enable non-PWM pins for backlight color, add kattni's pi-specific simpletest

[brennen]

Rationale: pulseio isn't available on CPython Linux systems (i.e. the Pi), this mimics the design of the original Adafruit_Python_CharLCD.

Adds enable_pwm parameter (defaults to True) to Character_LCD_RGB constructor, and conditionalizes handling of the color pins on this value. If PWM is disabled, pins should be DigitalInOut instances.

It's entirely possible I've messed something up here, so close review is appreciated.

[ladyada]

rather than enabling pwm, check the attrs?

[brennen]

yeah, i wasn't super comfortable with the enable_pwm thing, but i'm also not sure what the idiomatic thing to do is here - isinstance on the pin objects? still feels sort of hacky...

[ladyada]

i know kattni's done a lot more of this with analog/pwm pins - i'll defer to her wisdom :D

[kattni]

I'm not super keen on this setup. We've discussed a couple of options such as creating a subclass for non-pwm pins or checking the object types (which also isn't great). Adding CircuitPython LIbrarians.

[caternuson]

Why no love for isinstance? Seems like an OK way to me.

[brennen]

i've gotten a "that's how you do that but you shouldn't want to do that" vibe every time i've googled this in the past, but if it doesn't raise alarm bells for people more steeped in Python Aesthetic than i am, i'll just go that route. threading a bunch of logic around that sort of type check can get weird, but i guess we're not dealing with all that complex a piece of code here...

[sommersoft]

I would say isinstance() too. Additionally, even if enable_pwm was kept, I would still check the objects to make sure they matched expected behavior (even though set_color() would still raise an exception).

[brennen]

wrote the isinstance() version, then did a bit more googling and realized what ladyada meant about checking the attrs.

[caternuson]

I like it. Do you need the check in __init__ at all? Just set direction to OUTPUT. The check in set_color takes care of it from there.

[brennen]

Do you need the check in init at all?

yeah, it at least needs to discern there between being a DigitalInOut or a PWMOut, since the latter doesn't have direction.

[tannewt]

Super minor but this can be:

elif not hasattr(pin, 'duty_cycle'):

[tannewt]

hasattr looks good to me. 👍

[kattni]

Thanks for the input everyone! Looks great!