backlight breathing overhaul (#2187)

* add breathing to bananasplit

* backlight breathing overhaul

* fix the backlight_tick thing.

* fix for vision_division backlight

* fix a few keymaps and probably break breathing for some weirdly set-up boards.

* remove BL_x keycodes because they made unreasonable assumptions

* some fixes for BL keycodes

* integer cie lightness scaling

* use cie lightness for non-breathing backlight and make breathing able to reach true max brightness

1 files changed, 169 insertions, 237 deletions

diff --git a/quantum/quantum.c b/quantum/quantum.c
index c80975f21..88617412c 100644
--- a/quantum/quantum.c
+++ b/quantum/quantum.c
@@ -23,6 +23,10 @@
 #define TAPPING_TERM 200
 #endif
 
+#ifndef BREATHING_PERIOD
+#define BREATHING_PERIOD 6
+#endif
+
 #include "backlight.h"
 extern backlight_config_t backlight_config;
 
@@ -618,7 +622,17 @@ bool process_record_quantum(keyrecord_t *record) {
       }
 
       send_keyboard_report();
+      return false;
     }
+
+#if defined(BACKLIGHT_ENABLE) && defined(BACKLIGHT_BREATHING)
+    case BL_BRTG: {
+      if (record->event.pressed)
+        breathing_toggle();
+      return false;
+    }
+#endif
+
     default: {
       shift_interrupted[0] = true;
       shift_interrupted[1] = true;
@@ -831,6 +845,7 @@ void matrix_scan_quantum() {
 
 static const uint8_t backlight_pin = BACKLIGHT_PIN;
 
+// depending on the pin, we use a different output compare unit
 #if BACKLIGHT_PIN == B7
 #  define COM1x1 COM1C1
 #  define OCR1x  OCR1C
@@ -841,17 +856,18 @@ static const uint8_t backlight_pin = BACKLIGHT_PIN;
 #  define COM1x1 COM1A1
 #  define OCR1x  OCR1A
 #else
-#  define NO_BACKLIGHT_CLOCK
+#  define NO_HARDWARE_PWM
 #endif
 
 #ifndef BACKLIGHT_ON_STATE
 #define BACKLIGHT_ON_STATE 0
 #endif
 
+#ifdef NO_HARDWARE_PWM // pwm through software
+
 __attribute__ ((weak))
 void backlight_init_ports(void)
 {
-
   // Setup backlight pin as output and output to on state.
   // DDRx |= n
   _SFR_IO8((backlight_pin >> 4) + 1) |= _BV(backlight_pin & 0xF);
@@ -862,83 +878,15 @@ void backlight_init_ports(void)
     // PORTx |= n
     _SFR_IO8((backlight_pin >> 4) + 2) |= _BV(backlight_pin & 0xF);
   #endif
-
-  #ifndef NO_BACKLIGHT_CLOCK
-    // Use full 16-bit resolution.
-    ICR1 = 0xFFFF;
-
-    // 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
-
-    // 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
-
-    TCCR1A = _BV(COM1x1) | _BV(WGM11); // = 0b00001010;
-    TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
-  #endif
-
-  backlight_init();
-  #ifdef BACKLIGHT_BREATHING
-    breathing_defaults();
-  #endif
 }
 
