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Allow backlight duty cycle limit #10260

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Oct 23, 2020
Merged

Allow backlight duty cycle limit #10260

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17 changes: 9 additions & 8 deletions docs/feature_backlight.md
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Expand Up @@ -62,14 +62,15 @@ Valid driver values are `pwm`, `software`, `custom` or `no`. See below for help

To configure the backlighting, `#define` these in your `config.h`:

|Define |Default |Description |
|---------------------|-------------|-------------------------------------------------------------------------------------|
|`BACKLIGHT_PIN` |*Not defined*|The pin that controls the LED(s) |
|`BACKLIGHT_LEVELS` |`3` |The number of brightness levels (maximum 31 excluding off) |
|`BACKLIGHT_CAPS_LOCK`|*Not defined*|Enable Caps Lock indicator using backlight (for keyboards without dedicated LED) |
|`BACKLIGHT_BREATHING`|*Not defined*|Enable backlight breathing, if supported |
|`BREATHING_PERIOD` |`6` |The length of one backlight "breath" in seconds |
|`BACKLIGHT_ON_STATE` |`1` |The state of the backlight pin when the backlight is "on" - `1` for high, `0` for low|
| Define | Default | Description |
|------------------------|---------------|-------------------------------------------------------------------------------------------------------------------|
| `BACKLIGHT_PIN` | *Not defined* | The pin that controls the LED(s) |
| `BACKLIGHT_LEVELS` | `3` | The number of brightness levels (maximum 31 excluding off) |
| `BACKLIGHT_CAPS_LOCK` | *Not defined* | Enable Caps Lock indicator using backlight (for keyboards without dedicated LED) |
| `BACKLIGHT_BREATHING` | *Not defined* | Enable backlight breathing, if supported |
| `BREATHING_PERIOD` | `6` | The length of one backlight "breath" in seconds |
| `BACKLIGHT_ON_STATE` | `1` | The state of the backlight pin when the backlight is "on" - `1` for high, `0` for low |
| `BACKLIGHT_LIMIT_VAL ` | `255` | The maximum duty cycle of the backlight -- `255` allows for full brightness, any lower will decrease the maximum. |

Unless you are designing your own keyboard, you generally should not need to change the `BACKLIGHT_PIN` or `BACKLIGHT_ON_STATE`.

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14 changes: 12 additions & 2 deletions quantum/backlight/backlight_avr.c
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Expand Up @@ -3,6 +3,11 @@
#include "backlight_driver_common.h"
#include "debug.h"

// Maximum duty cycle limit
#ifndef BACKLIGHT_LIMIT_VAL
# define BACKLIGHT_LIMIT_VAL 255
#endif

// This logic is a bit complex, we support 3 setups:
//
// 1. Hardware PWM when backlight is wired to a PWM pin.
Expand Down Expand Up @@ -240,6 +245,11 @@ static uint16_t cie_lightness(uint16_t v) {
}
}

// rescale the supplied backlight value to be in terms of the value limit
static uint32_t rescale_limit_val(uint32_t val) {
return (val * (BACKLIGHT_LIMIT_VAL + 1)) / 256;
}

// range for val is [0..TIMER_TOP]. PWM pin is high while the timer count is below val.
static inline void set_pwm(uint16_t val) { OCRxx = val; }

Expand Down Expand Up @@ -269,7 +279,7 @@ void backlight_set(uint8_t level) {
#endif
}
// Set the brightness
set_pwm(cie_lightness(TIMER_TOP * (uint32_t)level / BACKLIGHT_LEVELS));
set_pwm(cie_lightness(rescale_limit_val(TIMER_TOP * (uint32_t)level / BACKLIGHT_LEVELS)));
}

void backlight_task(void) {}
Expand Down Expand Up @@ -375,7 +385,7 @@ ISR(TIMERx_OVF_vect)
breathing_interrupt_disable();
}

set_pwm(cie_lightness(scale_backlight((uint16_t)pgm_read_byte(&breathing_table[index]) * 0x0101U)));
set_pwm(cie_lightness(rescale_limit_val(scale_backlight((uint16_t)pgm_read_byte(&breathing_table[index]) * 0x0101U))));
}

#endif // BACKLIGHT_BREATHING
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14 changes: 12 additions & 2 deletions quantum/backlight/backlight_chibios.c
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Expand Up @@ -3,6 +3,11 @@
#include <hal.h>
#include "debug.h"

// Maximum duty cycle limit
#ifndef BACKLIGHT_LIMIT_VAL
# define BACKLIGHT_LIMIT_VAL 255
#endif

// GPIOV2 && GPIOV3
#ifndef BACKLIGHT_PAL_MODE
# define BACKLIGHT_PAL_MODE 2
Expand Down Expand Up @@ -58,6 +63,11 @@ static uint16_t cie_lightness(uint16_t v) {
}
}

static uint32_t rescale_limit_val(uint32_t val) {
// rescale the supplied backlight value to be in terms of the value limit
return (val * (BACKLIGHT_LIMIT_VAL + 1)) / 256;
}

void backlight_init_ports(void) {
#ifdef USE_GPIOV1
palSetPadMode(PAL_PORT(BACKLIGHT_PIN), PAL_PAD(BACKLIGHT_PIN), PAL_MODE_STM32_ALTERNATE_PUSHPULL);
Expand Down Expand Up @@ -85,7 +95,7 @@ void backlight_set(uint8_t level) {
pwmDisableChannel(&BACKLIGHT_PWM_DRIVER, BACKLIGHT_PWM_CHANNEL - 1);
} else {
// Turn backlight on
uint32_t duty = (uint32_t)(cie_lightness(0xFFFF * (uint32_t)level / BACKLIGHT_LEVELS));
uint32_t duty = (uint32_t)(cie_lightness(rescale_limit_val(0xFFFF * (uint32_t)level / BACKLIGHT_LEVELS)));
pwmEnableChannel(&BACKLIGHT_PWM_DRIVER, BACKLIGHT_PWM_CHANNEL - 1, PWM_FRACTION_TO_WIDTH(&BACKLIGHT_PWM_DRIVER, 0xFFFF, duty));
}
}
Expand Down Expand Up @@ -129,7 +139,7 @@ void breathing_callback(PWMDriver *pwmp) {
static uint16_t breathing_counter = 0;
breathing_counter = (breathing_counter + 1) % (breathing_period * 256);
uint8_t index = breathing_counter / interval % BREATHING_STEPS;
uint32_t duty = cie_lightness(scale_backlight(breathing_table[index] * 256));
uint32_t duty = cie_lightness(rescale_limit_val(scale_backlight(breathing_table[index] * 256)));

chSysLockFromISR();
pwmEnableChannelI(pwmp, BACKLIGHT_PWM_CHANNEL - 1, PWM_FRACTION_TO_WIDTH(&BACKLIGHT_PWM_DRIVER, 0xFFFF, duty));
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