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opensteno_qmk/quantum/backlight/backlight_avr.c
Karl Shea 84b8cdc1a4
Fix bit loss in cie_lightness() when doing division to resolve #15331 (#15344) 
* Fix bit loss in cie_lightness() when doing division.

* Use the right types

* Format

Co-authored-by: zvecr <git@zvecr.com>
2021-11-29 15:07:36 +00:00

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#include "quantum.h"
#include "backlight.h"
#include "backlight_driver_common.h"
#include "debug.h"
// Maximum duty cycle limit
#ifndef BACKLIGHT_LIMIT_VAL
# define BACKLIGHT_LIMIT_VAL 255
#endif
// This logic is a bit complex, we support 3 setups:
//
// 1. Hardware PWM when backlight is wired to a PWM pin.
// Depending on this pin, we use a different output compare unit.
// 2. Software PWM with hardware timers, but the used timer
// depends on the Audio setup (Audio wins over Backlight).
// 3. Full software PWM, driven by the matrix scan, if both timers are used by Audio.
#if (defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB647__) || defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__) || defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__)) && (BACKLIGHT_PIN == B5 || BACKLIGHT_PIN == B6 || BACKLIGHT_PIN == B7)
# define HARDWARE_PWM
# define ICRx ICR1
# define TCCRxA TCCR1A
# define TCCRxB TCCR1B
# define TIMERx_OVF_vect TIMER1_OVF_vect
# define TIMSKx TIMSK1
# define TOIEx TOIE1
# if BACKLIGHT_PIN == B5
# define COMxx0 COM1A0
# define COMxx1 COM1A1
# define OCRxx OCR1A
# elif BACKLIGHT_PIN == B6
# define COMxx0 COM1B0
# define COMxx1 COM1B1
# define OCRxx OCR1B
# elif BACKLIGHT_PIN == B7
# define COMxx0 COM1C0
# define COMxx1 COM1C1
# define OCRxx OCR1C
# endif
#elif (defined(__AVR_AT90USB646__) || defined(__AVR_AT90USB647__) || defined(__AVR_AT90USB1286__) || defined(__AVR_AT90USB1287__) || defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__)) && (BACKLIGHT_PIN == C4 || BACKLIGHT_PIN == C5 || BACKLIGHT_PIN == C6)
# define HARDWARE_PWM
# define ICRx ICR3
# define TCCRxA TCCR3A
# define TCCRxB TCCR3B
# define TIMERx_OVF_vect TIMER3_OVF_vect
# define TIMSKx TIMSK3
# define TOIEx TOIE3
# if BACKLIGHT_PIN == C4
# if (defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__))
# error This MCU has no C4 pin!
# else
# define COMxx0 COM3C0
# define COMxx1 COM3C1
# define OCRxx OCR3C
# endif
# elif BACKLIGHT_PIN == C5
# if (defined(__AVR_ATmega16U4__) || defined(__AVR_ATmega32U4__))
# error This MCU has no C5 pin!
# else
# define COMxx0 COM3B0
# define COMxx1 COM3B1
# define OCRxx OCR3B
# endif
# elif BACKLIGHT_PIN == C6
# define COMxx0 COM3A0
# define COMxx1 COM3A1
# define OCRxx OCR3A
# endif
#elif (defined(__AVR_AT90USB162__) || defined(__AVR_ATmega16U2__) || defined(__AVR_ATmega32U2__)) && (BACKLIGHT_PIN == B7 || BACKLIGHT_PIN == C5 || BACKLIGHT_PIN == C6)
# define HARDWARE_PWM
# define ICRx ICR1
# define TCCRxA TCCR1A
# define TCCRxB TCCR1B
# define TIMERx_OVF_vect TIMER1_OVF_vect
# define TIMSKx TIMSK1
# define TOIEx TOIE1
# if BACKLIGHT_PIN == B7
# define COMxx0 COM1C0
# define COMxx1 COM1C1
# define OCRxx OCR1C
# elif BACKLIGHT_PIN == C5
# define COMxx0 COM1B0
# define COMxx1 COM1B1
# define OCRxx OCR1B
# elif BACKLIGHT_PIN == C6
# define COMxx0 COM1A0
# define COMxx1 COM1A1
# define OCRxx OCR1A
# endif
#elif defined(__AVR_ATmega32A__) && (BACKLIGHT_PIN == D4 || BACKLIGHT_PIN == D5)
# define HARDWARE_PWM
# define ICRx ICR1
# define TCCRxA TCCR1A
# define TCCRxB TCCR1B
# define TIMERx_OVF_vect TIMER1_OVF_vect
# define TIMSKx TIMSK
# define TOIEx TOIE1
# if BACKLIGHT_PIN == D4
# define COMxx0 COM1B0
# define COMxx1 COM1B1
# define OCRxx OCR1B
# elif BACKLIGHT_PIN == D5
# define COMxx0 COM1A0
# define COMxx1 COM1A1
# define OCRxx OCR1A
# endif
#elif (defined(__AVR_ATmega328P__) || defined(__AVR_ATmega328__)) && (BACKLIGHT_PIN == B1 || BACKLIGHT_PIN == B2)