 __attribute__ ((weak))
-void backlight_set(uint8_t level)
-{
-  // Prevent backlight blink on lowest level
-  // #if BACKLIGHT_ON_STATE == 0
-  //   // PORTx &= ~n
-  //   _SFR_IO8((backlight_pin >> 4) + 2) &= ~_BV(backlight_pin & 0xF);
-  // #else
-  //   // PORTx |= n
-  //   _SFR_IO8((backlight_pin >> 4) + 2) |= _BV(backlight_pin & 0xF);
-  // #endif
-
-  if ( level == 0 ) {
-    #ifndef NO_BACKLIGHT_CLOCK
-      // Turn off PWM control on backlight pin, revert to output low.
-      TCCR1A &= ~(_BV(COM1x1));
-      OCR1x = 0x0;
-    #else
-      // #if BACKLIGHT_ON_STATE == 0
-      //   // PORTx |= n
-      //   _SFR_IO8((backlight_pin >> 4) + 2) |= _BV(backlight_pin & 0xF);
-      // #else
-      //   // PORTx &= ~n
-      //   _SFR_IO8((backlight_pin >> 4) + 2) &= ~_BV(backlight_pin & 0xF);
-      // #endif
-    #endif
-  }
-  #ifndef NO_BACKLIGHT_CLOCK
-    else if ( level == BACKLIGHT_LEVELS ) {
-      // Turn on PWM control of backlight pin
-      TCCR1A |= _BV(COM1x1);
-      // Set the brightness
-      OCR1x = 0xFFFF;
-    }
-    else {
-      // Turn on PWM control of backlight pin
-      TCCR1A |= _BV(COM1x1);
-      // Set the brightness
-      OCR1x = 0xFFFF >> ((BACKLIGHT_LEVELS - level) * ((BACKLIGHT_LEVELS + 1) / 2));
-    }
-  #endif
-
-  #ifdef BACKLIGHT_BREATHING
-    breathing_intensity_default();
-  #endif
-}
+void backlight_set(uint8_t level) {}
 
 uint8_t backlight_tick = 0;
 
 void backlight_task(void) {
-  #ifdef NO_BACKLIGHT_CLOCK
-  if ((0xFFFF >> ((BACKLIGHT_LEVELS - backlight_config.level) * ((BACKLIGHT_LEVELS + 1) / 2))) & (1 << backlight_tick)) {
+  if ((0xFFFF >> ((BACKLIGHT_LEVELS - get_backlight_level()) * ((BACKLIGHT_LEVELS + 1) / 2))) & (1 << backlight_tick)) {
     #if BACKLIGHT_ON_STATE == 0
       // PORTx &= ~n
       _SFR_IO8((backlight_pin >> 4) + 2) &= ~_BV(backlight_pin & 0xF);
@@ -955,232 +903,216 @@ void backlight_task(void) {
       _SFR_IO8((backlight_pin >> 4) + 2) &= ~_BV(backlight_pin & 0xF);
     #endif
   }
-  backlight_tick = (backlight_tick + 1) % 16;
-  #endif
+  backlight_tick = backlight_tick + 1 % 16;
 }
 
 #ifdef BACKLIGHT_BREATHING
+#error "Backlight breathing only available with hardware PWM. Please disable."
+#endif
 
-#ifdef NO_BACKLIGHT_CLOCK
-void breathing_defaults(void) {}
-void breathing_intensity_default(void) {}
-#else
+#else // pwm through timer
+
+#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) {
+  OCR1x = val;
+}
+
+__attribute__ ((weak))
+void backlight_set(uint8_t level) {
+  if (level > BACKLIGHT_LEVELS)
+    level = BACKLIGHT_LEVELS;
+
+  if (level == 0) {
+    // Turn off PWM control on backlight pin
+    TCCR1A &= ~(_BV(COM1x1));
+  } else {
+    // Turn on PWM control of backlight pin
+    TCCR1A |= _BV(COM1x1);
+  }
+  // Set the brightness
+  set_pwm(cie_lightness(TIMER_TOP * (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 breath_intensity;
-static uint8_t breath_speed;
-static uint16_t breathing_index;
-static uint8_t breathing_halt;
+static uint8_t breathing_period = BREATHING_PERIOD;
+static uint8_t breathing_halt = BREATHING_NO_HALT;
+static uint16_t breathing_counter = 0;
 
-void breathing_enable(void)
-{
-    if (get_backlight_level() == 0)
-    {
-        breathing_index = 0;
-    }
-    else
-    {
-        // Set breathing_index to be at the midpoint (brightest point)
-        breathing_index = 0x20 << breath_speed;
-    }
+bool is_breathing(void) {
+    return !!(TIMSK1 & _BV(TOIE1));
+}
 
