MicroZed Chronicles リスト http://adiuvoengineering.com/?page_id=285
@ Adam Taylor blog
https://forums.xilinx.com/t5/Xcell-Daily-Blog/Adam-Taylor-s-MicroZed-Chronicles-Part-34-Driving-Adafruit-RGB/ba-p/466228
NeoPixelの駆動に25bit shift registerが必要な理由は以下のように記載されていた。
A 1.25µsec bit time clocked out at 50nsec per clock tick means that we’ll need a 25-bit shift register, which matches the code snippet shown above.
1.25 usec = 1250 nsec
1250 nsec / 50nsec = 25
25回で送出するためという理由。NeoPixelが24bitの色情報を持つのとは関係なさそうだ。
1.25usecというのは以下で決めている
The overall waveform periods for a one or a zero differ as well. The specification calls for periods of 1.15µsec for a zero and 1.3µsec for a one. However, the NeoPixel’s overall bit-time tolerance is ±300nsec, so we can use a 1.25µsec time period for both one and zero waveforms and still meet specified timing.