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#include "backlight.h"
#include "backlight_driver_common.h"
#include "wait.h"
#ifndef BACKLIGHT_GPT_DRIVER
# define BACKLIGHT_GPT_DRIVER GPTD15
#endif
// Platform specific implementations
static void backlight_timer_configure(bool enable);
static void backlight_timer_set_duty(uint16_t duty);
static uint16_t backlight_timer_get_duty(void);
// 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;
}
}
void backlight_init_ports(void) {
backlight_pins_init();
backlight_set(get_backlight_level());
#ifdef BACKLIGHT_BREATHING
if (is_backlight_breathing()) {
breathing_enable();
}
#endif
}
void backlight_set(uint8_t level) {
if (level > BACKLIGHT_LEVELS) level = BACKLIGHT_LEVELS;
backlight_pins_off();
backlight_timer_set_duty(cie_lightness(0xFFFFU / BACKLIGHT_LEVELS * level));
backlight_timer_configure(level != 0);
}
static void backlight_timer_top(void) {
#ifdef BACKLIGHT_BREATHING
if (is_breathing()) {
breathing_task();
}
#endif
if (backlight_timer_get_duty() > 256) {
backlight_pins_on();
}
}
static void backlight_timer_cmp(void) {
backlight_pins_off();
}
void backlight_task(void) {}
#ifdef BACKLIGHT_BREATHING
# define BREATHING_STEPS 128
static bool breathing = false;
static uint16_t breathing_counter = 0;
/* 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] = {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) {
uint8_t breathing_period = get_breathing_period();
uint16_t interval = (uint16_t)breathing_period * 256 / BREATHING_STEPS;
// resetting after one period to prevent ugly reset at overflow.
breathing_counter = (breathing_counter + 1) % (breathing_period * 256);
uint8_t index = breathing_counter / interval % BREATHING_STEPS;
// printf("index:%u\n", index);
backlight_timer_set_duty(cie_lightness(scale_backlight((uint16_t)breathing_table[index] * 256)));
}
bool is_breathing(void) {
return breathing;
}
void breathing_enable(void) {
breathing_counter = 0;
breathing = true;
}
void breathing_disable(void) {
breathing = false;
}
void breathing_pulse(void) {
backlight_set(is_backlight_enabled() ? 0 : BACKLIGHT_LEVELS);
wait_ms(10);
backlight_set(is_backlight_enabled() ? get_backlight_level() : 0);
}
#endif
#ifdef PROTOCOL_CHIBIOS
// On Platforms where timers fire every tick and have no capture/top events
// - fake event in the normal timer callback
uint16_t s_duty = 0;
static void timerCallback(void) {
/* Software PWM
* timer:1111 1111 1111 1111
* \______/| \_______/____ count(0-255)
* \ \______________ unused(1)
* \__________________ index of step table(0-127)
*/
// this works for cca 65536 irqs/sec
static union {
uint16_t raw;
struct {
uint16_t count : 8;
uint8_t dummy : 1;
uint8_t index : 7;
} pwm;
} timer = {.raw = 0};
timer.raw++;
if (timer.pwm.count == 0) {
// LED on
backlight_timer_top();
} else if (timer.pwm.count == (s_duty / 256)) {
// LED off
backlight_timer_cmp();
}
}
static void backlight_timer_set_duty(uint16_t duty) {
s_duty = duty;
}
static uint16_t backlight_timer_get_duty(void) {
return s_duty;
}
// ChibiOS - Map GPT timer onto Software PWM
static void gptTimerCallback(GPTDriver *gptp) {
(void)gptp;
timerCallback();
}
static void backlight_timer_configure(bool enable) {
static const GPTConfig gptcfg = {1000000, gptTimerCallback, 0, 0};
static bool s_init = false;
if (!s_init) {
gptStart(&BACKLIGHT_GPT_DRIVER, &gptcfg);
s_init = true;
}
if (enable) {
gptStartContinuous(&BACKLIGHT_GPT_DRIVER, gptcfg.frequency / 0xFFFF);
} else {
gptStopTimer(&BACKLIGHT_GPT_DRIVER);
}
}
#endif
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