Solved Backlight Dimming not working problem

[alblib]

Original implementation did not work because

1. The implementation did not respect LED driver LV52204MT chip specification. It needed to prevent to enter digital mode but keep it in pwm mode, but the original implementation did not make it go into pwm mode. Also, it had too long tick time (2ms) which is well beyond proper on-time of pwm mode and can make the chip shutdown or turn on mode.
2. As the tick was too long, it did not work in most of range (10~100), and at the value 10, it blinked so much so very unpleasant to watch. I had to shorten but not too shorten the tick time to work properly, and I also implemented PDM so make eye comfortable as well as the led driver chip misunderstand the intension.

[CLAassistant]

All committers have signed the CLA.

[alblib]

tick has to be under 50us and use pdm so led driver dont go into digital mode. I worry this can make too much load on the chip. I think this is design flaw of the giga display shield. They should use dedicated pwm pin to control the backlight.

[alblib]

Also, I implemented lightness (human perception) percentage to the set function no the pwm duty cycle for convenience. Also, we have to make sure duty percentage goes not too low, otherwise the off time becomes too long so the led driver goes into shutdown mode. Thus, this implementation is just appropriate, considering every specification we have to satisfy.

[github-actions]

Memory usage change @ 0ee8484

Board	flash	%	RAM for global variables	%
arduino:mbed_giga:giga	🔺 0 - +2192	0.0 - +0.11	🔺 0 - +16	0.0 - 0.0
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A

Click for full report table

Board	examples/backlight/SimpleBacklight flash	%	examples/backlight/SimpleBacklight RAM for global variables	%	examples/basic/ArduinoLogoDrawing flash	%	examples/basic/ArduinoLogoDrawing RAM for global variables	%	examples/basic/SimpleText flash	%	examples/basic/SimpleText RAM for global variables	%	examples/camera/display_camera flash	%	examples/camera/display_camera RAM for global variables	%	examples/gfx/geometrical-shapes flash	%	examples/gfx/geometrical-shapes RAM for global variables	%	examples/gfx/hello-world flash	%	examples/gfx/hello-world RAM for global variables	%	examples/gfx/touch-switch flash	%	examples/gfx/touch-switch RAM for global variables	%	examples/imu/accelerometer flash	%	examples/imu/accelerometer RAM for global variables	%	examples/imu/gyroscope flash	%	examples/imu/gyroscope RAM for global variables	%	examples/lvgl/bar_lvgl flash	%	examples/lvgl/bar_lvgl RAM for global variables	%	examples/lvgl/button_lvgl flash	%	examples/lvgl/button_lvgl RAM for global variables	%	examples/lvgl/check_radio_lvgl flash	%	examples/lvgl/check_radio_lvgl RAM for global variables	%	examples/lvgl/image_lvgl flash	%	examples/lvgl/image_lvgl RAM for global variables	%	examples/lvgl/imu_orientation flash	%	examples/lvgl/imu_orientation RAM for global variables	%	examples/lvgl/slider_lvgl flash	%	examples/lvgl/slider_lvgl RAM for global variables	%	examples/microphone/PDMSerialPlotter flash	%	examples/microphone/PDMSerialPlotter RAM for global variables	%	examples/rgb/SimpleRGB flash	%	examples/rgb/SimpleRGB RAM for global variables	%	examples/rgb/blink flash	%	examples/rgb/blink RAM for global variables	%
arduino:mbed_giga:giga	2192	0.11	16	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A

Click for full report CSV

Board,examples/backlight/SimpleBacklight<br>flash,%,examples/backlight/SimpleBacklight<br>RAM for global variables,%,examples/basic/ArduinoLogoDrawing<br>flash,%,examples/basic/ArduinoLogoDrawing<br>RAM for global variables,%,examples/basic/SimpleText<br>flash,%,examples/basic/SimpleText<br>RAM for global variables,%,examples/camera/display_camera<br>flash,%,examples/camera/display_camera<br>RAM for global variables,%,examples/gfx/geometrical-shapes<br>flash,%,examples/gfx/geometrical-shapes<br>RAM for global variables,%,examples/gfx/hello-world<br>flash,%,examples/gfx/hello-world<br>RAM for global variables,%,examples/gfx/touch-switch<br>flash,%,examples/gfx/touch-switch<br>RAM for global variables,%,examples/imu/accelerometer<br>flash,%,examples/imu/accelerometer<br>RAM for global variables,%,examples/imu/gyroscope<br>flash,%,examples/imu/gyroscope<br>RAM for global variables,%,examples/lvgl/bar_lvgl<br>flash,%,examples/lvgl/bar_lvgl<br>RAM for global variables,%,examples/lvgl/button_lvgl<br>flash,%,examples/lvgl/button_lvgl<br>RAM for global variables,%,examples/lvgl/check_radio_lvgl<br>flash,%,examples/lvgl/check_radio_lvgl<br>RAM for global variables,%,examples/lvgl/image_lvgl<br>flash,%,examples/lvgl/image_lvgl<br>RAM for global variables,%,examples/lvgl/imu_orientation<br>flash,%,examples/lvgl/imu_orientation<br>RAM for global variables,%,examples/lvgl/slider_lvgl<br>flash,%,examples/lvgl/slider_lvgl<br>RAM for global variables,%,examples/microphone/PDMSerialPlotter<br>flash,%,examples/microphone/PDMSerialPlotter<br>RAM for global variables,%,examples/rgb/SimpleRGB<br>flash,%,examples/rgb/SimpleRGB<br>RAM for global variables,%,examples/rgb/blink<br>flash,%,examples/rgb/blink<br>RAM for global variables,%
arduino:mbed_giga:giga,2192,0.11,16,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0
arduino:mbed_portenta:envie_m7,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A