Display-O-Tron backlight toggle using Buttonshim


I’m trying to create a toggle switch for the backlight of the DotHat using the ButtonShim.

I tried several things :

  • a toggle variable set to True and check with an if statement.
  • a for r, g, b in backlight.rgb(r, g, b)…

This is my last try :

def button_a(button, pressed,):
r, g, b = backlight.rgb(r, g, b)
if r > 0 or g > 0 or b > 0:
else :
backlight.rgb(255, 42, 255)

Sometimes i can turn off the backlight but never set an rgb value when it is off…

Does someone have an idea how to solve this ?

Thanks. :)


The r, g, b = backlight.rgb(r, g, b) line wont accomplish anything, since rgb doesn’t return a value.

Internally the Display-o-Tron backlight is 19 individual LEDs, with no concept of an RGB colour that applies to them all.

So you should either keep track of the r, g and b values yourself, or the on/off state or perhaps even both.

r, g, b, on = 255, 42, 255, True
def button_a(button, pressed):
    global on
    on = not on
    backlight.rgb(r * on, g * on, b * on)

It’s a naughty thing to rely upon, but Python will silently treat “True” and “False” as 1 and 0 for the purpose of mathematical operations, so:

>>> 42 * False
>>> 42 * True

The above would mean your r, g, b backlight colour and the on/off state are separate properties so you can change the r, g, b elsewhere and toggle the backlight on/off.

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Thank you Phil, you truly deserves that exquisite moustache of yours. ;)

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Haha :D you’re welcome!

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