111, 112 Backlight handling improve

[hijae]

I made the lowest brightness of the backlight change depending on the device, and also modified the brightness slider to have 8 levels.
#111 Backlight timeout brightness is hardcoded and too high and #112 Backlight menu slider needs tweaking.

The name of the board is referenced here.( https://docs.m5stack.com/en/arduino/m5unified/m5unified_appendix )

[gkoh]

This mostly looks very good @hijae. For the devices I have tested (M5StickC, M5StickC-Plus, M5StickC-Plus2) the inactivity brightness as chosen works well, quite dim, but still visible.

I have one comment to be fixed.

[gkoh]

@hijae That's improved, but differently.

Minimum brightness is now zero on the progress bar, this is good.

However, for M5StickC[Plus], the progress bar still does not reach near maximum, there is a sizeable gap.
You can reproduce this on a M5StickC-Plus2 by changing _MinimumBrightness to 48.

Perhaps it will be a lot cleaner if we define const uint8_t _MaxSteps = 8 and use that as a step counter in the loop.
This will allow us to:

• be clearer about the roll over check (ie. rather than brightness < 255, we have step < _MaxSteps)
• allow easy change of steps later (eg. change to 4 or 40)
• perfectly calculate the progress bar percentage
  • float p = (step/(_MaxSteps - 1)) * 100.0f;
• use p to calculate the brightness
  • _brightness = (uint8_t)(2.55 * p);

[hijae]

I took your advice and fixed it. 1faf893

[gkoh]

I took your advice and fixed it. 1faf893

Well done, works as expected on all devices now.
Thank you very much for your patience!