WS2812 datasheet(75/98 Pages) RASPBERRY-PI

75 / 98 page

How fast can I refresh a string of (N) pixels?

NeoPixels receive data from a fixed-frequency 800 KHz datastream (except for “V1” Flora pixels, which use 400

KHz). Each bit of data therefore requires 1/800,000 sec — 1.25 microseconds. One pixel requires 24 bits (8 bits each

for red, green blue) — 30 microseconds. After the last pixel’s worth of data is issued, the stream must stop for at

least 50 microseconds for the new colors to “latch.”

For a strip of 100 pixels, that’s (100 * 30) + 50, or 3,050 microseconds. 1,000,000 / 3,050 = 328 updates per second,

approximately.

However…

That’s

only the time needed to push the bits down the wire. The actual refresh rate will be something less than this,

and can’t be estimated as a single number for all cases. It takes time to process each “frame” of animation. How

much time depends on the complexity of the math and the efficiency of the code (for example, floating-point

calculations can be relatively slow). The formula above gives a maximum

theoretical rate, but that’s just a starting

point. Reality in some cases could fall an order of magnitude (or more) below this.

For exploratory benchmarking, you can always write code

as if a large number of pixels were present, and time the

result. The extra output bits will simply be ignored by the strip (or you can even test with no NeoPixels connected at

all).

https://learn.adafruit.com/adafruit-neopixel-uberguide

Page 78 of 101

WS2812 bảng dữ liệu(PDF) 75 Page - Raspberry Pi Holdings PLC