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Diffstat (limited to 'platforms/avr/drivers/backlight_timer.c')
| -rw-r--r-- | platforms/avr/drivers/backlight_timer.c | 267 |
1 files changed, 267 insertions, 0 deletions
diff --git a/platforms/avr/drivers/backlight_timer.c b/platforms/avr/drivers/backlight_timer.c new file mode 100644 index 0000000000..e1f4286557 --- /dev/null +++ b/platforms/avr/drivers/backlight_timer.c @@ -0,0 +1,267 @@ +#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 +} |