[sdiy] Coloured LEDs

[Vladimir Pantelic]

On 20.02.2017 21:51, rsdio at audiobanshee.com wrote:
> 
> On Feb 20, 2017, at 12:41 PM, "Byron G. Jacquot"
> <thescum at surfree.com> wrote:
>>> So this NRZ signal can be generated with a SPI port? How is this
>>> done?
>> 
>> By clocking at 8X the bit rate, and turning each bit of output into
>> a byte that's shaped like the expected code, such as 0b11000000 and
>> 0b11111000.
> 
> You could almost get by with 4X the bit rate, but that just barely
> falls within the +/-150 ns window. 5X would be almost dead on, at
> least as good as 8X, but more difficult to calculate the code
> translation.

4x works fine

> Meanwhile, my quick scan of the data sheet leaves me with the
> impression that this chip must be fed data constantly or it will be
> reset. I suppose you could leave the data line high to avoid reset.
> If it must be fed constantly, then that's an even greater load on the
> CPU.

no, reset means that the protocol "resets", the RGB values stay put.

> Must be a really cheap part for people to put up with the strange
> communications.

in my case controlling 53 LEDs with just 2 CPU pins and very little CPU
overhead is worth it.