diff options
Diffstat (limited to 'quantum/backlight/backlight_avr.c')
| -rw-r--r-- | quantum/backlight/backlight_avr.c | 88 | 
1 files changed, 56 insertions, 32 deletions
| diff --git a/quantum/backlight/backlight_avr.c b/quantum/backlight/backlight_avr.c index e47192de34..67b551dc3c 100644 --- a/quantum/backlight/backlight_avr.c +++ b/quantum/backlight/backlight_avr.c @@ -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()) { @@ -220,7 +221,7 @@ 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) { +    if (OCRxx > ICRx / 250 + 5) {          backlight_pins_on();      }  } @@ -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; @@ -323,9 +331,9 @@ bool is_breathing(void) { return !!(TIMSKx & _BV(TOIEx)); }          do {                       \              breathing_counter = 0; \          } while (0) -#    define breathing_max()                                       \ -        do {                                                      \ -            breathing_counter = get_breathing_period() * 244 / 2; \ +#    define breathing_max()                                                           \ +        do {                                                                          \ +            breathing_counter = get_breathing_period() * breathing_ISR_frequency / 2; \          } while (0)  void breathing_enable(void) { @@ -369,21 +377,30 @@ 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)get_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); +    breathing_counter = (breathing_counter + 1) % (get_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 +430,23 @@ 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 - -    TCCRxB = _BV(WGM13) | _BV(WGM12) | _BV(CS10); +    TCCRxA = _BV(COMxx1) | _BV(WGM11);             // = 0b00001010; +    TCCRxB = _BV(WGM13) | _BV(WGM12) | _BV(CS10);  // = 0b00011001;  #endif -    // Use full 16-bit resolution. Counter counts to ICR1 before reset to 0. + +#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 | 
