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qmk_firmware/quantum/backlight/backlight_avr.c
Joel Challis 4531cc874e
Initial migration of software PWM backlight (#6709) 
* Initial migration of software PWM backlight

* First pass at backlight driver docs

* Correct driver name in docs

* Run backlight_task when using BACKLIGHT_PINS

* Resolve backlight docs TODOs
2019-11-02 21:20:03 +00:00

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#include "quantum.h"
#include "backlight.h"
#include "debug.h"
#if defined(BACKLIGHT_ENABLE) && (defined(BACKLIGHT_PIN) || defined(BACKLIGHT_PINS))
// 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 COMxx1 COM1A1
# define OCRxx OCR1A
# elif BACKLIGHT_PIN == B6
# define COMxx1 COM1B1
# define OCRxx OCR1B
# elif BACKLIGHT_PIN == B7
# 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 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 COMxx1 COM3B1
# define OCRxx OCR3B
# endif
# elif BACKLIGHT_PIN == C6
# define COMxx1 COM3A1
# define OCRxx OCR3A
# endif
# elif (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 COMxx1 COM1C1
# define OCRxx OCR1C
# elif BACKLIGHT_PIN == C5
# define COMxx1 COM1B1
# define OCRxx OCR1B
# elif BACKLIGHT_PIN == C6
# 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 COMxx1 COM1B1
# define OCRxx OCR1B
# elif BACKLIGHT_PIN == D5
# define COMxx1 COM1A1
# define OCRxx OCR1A
# endif
# elif defined(__AVR_ATmega328P__) && (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 COMxx1 COM1A1
# define OCRxx OCR1A
# elif BACKLIGHT_PIN == B2
# define COMxx1 COM1B1
# define OCRxx OCR1B
# endif
# else
# if !defined(BACKLIGHT_CUSTOM_DRIVER)
# if !defined(B5_AUDIO) && !defined(B6_AUDIO) && !defined(B7_AUDIO)
// 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 !defined(C6_AUDIO) && !defined(C5_AUDIO) && !defined(C4_AUDIO)
# 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
# else
# pragma message "Audio in use - using pure software PWM"
# define NO_HARDWARE_PWM
# endif
# else
# pragma message "Custom driver defined - using pure software PWM"
# define NO_HARDWARE_PWM
# endif
# endif
# ifndef BACKLIGHT_ON_STATE
# define BACKLIGHT_ON_STATE 0
# endif
void backlight_on(pin_t backlight_pin) {
# if BACKLIGHT_ON_STATE == 0
writePinLow(backlight_pin);
# else
writePinHigh(backlight_pin);
# endif
}
void backlight_off(pin_t backlight_pin) {
# if BACKLIGHT_ON_STATE == 0
writePinHigh(backlight_pin);
# else
writePinLow(backlight_pin);
# endif
}
# if defined(NO_HARDWARE_PWM) || defined(BACKLIGHT_PWM_TIMER) // pwm through software
// we support multiple backlight pins
# ifndef BACKLIGHT_LED_COUNT
# define BACKLIGHT_LED_COUNT 1
# endif
# if BACKLIGHT_LED_COUNT == 1
# define BACKLIGHT_PIN_INIT \
{ BACKLIGHT_PIN }
# else
# define BACKLIGHT_PIN_INIT BACKLIGHT_PINS
# endif
# define FOR_EACH_LED(x) \
for (uint8_t i = 0; i < BACKLIGHT_LED_COUNT; i++) { \
pin_t backlight_pin = backlight_pins[i]; \
{ x } \
}
static const pin_t backlight_pins[BACKLIGHT_LED_COUNT] = BACKLIGHT_PIN_INIT;
# else // full hardware PWM
// we support only one backlight pin
static const pin_t backlight_pin = BACKLIGHT_PIN;
# define FOR_EACH_LED(x) x
# endif
# ifdef NO_HARDWARE_PWM
__attribute__((weak)) void backlight_init_ports(void) {
// Setup backlight pin as output and output to on state.
FOR_EACH_LED(setPinOutput(backlight_pin); backlight_on(backlight_pin);)
# ifdef BACKLIGHT_BREATHING
if (is_backlight_breathing()) {
breathing_enable();
}
# endif
}
__attribute__((weak)) void backlight_set(uint8_t level) {}
uint8_t backlight_tick = 0;
