Add/update DotStar single LED template code

[kattni]

Tested on ItsyBitsy M4.

[PaintYourDragon]

With a single LED and with auto_write being the default case, would it be OK to replace:

        for led in range(1):
             dot_index = (led * 256 // 1) + color_value
             dot[led] = colorwheel(dot_index & 255)
         dot.show()

with:

        dot[0] = colorwheel(color_value)

?

Sometimes there’s Learning Value in showing things the verbose way, so no worries if that was the intent.

[kattni]

@PaintYourDragon Ooh, this is good. I don't need it to be verbose. I will need to update the copy to match it, but it means less copy. In this case, it's simply meant to give rainbows, not necessarily explain how rainbows work deep down. To be clear, you're saying the function should look like this? Or am I missing part of your suggestion?

def rainbow(delay):
    for color_value in range(255):
        dot[0] = colorwheel(color_value)
        dot.show()
        time.sleep(delay)

This does work, but you might have meant something slightly different that could be better.

[PaintYourDragon]

Yep. All the math just distills down to nothing in that case and color_value can be passed straight to colorwheel. And the show() call might be redundant.

[kattni]

Wait - I just figured out what I was missing. I never set auto_write=False. Removing the show()!