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Made AVR backlight pwm resolution configurable (#7521) 

* Made static backlight pwm resolution configurable

* Made breathing backlighting configurable too

* Finished my ifdef

* Ran clang-format

* Added missing semi-colon

* Solved weird behaviour by right-shifting the right amount

* Made breathing period scaled on actual pwm frequency

* Made the low end deadzone scaled on the top value

* Moved 'pwm_frequency' declaration outside ifdef

* Fixed 'never used' error

* Fixed 'never used' error

* Fixed breathing ISR to 120Hz

* Removed pwm_frequency constant
Constant is no longer needed since running the breathing ISR at a fixed 120Hz

* Re-add brightness limiting

* re-introduce scaling
master
Mikkel Jeppesen 2021-11-17 21:56:13 +01:00 committed by GitHub
parent 121a2e0f07
commit e0a5056963
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 68 additions and 41 deletions
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109
quantum/backlight/backlight_avr.c
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@ -199,13 +199,14 @@ static inline void disable_pwm(void) {
// reaches the backlight level, where we turn off the LEDs,
// but also an overflow interrupt when the counter rolls back to 0,
// in which we're going to turn on the LEDs.
// The LED will then be on for OCRxx/0xFFFF time, adjusted every 244Hz.
// The LED will then be on for OCRxx/0xFFFF time, adjusted every 244Hz,
// or F_CPU/BACKLIGHT_CUSTOM_RESOLUTION if used.
// Triggered when the counter reaches the OCRx value
ISR(TIMERx_COMPA_vect) { backlight_pins_off(); }
// Triggered when the counter reaches the TOP value
// this one triggers at F_CPU/65536 =~ 244 Hz
// this one triggers at F_CPU/ICRx = 16MHz/65536 =~ 244 Hz
ISR(TIMERx_OVF_vect) {
# ifdef BACKLIGHT_BREATHING
if (is_breathing()) {
@ -220,8 +221,8 @@ ISR(TIMERx_OVF_vect) {
// artifacts (especially while breathing, because breathing_task
// takes many computation cycles).
// so better not turn them on while the counter TOP is very low.
if (OCRxx > 256) {
backlight_pins_on();
if (OCRxx > ICRx / 250 + 5) {
FOR_EACH_LED(backlight_on(backlight_pin);)
}
}
@ -231,24 +232,26 @@ ISR(TIMERx_OVF_vect) {
// See http://jared.geek.nz/2013/feb/linear-led-pwm
static uint16_t cie_lightness(uint16_t v) {
if (v <= 5243) // if below 8% of max
return v / 9; // same as dividing by 900%
else {
uint32_t y = (((uint32_t)v + 10486) << 8) / (10486 + 0xFFFFUL); // add 16% of max and compare
// to get a useful result with integer division, we shift left in the expression above
// and revert what we've done again after squaring.
y = y * y * y >> 8;
if (y > 0xFFFFUL) // prevent overflow
return 0xFFFFU;
else
return (uint16_t)y;
if (v <= ICRx / 12) // If the value is less than or equal to ~8% of max
{
return v / 9; // Same as dividing by 900%
} else {
// In the next two lines values are bit-shifted. This is to avoid loosing decimals in integer math.
uint32_t y = (((uint32_t)v + ICRx / 6) << 5) / (ICRx / 6 + ICRx); // If above 8%, add ~16% of max, and normalize with (max + ~16% max)
uint32_t out = (y * y * y * ICRx) >> 15; // Cube it and undo the bit-shifting. (which is now three times as much due to the cubing)
if (out > ICRx) // Avoid overflows
{
out = ICRx;
}
return out;
}
}
// rescale the supplied backlight value to be in terms of the value limit
// rescale the supplied backlight value to be in terms of the value limit // range for val is [0..ICRx]. PWM pin is high while the timer count is below val.
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.
// range for val is [0..ICRx]. PWM pin is high while the timer count is below val.
static inline void set_pwm(uint16_t val) { OCRxx = val; }
void backlight_set(uint8_t level) {
@ -277,7 +280,7 @@ void backlight_set(uint8_t level) {
#endif
}
// Set the brightness
set_pwm(cie_lightness(rescale_limit_val(TIMER_TOP * (uint32_t)level / BACKLIGHT_LEVELS)));
