Relocate backlight drivers (#21444)

3 files changed, 814 insertions, 0 deletions

diff --git a/platforms/avr/drivers/backlight_pwm.c b/platforms/avr/drivers/backlight_pwm.c
new file mode 100644
index 0000000000..d234115641
--- /dev/null
+++ b/platforms/avr/drivers/backlight_pwm.c
@@ -0,0 +1,463 @@
+#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
+
+// 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 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 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 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 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 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 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 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
+#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;
+    // 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
+
+#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
+}
diff --git a/platforms/chibios/drivers/backlight_pwm.c b/platforms/chibios/drivers/backlight_pwm.c
new file mode 100644
index 0000000000..01e6f71307
--- /dev/null
+++ b/platforms/chibios/drivers/backlight_pwm.c
@@ -0,0 +1,173 @@
+#include "backlight.h"
+#include "gpio.h"
+#include "wait.h"
+#include <hal.h>
+
+// Maximum duty cycle limit
+#ifndef BACKLIGHT_LIMIT_VAL
+#    define BACKLIGHT_LIMIT_VAL 255
+#endif
+
+#ifndef BACKLIGHT_PAL_MODE
+#    if defined(USE_GPIOV1)
+#        define BACKLIGHT_PAL_MODE PAL_MODE_ALTERNATE_PUSHPULL
+#    else
+// GPIOV2 && GPIOV3
+#        define BACKLIGHT_PAL_MODE 2
+#    endif
+#endif
+
+// GENERIC
+#ifndef BACKLIGHT_PWM_DRIVER
+#    define BACKLIGHT_PWM_DRIVER PWMD4
+#endif
+#ifndef BACKLIGHT_PWM_CHANNEL
+#    define BACKLIGHT_PWM_CHANNEL 3
+#endif
+
+// Support for pins which are on TIM1_CH1N - requires STM32_PWM_USE_ADVANCED
+#ifdef BACKLIGHT_PWM_COMPLEMENTARY_OUTPUT
+#    if BACKLIGHT_ON_STATE == 1
+#        define PWM_OUTPUT_MODE PWM_COMPLEMENTARY_OUTPUT_ACTIVE_LOW;
+#    else
+#        define PWM_OUTPUT_MODE PWM_COMPLEMENTARY_OUTPUT_ACTIVE_HIGH;
+#    endif
+#else
+#    if BACKLIGHT_ON_STATE == 1
+#        define PWM_OUTPUT_MODE PWM_OUTPUT_ACTIVE_HIGH;
+#    else
+#        define PWM_OUTPUT_MODE PWM_OUTPUT_ACTIVE_LOW;
+#    endif
+#endif
+
+#ifndef BACKLIGHT_PWM_COUNTER_FREQUENCY
+#    define BACKLIGHT_PWM_COUNTER_FREQUENCY 0xFFFF
+#endif
+
+#ifndef BACKLIGHT_PWM_PERIOD
+#    define BACKLIGHT_PWM_PERIOD 256
+#endif
+
+static PWMConfig pwmCFG = {
+    .frequency = BACKLIGHT_PWM_COUNTER_FREQUENCY, /* PWM clock frequency  */
+    .period    = BACKLIGHT_PWM_PERIOD,            /* PWM period in counter ticks. e.g. clock frequency is 10KHz, period is 256 ticks then t_period is 25.6ms */
+};
+
+#ifdef BACKLIGHT_BREATHING
+static virtual_timer_t breathing_vt;
+#endif
+
+// 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;
+        }
+    }
+}
+
+static uint32_t rescale_limit_val(uint32_t val) {
+    // rescale the supplied backlight value to be in terms of the value limit
+    return (val * (BACKLIGHT_LIMIT_VAL + 1)) / 256;
+}
+
+void backlight_init_ports(void) {
+#ifdef USE_GPIOV1
+    palSetPadMode(PAL_PORT(BACKLIGHT_PIN), PAL_PAD(BACKLIGHT_PIN), BACKLIGHT_PAL_MODE);
+#else
+    palSetPadMode(PAL_PORT(BACKLIGHT_PIN), PAL_PAD(BACKLIGHT_PIN), PAL_MODE_ALTERNATE(BACKLIGHT_PAL_MODE));
+#endif
+
+    pwmCFG.channels[BACKLIGHT_PWM_CHANNEL - 1].mode = PWM_OUTPUT_MODE;
+    pwmStart(&BACKLIGHT_PWM_DRIVER, &pwmCFG);
+
+    backlight_set(get_backlight_level());
+
+#ifdef BACKLIGHT_BREATHING
+    chVTObjectInit(&breathing_vt);
+    if (is_backlight_breathing()) {
+        breathing_enable();
+    }
+#endif
+}
+
+void backlight_set(uint8_t level) {
+    if (level > BACKLIGHT_LEVELS) {
+        level = BACKLIGHT_LEVELS;
+    }
+
+    if (level == 0) {
+        // Turn backlight off
+        pwmDisableChannel(&BACKLIGHT_PWM_DRIVER, BACKLIGHT_PWM_CHANNEL - 1);
+    } else {
+        // Turn backlight on
+        uint32_t duty = (uint32_t)(cie_lightness(rescale_limit_val(0xFFFF * (uint32_t)level / BACKLIGHT_LEVELS)));
+        pwmEnableChannel(&BACKLIGHT_PWM_DRIVER, BACKLIGHT_PWM_CHANNEL - 1, PWM_FRACTION_TO_WIDTH(&BACKLIGHT_PWM_DRIVER, 0xFFFF, duty));
+    }
+}
+
+void backlight_task(void) {}
+
+#ifdef BACKLIGHT_BREATHING
+
+#    define BREATHING_STEPS 128
+
+/* 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};
+
+static void breathing_callback(virtual_timer_t *vtp, void *p);
+
+bool is_breathing(void) {
+    return chVTIsArmed(&breathing_vt);
+}
+
+void breathing_enable(void) {
+    /* Update frequency is 256Hz -> 3906us intervals */
+    chVTSetContinuous(&breathing_vt, TIME_US2I(3906), breathing_callback, NULL);
+}
+
+void breathing_disable(void) {
+    chVTReset(&breathing_vt);
+
+    // Restore backlight level
+    backlight_set(get_backlight_level());
+}
+
+// Use this before the cie_lightness function.
+static inline uint16_t scale_backlight(uint16_t v) {
+    return v / BACKLIGHT_LEVELS * get_backlight_level();
+}
+
+static void breathing_callback(virtual_timer_t *vtp, void *p) {
+    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.
+    static uint16_t breathing_counter = 0;
+    breathing_counter                 = (breathing_counter + 1) % (breathing_period * 256);
+    uint8_t  index                    = breathing_counter / interval % BREATHING_STEPS;
+    uint32_t duty                     = cie_lightness(rescale_limit_val(scale_backlight(breathing_table[index] * 256)));
+
+    chSysLockFromISR();
+    pwmEnableChannelI(&BACKLIGHT_PWM_DRIVER, BACKLIGHT_PWM_CHANNEL - 1, PWM_FRACTION_TO_WIDTH(&BACKLIGHT_PWM_DRIVER, 0xFFFF, duty));
+    chSysUnlockFromISR();
+}
+
+// TODO: integrate generic pulse solution
+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
diff --git a/platforms/chibios/drivers/backlight_timer.c b/platforms/chibios/drivers/backlight_timer.c
new file mode 100644
index 0000000000..0fabee93b1
--- /dev/null
+++ b/platforms/chibios/drivers/backlight_timer.c
@@ -0,0 +1,178 @@
+#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