# ifndef BACKLIGHT_CUSTOM_DRIVER
void backlight_task(void) {
if ((0xFFFF >> ((BACKLIGHT_LEVELS - get_backlight_level()) * ((BACKLIGHT_LEVELS + 1) / 2))) & (1 << backlight_tick)) {
FOR_EACH_LED(backlight_on(backlight_pin);)
} else {
FOR_EACH_LED(backlight_off(backlight_pin);)
}
backlight_tick = (backlight_tick + 1) % 16;
}
# endif
# ifdef BACKLIGHT_BREATHING
# ifndef BACKLIGHT_CUSTOM_DRIVER
# error "Backlight breathing only available with hardware PWM. Please disable."
# endif
# endif
# else // hardware pwm through timer
# 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.
// Triggered when the counter reaches the OCRx value
ISR(TIMERx_COMPA_vect) { FOR_EACH_LED(backlight_off(backlight_pin);) }
// Triggered when the counter reaches the TOP value
// this one triggers at F_CPU/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 > 256) {
FOR_EACH_LED(backlight_on(backlight_pin);)
}
}
# 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 <= 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;
}
}
// range for val is [0..TIMER_TOP]. PWM pin is high while the timer count is below val.
static inline void set_pwm(uint16_t val) { OCRxx = val; }
# ifndef BACKLIGHT_CUSTOM_DRIVER
__attribute__((weak)) 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));
FOR_EACH_LED(backlight_off(backlight_pin);)
}
# else
// Turn off PWM control on backlight pin
TCCRxA &= ~(_BV(COMxx1));
# endif
} else {
# ifdef BACKLIGHT_PWM_TIMER
if (!OCRxx) {
TIMSKx |= _BV(OCIExA);
TIMSKx |= _BV(TOIEx);
}
# else
// Turn on PWM control of backlight pin
TCCRxA |= _BV(COMxx1);
# endif
}
// Set the brightness
set_pwm(cie_lightness(TIMER_TOP * (uint32_t)level / BACKLIGHT_LEVELS));
}
void backlight_task(void) {}
# endif // BACKLIGHT_CUSTOM_DRIVER
# 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_period = BREATHING_PERIOD;
static uint8_t breathing_halt = BREATHING_NO_HALT;
static uint16_t breathing_counter = 0;
# 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 = breathing_period * 244 / 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;
}
void breathing_toggle(void) {
if (is_breathing())
breathing_disable();
else
breathing_enable();
}
void breathing_period_set(uint8_t value) {
if (!value) value = 1;
breathing_period = value;
}
void breathing_period_default(void) { breathing_period_set(BREATHING_PERIOD); }
void breathing_period_inc(void) { breathing_period_set(breathing_period + 1); }
void breathing_period_dec(void) { breathing_period_set(breathing_period - 1); }
/* 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.
*/
ISR(TIMERx_OVF_vect)
# endif
{
uint16_t interval = (uint16_t)breathing_period * 244 / 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;
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(scale_backlight((uint16_t)pgm_read_byte(&breathing_table[index]) * 0x0101U)));
}
# endif // BACKLIGHT_BREATHING
__attribute__((weak)) void backlight_init_ports(void) {
// Setup backlight pin as output and output to on state.
FOR_EACH_LED(setPinOutput(backlight_pin); backlight_on(backlight_pin);)
// 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
// Use full 16-bit resolution. Counter counts to ICR1 before reset to 0.
ICRx = TIMER_TOP;
backlight_init();
# ifdef BACKLIGHT_BREATHING
if (is_backlight_breathing()) {
breathing_enable();
}
# endif
}
# endif // hardware backlight
#else // no backlight
__attribute__((weak)) void backlight_init_ports(void) {}
__attribute__((weak)) void backlight_set(uint8_t level) {}
#endif // backlight
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