set_pwm(cie_lightness(rescale_limit_val(ICRx * (uint32_t)level / BACKLIGHT_LEVELS)));
}
void backlight_task(void) {}
@ -292,6 +295,11 @@ void backlight_task(void) {}
static uint8_t breathing_halt = BREATHING_NO_HALT;
static uint16_t breathing_counter = 0;
static uint8_t breath_scale_counter = 1;
/* Run the breathing loop at ~120Hz*/
const uint8_t breathing_ISR_frequency = 120;
static uint16_t breathing_freq_scale_factor = 2;
# ifdef BACKLIGHT_PWM_TIMER
static bool breathing = false;
@ -319,14 +327,14 @@ bool is_breathing(void) { return !!(TIMSKx & _BV(TOIEx)); }
} while (0)
# endif
# define breathing_min() \
do { \
breathing_counter = 0; \
} while (0)
# define breathing_max() \
do { \
breathing_counter = get_breathing_period() * 244 / 2; \
} while (0)
# define breathing_min() \
do { \
breathing_counter = 0; \
} while (0)
# define breathing_max() \
do { \
breathing_counter = breathing_period * breathing_ISR_frequency / 2; \
} while (0)
void breathing_enable(void) {
breathing_counter = 0;
@ -369,21 +377,33 @@ void breathing_task(void)
# else
/* Assuming a 16MHz CPU clock and a timer that resets at 64k (ICR1), the following interrupt handler will run
* about 244 times per second.
*
* The following ISR runs at F_CPU/ISRx. With a 16MHz clock and default pwm resolution, that means 244Hz
*/
ISR(TIMERx_OVF_vect)
# endif
{
uint8_t breathing_period = get_breathing_period();
uint16_t interval = (uint16_t)breathing_period * 244 / BREATHING_STEPS;
// Only run this ISR at ~120 Hz
if(breath_scale_counter++ == breathing_freq_scale_factor)
{
breath_scale_counter = 1;
}
else
{
return;
}
uint16_t interval = (uint16_t)breathing_period * breathing_ISR_frequency / BREATHING_STEPS;
// resetting after one period to prevent ugly reset at overflow.
breathing_counter = (breathing_counter + 1) % (breathing_period * 244);
uint8_t index = breathing_counter / interval % BREATHING_STEPS;
breathing_counter = (breathing_counter + 1) % (breathing_period * breathing_ISR_frequency);
uint8_t index = breathing_counter / interval % BREATHING_STEPS;
if (((breathing_halt == BREATHING_HALT_ON) && (index == BREATHING_STEPS / 2)) || ((breathing_halt == BREATHING_HALT_OFF) && (index == BREATHING_STEPS - 1))) {
breathing_interrupt_disable();
}
set_pwm(cie_lightness(rescale_limit_val(scale_backlight((uint16_t)pgm_read_byte(&breathing_table[index]) * 0x0101U))));
// Set PWM to a brightnessvalue scaled to the configured resolution
set_pwm(cie_lightness(rescale_limit_val(scale_backlight((uint16_t)pgm_read_byte(&breathing_table[index]) * ICRx / 255))));
}
#endif // BACKLIGHT_BREATHING
@ -413,16 +433,23 @@ void backlight_init_ports(void) {
"In fast PWM mode, the compare units allow generation of PWM waveforms on the OCnx pins. Setting the COMnx1:0 bits to two will produce a non-inverted PWM [..]."
"In fast PWM mode the counter is incremented until the counter value matches either one of the fixed values 0x00FF, 0x01FF, or 0x03FF (WGMn3:0 = 5, 6, or 7), the value in ICRn (WGMn3:0 = 14), or the value in OCRnA (WGMn3:0 = 15)."
*/
# if BACKLIGHT_ON_STATE == 1
TCCRxA = _BV(COMxx1) | _BV(WGM11);
# else
TCCRxA = _BV(COMxx1) | _BV(COMxx0) | _BV(WGM11);
# endif
TCCRxA = _BV(COMxx1) | _BV(WGM11); // = 0b00001010;
TCCRxB = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
# endif
TCCRxB = _BV(WGM13) | _BV(WGM12) | _BV(CS10);
#endif
// Use full 16-bit resolution. Counter counts to ICR1 before reset to 0.
ICRx = TIMER_TOP;
# ifdef BACKLIGHT_CUSTOM_RESOLUTION
# if (BACKLIGHT_CUSTOM_RESOLUTION > 0xFFFF || BACKLIGHT_CUSTOM_RESOLUTION < 1)
# error "This out of range of the timer capabilities"
# elif (BACKLIGHT_CUSTOM_RESOLUTION < 0xFF)
# warning "Resolution lower than 0xFF isn't recommended"
# endif
# ifdef BACKLIGHT_BREATHING
breathing_freq_scale_factor = F_CPU / BACKLIGHT_CUSTOM_RESOLUTION / 120;
# endif
ICRx = BACKLIGHT_CUSTOM_RESOLUTION;
# else
ICRx = TIMER_TOP;
# endif
backlight_init();
#ifdef BACKLIGHT_BREATHING
@ -430,4 +457,4 @@ void backlight_init_ports(void) {
breathing_enable();
}
#endif
}
}