# define HARDWARE_PWM
# define ICRx ICR1
# define TCCRxA TCCR1A
# define TCCRxB TCCR1B
# define TIMERx_OVF_vect TIMER1_OVF_vect
# define TIMSKx TIMSK1
# define TOIEx TOIE1
# if BACKLIGHT_PIN == B1
# define COMxx0 COM1A0
# define COMxx1 COM1A1
# define OCRxx OCR1A
# elif BACKLIGHT_PIN == B2
# define COMxx0 COM1B0
# define COMxx1 COM1B1
# define OCRxx OCR1B
# endif
#elif (AUDIO_PIN != B5) && (AUDIO_PIN != B6) && (AUDIO_PIN != B7) && (AUDIO_PIN_ALT != B5) && (AUDIO_PIN_ALT != B6) && (AUDIO_PIN_ALT != B7)
// Timer 1 is not in use by Audio feature, Backlight can use it
# pragma message "Using hardware timer 1 with software PWM"
# define HARDWARE_PWM
# define BACKLIGHT_PWM_TIMER
# 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 (AUDIO_PIN != C4) && (AUDIO_PIN != C5) && (AUDIO_PIN != C6)
# pragma message "Using hardware timer 3 with software PWM"
// Timer 3 is not in use by Audio feature, Backlight can use it
# define HARDWARE_PWM
# define BACKLIGHT_PWM_TIMER
# 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
#elif defined(BACKLIGHT_CUSTOM_DRIVER)
error("Please set 'BACKLIGHT_DRIVER = custom' within rules.mk")
#else
error("Please set 'BACKLIGHT_DRIVER = software' within rules.mk")
#endif
#ifndef BACKLIGHT_PWM_TIMER // pwm through software
static inline void enable_pwm(void) {
# if BACKLIGHT_ON_STATE == 1
TCCRxA |= _BV(COMxx1);
# else
TCCRxA |= _BV(COMxx1) | _BV(COMxx0);
# endif
}
static inline void disable_pwm(void) {
# if BACKLIGHT_ON_STATE == 1
TCCRxA &= ~(_BV(COMxx1));
# else
TCCRxA &= ~(_BV(COMxx1) | _BV(COMxx0));
# endif
}
#endif
#ifdef BACKLIGHT_PWM_TIMER
// 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_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/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();
}
}
#endif
#define TIMER_TOP 0xFFFFU
// 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) {
#ifdef BACKLIGHT_PWM_TIMER
if (OCRxx) {
TIMSKx &= ~(_BV(OCIExA));
TIMSKx &= ~(_BV(TOIEx));
}
#else
// Turn off PWM control on backlight pin
disable_pwm();
#endif
backlight_pins_off();
} else {
#ifdef BACKLIGHT_PWM_TIMER
if (!OCRxx) {
TIMSKx |= _BV(OCIExA);
TIMSKx |= _BV(TOIEx);
}
#else
// Turn on PWM control of backlight pin
enable_pwm();
#endif
}
// 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 uint16_t breathing_freq_scale_factor = 2;
# ifdef BACKLIGHT_PWM_TIMER
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)
# else
bool is_breathing(void) { return !!(TIMSKx & _BV(TOIEx)); }
# define breathing_interrupt_enable() \
do { \
TIMSKx |= _BV(TOIEx); \
} while (0)
# define breathing_interrupt_disable() \
do { \
TIMSKx &= ~_BV(TOIEx); \
} while (0)
# endif
# 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(); }
# ifdef BACKLIGHT_PWM_TIMER
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
{
// 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) % (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 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
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
#ifdef BACKLIGHT_PWM_TIMER
// 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;
#else // hardware PWM
// Pin PB7 = OCR1C (Timer 1, Channel C)
// Compare Output Mode = Clear on compare match, Channel C = COM1C1=1 COM1C0=0
// (i.e. start high, go low when counter matches.)
// WGM Mode 14 (Fast PWM) = WGM13=1 WGM12=1 WGM11=1 WGM10=0
// Clock Select = clk/1 (no prescaling) = CS12=0 CS11=0 CS10=1
/*
14.8.3:
"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)."
*/
TCCRxA = _BV(COMxx1) | _BV(WGM11); // = 0b00001010;
TCCRxB = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
#endif
#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
if (is_backlight_breathing()) {
breathing_enable();
}
#endif
}
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