backlight: split AVR PWM and timer drivers (#21540)

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
+}