-    breathing_halt = BREATHING_NO_HALT;
+#define breathing_interrupt_enable() do {TIMSK1 |= _BV(TOIE1);} while (0)
+#define breathing_interrupt_disable() do {TIMSK1 &= ~_BV(TOIE1);} while (0)
+#define breathing_min() do {breathing_counter = 0;} while (0)
+#define breathing_max() do {breathing_counter = breathing_period * 244 / 2;} while (0)
 
-    // Enable breathing interrupt
-    TIMSK1 |= _BV(OCIE1A);
+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_index = 0;
-    }
+      breathing_min();
     else
-    {
-        // Set breathing_index to be at the midpoint + 1 (brightest point)
-        breathing_index = 0x21 << breath_speed;
-    }
-
+      breathing_max();
     breathing_halt = BREATHING_HALT_ON;
-
-    // Enable breathing interrupt
-    TIMSK1 |= _BV(OCIE1A);
+    breathing_interrupt_enable();
 }
 
 void breathing_disable(void)
 {
-    // Disable breathing interrupt
-    TIMSK1 &= ~_BV(OCIE1A);
+    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;
-    }
-
-    //backlight_set(get_backlight_level());
+  if (get_backlight_level() == 0)
+    breathing_halt = BREATHING_HALT_OFF;
+  else
+    breathing_halt = BREATHING_HALT_ON;
 }
 
-void breathing_toggle(void)
-{
-    if (!is_breathing())
-    {
-        if (get_backlight_level() == 0)
-        {
-            breathing_index = 0;
-        }
-        else
-        {
-            // Set breathing_index to be at the midpoint + 1 (brightest point)
-            breathing_index = 0x21 << breath_speed;
-        }
-
-        breathing_halt = BREATHING_NO_HALT;
-    }
-
-    // Toggle breathing interrupt
-    TIMSK1 ^= _BV(OCIE1A);
-
-    // Restore backlight level
-    if (!is_breathing())
-    {
-        backlight_set(get_backlight_level());
-    }
+void breathing_toggle(void) {
+  if (is_breathing())
+    breathing_disable();
+  else
+    breathing_enable();
 }
 
-bool is_breathing(void)
+void breathing_period_set(uint8_t value)
 {
-    return (TIMSK1 && _BV(OCIE1A));
+  if (!value)
+    value = 1;
+  breathing_period = value;
 }
 
-void breathing_intensity_default(void)
-{
-    //breath_intensity = (uint8_t)((uint16_t)100 * (uint16_t)get_backlight_level() / (uint16_t)BACKLIGHT_LEVELS);
-    breath_intensity = ((BACKLIGHT_LEVELS - get_backlight_level()) * ((BACKLIGHT_LEVELS + 1) / 2));
+void breathing_period_default(void) {
+  breathing_period_set(BREATHING_PERIOD);
 }
 
-void breathing_intensity_set(uint8_t value)
+void breathing_period_inc(void)
 {
-    breath_intensity = value;
+  breathing_period_set(breathing_period+1);
 }
 
-void breathing_speed_default(void)
+void breathing_period_dec(void)
 {
-    breath_speed = 4;
+  breathing_period_set(breathing_period-1);
 }
 
-void breathing_speed_set(uint8_t value)
-{
-    bool is_breathing_now = is_breathing();
-    uint8_t old_breath_speed = breath_speed;
-
-    if (is_breathing_now)
-    {
-        // Disable breathing interrupt
-        TIMSK1 &= ~_BV(OCIE1A);
-    }
-
-    breath_speed = value;
-
-    if (is_breathing_now)
-    {
-        // Adjust index to account for new speed
-        breathing_index = (( (uint8_t)( (breathing_index) >> old_breath_speed ) ) & 0x3F) << breath_speed;
-
-        // Enable breathing interrupt
-        TIMSK1 |= _BV(OCIE1A);
-    }
-
-}
+/* 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};
 
