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