diff options
Diffstat (limited to 'quantum/backlight/backlight_avr.c')
| -rw-r--r-- | quantum/backlight/backlight_avr.c | 109 |
1 files changed, 68 insertions, 41 deletions
diff --git a/quantum/backlight/backlight_avr.c b/quantum/backlight/backlight_avr.c index e47192de34..59050e2505 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()) { @@ -220,8 +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 -} +}
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