#include "backlight.h" #include "backlight_driver_common.h" #include "progmem.h" #include <avr/io.h> #include <avr/interrupt.h> // Maximum duty cycle limit #ifndef BACKLIGHT_LIMIT_VAL # define BACKLIGHT_LIMIT_VAL 255 #endif #ifndef BACKLIGHT_PWM_TIMER # define BACKLIGHT_PWM_TIMER 1 #endif #if BACKLIGHT_PWM_TIMER == 1 # define ICRx ICR1 # define TCCRxA TCCR1A # define TCCRxB TCCR1B # define TIMERx_COMPA_vect TIMER1_COMPA_vect # define TIMERx_OVF_vect TIMER1_OVF_vect # if defined(__AVR_ATmega32A__) // This MCU has only one TIMSK register # define TIMSKx TIMSK # else # define TIMSKx TIMSK1 # endif # define TOIEx TOIE1 # define OCIExA OCIE1A # define OCRxx OCR1A #elif BACKLIGHT_PWM_TIMER == 3 # define ICRx ICR1 # define TCCRxA TCCR3A # define TCCRxB TCCR3B # define TIMERx_COMPA_vect TIMER3_COMPA_vect # define TIMERx_OVF_vect TIMER3_OVF_vect # define TIMSKx TIMSK3 # define TOIEx TOIE3 # define OCIExA OCIE3A # define OCRxx OCR3A #else # error Invalid backlight PWM timer! #endif #ifndef BACKLIGHT_RESOLUTION # define BACKLIGHT_RESOLUTION 0xFFFFU #endif #if (BACKLIGHT_RESOLUTION > 0xFFFF || BACKLIGHT_RESOLUTION < 0x00FF) # error "Backlight resolution must be between 0x00FF and 0xFFFF" #endif #define BREATHING_SCALE_FACTOR F_CPU / BACKLIGHT_RESOLUTION / 120 // The idea of software PWM assisted by hardware timers is the following // we use the hardware timer in fast PWM mode like for hardware PWM, but // instead of letting the Output Match Comparator control the led pin // (which is not possible since the backlight is not wired to PWM pins on the // CPU), we do the LED on/off by oursleves. // The timer is setup to count up to 0xFFFF, and we set the Output Compare // register to the current 16bits backlight level (after CIE correction). // This means the CPU will trigger a compare match interrupt when the counter // 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, // or F_CPU/BACKLIGHT_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/ICRx = 16MHz/65536 =~ 244 Hz ISR(TIMERx_OVF_vect) { #ifdef BACKLIGHT_BREATHING if (is_breathing()) { breathing_task(); } #endif // for very small values of OCRxx (or backlight level) // we can't guarantee this whole code won't execute // at the same time as the compare match interrupt // which means that we might turn on the leds while // trying to turn them off, leading to flickering // 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 > ICRx / 250 + 5) { backlight_pins_on(); } } // See http://jared.geek.nz/2013/feb/linear-led-pwm static uint16_t cie_lightness(uint16_t v) { if (v <= (uint32_t)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 + (uint32_t)ICRx / 6) << 5) / ((uint32_t)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 (uint16_t)out; } } // 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..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) { if (level > BACKLIGHT_LEVELS) level = BACKLIGHT_LEVELS; if (level == 0) { if (OCRxx) { TIMSKx &= ~(_BV(OCIExA)); TIMSKx &= ~(_BV(TOIEx)); } backlight_pins_off(); } else { if (!OCRxx) { TIMSKx |= _BV(OCIExA); TIMSKx |= _BV(TOIEx); } } // Set the brightness set_pwm(cie_lightness(rescale_limit_val(ICRx * (uint32_t)level / BACKLIGHT_LEVELS))); } void backlight_task(void) {} #ifdef BACKLIGHT_BREATHING # define BREATHING_NO_HALT 0 # define BREATHING_HALT_OFF 1 # define BREATHING_HALT_ON 2 # define BREATHING_STEPS 128 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 bool breathing = false; bool is_breathing(void) { return breathing; } # define breathing_interrupt_enable() \ do { \ breathing = true; \ } while (0) # define breathing_interrupt_disable() \ do { \ breathing = false; \ } while (0) # define breathing_min() \ do { \ breathing_counter = 0; \ } while (0) # define breathing_max() \ do { \ breathing_counter = get_breathing_period() * breathing_ISR_frequency / 2; \ } while (0) void breathing_enable(void) { breathing_counter = 0; breathing_halt = BREATHING_NO_HALT; breathing_interrupt_enable(); } void breathing_pulse(void) { if (get_backlight_level() == 0) breathing_min(); else breathing_max(); breathing_halt = BREATHING_HALT_ON; breathing_interrupt_enable(); } void breathing_disable(void) { breathing_interrupt_disable(); // Restore backlight level backlight_set(get_backlight_level()); } void breathing_self_disable(void) { if (get_backlight_level() == 0) breathing_halt = BREATHING_HALT_OFF; else breathing_halt = BREATHING_HALT_ON; } /* To generate breathing curve in python: * from math import sin, pi; [int(sin(x/128.0*pi)**4*255) for x in range(128)] */ static const uint8_t breathing_table[BREATHING_STEPS] PROGMEM = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 17, 20, 24, 28, 32, 36, 41, 46, 51, 57, 63, 70, 76, 83, 91, 98, 106, 113, 121, 129, 138, 146, 154, 162, 170, 178, 185, 193, 200, 207, 213, 220, 225, 231, 235, 240, 244, 247, 250, 252, 253, 254, 255, 254, 253, 252, 250, 247, 244, 240, 235, 231, 225, 220, 213, 207, 200, 193, 185, 178, 170, 162, 154, 146, 138, 129, 121, 113, 106, 98, 91, 83, 76, 70, 63, 57, 51, 46, 41, 36, 32, 28, 24, 20, 17, 15, 12, 10, 8, 6, 5, 4, 3, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; // Use this before the cie_lightness function. static inline uint16_t scale_backlight(uint16_t v) { return v / BACKLIGHT_LEVELS * get_backlight_level(); } void breathing_task(void) { // Only run this ISR at ~120 Hz if (breath_scale_counter++ == BREATHING_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) % (get_breathing_period() * breathing_ISR_frequency); uint8_t index = breathing_counter / interval; // limit index to max step value if (index >= BREATHING_STEPS) { index = BREATHING_STEPS - 1; } if (((breathing_halt == BREATHING_HALT_ON) && (index == BREATHING_STEPS / 2)) || ((breathing_halt == BREATHING_HALT_OFF) && (index == BREATHING_STEPS - 1))) { breathing_interrupt_disable(); } // Set PWM to a brightnessvalue scaled to the configured resolution set_pwm(cie_lightness(rescale_limit_val(scale_backlight((uint32_t)pgm_read_byte(&breathing_table[index]) * ICRx / 255)))); } #endif // BACKLIGHT_BREATHING void backlight_init_ports(void) { // Setup backlight pin as output and output to on state. backlight_pins_init(); // I could write a wall of text here to explain... but TL;DW // Go read the ATmega32u4 datasheet. // And this: http://blog.saikoled.com/post/43165849837/secret-konami-cheat-code-to-high-resolution-pwm-on // TimerX setup, Fast PWM mode count to TOP set in ICRx TCCRxA = _BV(WGM11); // = 0b00000010; // clock select clk/1 TCCRxB = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001; ICRx = BACKLIGHT_RESOLUTION; backlight_init(); #ifdef BACKLIGHT_BREATHING if (is_backlight_breathing()) { breathing_enable(); } #endif }