Add optional LED buffering

[PaintYourDragon]

This PR adds a buffering capability that can optionally be enabled via constructor. A “buffered” IS31FL3741 has LED PWM state stored in RAM, pushed to the chip only when show() is called. This can provide smoother and faster animation, in exchange for a little over 1/3 K of RAM, and having to periodically call show(). Inspired by similar additions to the Arduino version of this library.

This currently only covers the LED glasses. Support for the QT RGB matrix and the eval board will be added tomorrow, when I’ve had some time to test. (Edit: I think these pick up the change automatically, since there’s no extra constructor as with the glasses…still need to change imports to get those constants though.)

Default behavior is to work as originally written; LEDs are unbuffered. Enabling buffering requires some changes to import statements and arguments to constructors. See the LED glasses rings example.

import adafruit_is31fl3741
glasses = LED_Glasses(board.I2C(), allocate=adafruit_is31fl3741.MUST_BUFFER)
…
glasses.show()

The optional “allocate” argument can have one of three values, declared in adafruit_is31fl3741:

• NO_BUFFER : LED data is NOT buffered; pixels are written with each drawing request. This is the default behavior if unspecified. show() can still be called but has no effect.
• PREFER_BUFFER : LED data is buffered if RAM permits. If allocation fails, program continues with the LEDs unbuffered…not as smooth, but at least it’s running.
• MUST_BUFFER : If the LED data can’t be buffered due to limited RAM, the constructor throws a MemoryError exception. “Go big or go home.”

Additionally, this fixes a small math error that caused the glasses rings example to have occasional speckles.

[github-actions]

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[ladyada]

nice!