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Jan-Erik Soderholm <jan-erik.soderholm@telia.com> writes:
>>>> One stupid moment, the datasheet calls out the order of colors as GRB,
>>>> which is how I made the data structure. What I forgot was that they
>>>> are talking about transmission order, and they are MSB first. So it
>>>> actually needed to be BRG.
>>
>> is saying the same as
>>
>>> What could be a question about significance is the order
>>> the individual bits or each color is sent. *That* could
>>> be MSb or LSb (Most/Least Significant bit) first. :-)
>>
>> AFAICS.
>>
>
> No, it doesn't. The order by which the *colors* are sent has
> nothing to do with significans, it is just a design choice.
> All three colors are equaly significant as such!
>
> The order how each *bit* of *each color* is sent has everything
> to do with (bit) significance.

Well, yes, that's true. But consider a data sheet that says (with my
beautiful ascii art)

"
      |  RED      |  GREEN     |  BLUE     |=20
      \------------------------------------/
  Bit  23       16 15         8 7         0

Data is MSB first

"

Not a model of clarity, maybe, but it does make sense. Conceptually the
data sheet author has thought of the three colours embedded into some 24
bit number. Maybe the product can transmit other data, also in 24 (or
32?) bit packages.

Then the author says "Oh, and data comes out MSB first".

This isn't just hypothetical: I've used such datasheets (and such
network protocol documentation).

Even more confusing is when the data gets sent little-endian by byte (so
you'd get blue, green, red but each byte from MSB to LSB). I recently
spent some time trying to get my head around an overly clever DMA block
that could switch endian-ness when so configured. Very easy to get
wrong!


Rupert

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