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backlight breathing overhaul (#2187)

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* add breathing to bananasplit

* backlight breathing overhaul

* fix the backlight_tick thing.

* fix for vision_division backlight

* fix a few keymaps and probably break breathing for some weirdly set-up boards.

* remove BL_x keycodes because they made unreasonable assumptions

* some fixes for BL keycodes

* integer cie lightness scaling

* use cie lightness for non-breathing backlight and make breathing able to reach true max brightness
This commit is contained in:
Balz Guenat 2018-01-01 23:47:51 +01:00 • committed by Jack Humbert
parent d6215ad6af
commit 4931510ad3
25 changed files with 285 additions and 329 deletions
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docs/feature_backlight.md
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@ -10,8 +10,30 @@ These keycodes control the backlight. Most keyboards use this for single color i
|---------|------------------------------------------|
|`BL_TOGG`|Turn the backlight on or off |
|`BL_STEP`|Cycle through backlight levels |
|`BL_x` |Set a specific backlight level between 0-9|
|`BL_ON` |An alias for `BL_9` |
|`BL_OFF` |An alias for `BL_0` |
|`BL_ON` |Set backlight to max brightness |
|`BL_OFF` |Turn backlight off |
|`BL_INC` |Increase backlight level |
|`BL_DEC` |Decrease backlight level |
|`BL_BRTG`|Toggle backlight breathing |
Note that for backlight breathing, you need to have `#define BACKLIGHT_BREATHING` in your config.h.
## Configuration Options in `config.h`
* `BACKLIGHT_PIN B7` defines the pin that controlls the LEDs. Unless you design your own keyboard, you don't need to set this.
* `BACKLIGHT_LEVELS 3` defines the number of brightness levels (excluding OFF).
* `BACKLIGHT_BREATHING` if defined, enables backlight breathing. Note that this is only available if `BACKLIGHT_PIN` is B5, B6 or B7.
* `BREATHING_PERIOD 6` defines the length of one backlight "breath" in seconds.
## Notes on Implementation
To change the brightness when using pins B5, B6 or B7, the PWM (Pulse Width Modulation) functionality of the on-chip timer is used.
The timer is a counter that counts up to a certain TOP value (`0xFFFF` set in ICR1) before resetting to 0.
We also set an OCR1x register.
When the counter reaches the value stored in that register, the PWM pin drops to low.
The PWM pin is pulled high again when the counter resets to 0.
Therefore, OCR1x basically sets the duty cycle of the LEDs and as such the brightness where `0` is the darkest and `0xFFFF` the brightest setting.
To enable the breathing effect, we register an interrupt handler to be called whenever the counter resets (with `ISR(TIMER1_OVF_vect)`).
In this handler, which gets called roughly 244 times per second, we compute the desired brightness using a precomputed brightness curve.
To disable breathing, we can just disable the respective interrupt vector and reset the brightness to the desired level.