-void breathing_speed_inc(uint8_t value)
-{
-    if ((uint16_t)(breath_speed - value) > 10 )
-    {
-        breathing_speed_set(0);
-    }
-    else
-    {
-        breathing_speed_set(breath_speed - value);
-    }
+// 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_speed_dec(uint8_t value)
+/* 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(TIMER1_OVF_vect)
 {
-    if ((uint16_t)(breath_speed + value) > 10 )
-    {
-        breathing_speed_set(10);
-    }
-    else
-    {
-        breathing_speed_set(breath_speed + value);
-    }
-}
+  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();
+  }
 
-void breathing_defaults(void)
-{
-    breathing_intensity_default();
-    breathing_speed_default();
-    breathing_halt = BREATHING_NO_HALT;
+  set_pwm(cie_lightness(scale_backlight((uint16_t) pgm_read_byte(&breathing_table[index]) * 0x0101U)));
 }
 
-/* Breathing Sleep LED brighness(PWM On period) table
- * (64[steps] * 4[duration]) / 64[PWM periods/s] = 4 second breath cycle
- *
- * http://www.wolframalpha.com/input/?i=%28sin%28+x%2F64*pi%29**8+*+255%2C+x%3D0+to+63
- * (0..63).each {|x| p ((sin(x/64.0*PI)**8)*255).to_i }
- */
-static const uint8_t breathing_table[64] PROGMEM = {
-  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   1,   2,   4,   6,  10,
- 15,  23,  32,  44,  58,  74,  93, 113, 135, 157, 179, 199, 218, 233, 245, 252,
-255, 252, 245, 233, 218, 199, 179, 157, 135, 113,  93,  74,  58,  44,  32,  23,
- 15,  10,   6,   4,   2,   1,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
-};
+#endif // BACKLIGHT_BREATHING
 
-ISR(TIMER1_COMPA_vect)
+__attribute__ ((weak))
+void backlight_init_ports(void)
 {
-    // OCR1x = (pgm_read_byte(&breathing_table[ ( (uint8_t)( (breathing_index++) >> breath_speed ) ) & 0x3F ] )) * breath_intensity;
-
-
-    uint8_t local_index = ( (uint8_t)( (breathing_index++) >> breath_speed ) ) & 0x3F;
-
-    if (((breathing_halt == BREATHING_HALT_ON) && (local_index == 0x20)) || ((breathing_halt == BREATHING_HALT_OFF) && (local_index == 0x3F)))
-    {
-        // Disable breathing interrupt
-        TIMSK1 &= ~_BV(OCIE1A);
-    }
-
-    OCR1x = (uint16_t)(((uint16_t)pgm_read_byte(&breathing_table[local_index]) * 257)) >> breath_intensity;
+  // Setup backlight pin as output and output to on state.
+  // DDRx |= n
+  _SFR_IO8((backlight_pin >> 4) + 1) |= _BV(backlight_pin & 0xF);
+  #if BACKLIGHT_ON_STATE == 0
+    // PORTx &= ~n
+    _SFR_IO8((backlight_pin >> 4) + 2) &= ~_BV(backlight_pin & 0xF);
+  #else
+    // PORTx |= n
+    _SFR_IO8((backlight_pin >> 4) + 2) |= _BV(backlight_pin & 0xF);
+  #endif
+  // 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
+
+  // 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)."
+  */
+
+  TCCR1A = _BV(COM1x1) | _BV(WGM11); // = 0b00001010;
+  TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
+  // Use full 16-bit resolution. Counter counts to ICR1 before reset to 0.
+  ICR1 = TIMER_TOP;
 
+  backlight_init();
+  #ifdef BACKLIGHT_BREATHING
+    breathing_enable();
+  #endif
 }
 
-#endif // NO_BACKLIGHT_CLOCK
-#endif // breathing
+#endif // NO_HARDWARE_PWM
 
 #else // backlight
 
 __attribute__ ((weak))
-void backlight_init_ports(void)
-{
-
-}
+void backlight_init_ports(void) {}
 
 __attribute__ ((weak))
-void backlight_set(uint8_t level)
-{
-
-}
+void backlight_set(uint8_t level) {}
 
 #endif // backlight