & 1) * 0x06 +
           0x88
           for rgb in colors
           for byte in (rgb.g, rgb.r, rgb.b)  # the LED strip is GRB
           for ibit in range(3, -1, -1)
       ]

       # Using xfer() or xfer2() in place of writebytes() causes the LEDs to flicker after the 5th one
       # reports of this bug:
       # 1) https://github.com/doceme/py-spidev/issues/72
       # 2) https://github.com/joosteto/ws2812-spi/issues/6
       spi.writebytes(tx)

[bogdanvb]

Solving the problem with the first LED when controlling ws2812 via spi on nanopi neo.

Thanks to your help, I came up with a code so that the first LED (ws2812) on Nanopi neo would work correctly and not turn green. This code reduces the length of the first bit of data to a normal value. Code:

import spidev
import ws2812
import time

# Initialize SPI with the correct frequency
spi = spidev.SpiDev()
spi.open(0, 0)
spi.max_speed_hz = int(4/1.05e-6)

def write2812(spi, colors):
       # Optimized version of the `write2812_pylist4` function at:
       # https://github.com/joosteto/ws2812-spi/blob/master/ws2812.py
       # with this fix (0x00 at the beginning): https://github.com/joosteto/ws2812-spi/issues/2
       tx = [0x00] + [
           ((byte >> (2 * ibit + 1)) & 1) * 0x60 +
           ((byte >> (2 * ibit + 0)) & 1) * 0x06 +
           0x88
           for rgb in colors
           for byte in (rgb[0], rgb[1], rgb[2])  # the LED strip is GRB
           for ibit in range(3, -1, -1)
       ]

       # Using xfer() or xfer2() in place of writebytes() causes the LEDs to flicker after the 5th one
       # reports of this bug:
       # 1) https://github.com/doceme/py-spidev/issues/72
       # 2) https://github.com/joosteto/ws2812-spi/issues/6
       
       #spi.writebytes(tx)
       spi.xfer(tx)

                # three diods
write2812(spi, [[0,10,0], [0,10,0], [0, 10, 0]])
time.sleep(0.5)

write2812(spi, [[100,0,0], [100,0,0], [100, 0, 0]])
time.sleep(0.5)

write2812(spi, [[0,0,10], [0,0,10], [0, 0, 10]])
time.sleep(0.5)

write2812(spi, [[0,0,0], [0,0,0], [0, 0, 0]])