adds backlight levels to the satan keyboard (#431)

* enable 4 levels

* remove breathing stuff

* update channels, comments, hex

keyboard/satan/Makefile

@@ -68,10 +68,6 @@ AUDIO_ENABLE ?= no
 UNICODE_ENABLE ?= no 		# Unicode
 BLUETOOTH_ENABLE ?= no # Enable Bluetooth with the Adafruit EZ-Key HID
 
-#ifdef BACKLIGHT_ENABLE
-    SRC := backlight.c $(SRC)
-#endif
-
 ifndef QUANTUM_DIR
 	include ../../Makefile
 endif

keyboard/satan/backlight.c

@@ -1,24 +0,0 @@
-
-#include <avr/io.h>
-#include "backlight.h"
-#include "print.h"
-
-void init_backlight_pin(void) {
-    print("init_backlight_pin()\n");
-    // Set our LED pins as output
-    DDRB |= (1<<6);
-
-    // Set our LED pins low
-    PORTB &= ~(1<<6);
-}
-
-void backlight_set(uint8_t level) {
-    if ( level == 0 ) {
-        // Turn off light
-        PORTB |= (1<<6);
-    } else {
-        // Turn on light
-        PORTB &= ~(1<<6);
-    }
-}
-

keyboard/satan/config.h

@@ -59,7 +59,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 /* Backlight configuration
  */
-#define BACKLIGHT_LEVELS 1
+#define BACKLIGHT_LEVELS 4
 
 /* Underlight configuration
  */

keyboard/satan/satan.c

@@ -14,6 +14,64 @@ void matrix_scan_user(void) {
 	// leave these blank
 };
 
+
+#ifdef BACKLIGHT_ENABLE
+
+void backlight_init_ports()
+{
+
+    // Setup PB6 as output and output low.
+    DDRB |= (1<<6);
+    PORTB &= ~(1<<6);
+
+    // 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 PB6 = OCR1B (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(COM1B1) | _BV(WGM11); // = 0b00001010;
+    TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
+
+    backlight_init();
+}
+
+void backlight_set(uint8_t level)
+{
+    // Prevent backlight blink on lowest level
+    PORTB &= ~(_BV(PORTB6));
+
+    if ( level == 0 )
+    {
+        // Turn off PWM control on PB6, revert to output low.
+        TCCR1A &= ~(_BV(COM1B1));
+        OCR1B = 0x0;
+    }
+    else if ( level == BACKLIGHT_LEVELS )
+    {
+        // Turn on PWM control of PB6
+        TCCR1A |= _BV(COM1B1);
+        // Set the brightness
+        OCR1B = 0xFFFF;
+    }
+    else
+    {
+        // Turn on PWM control of PB6
+        TCCR1A |= _BV(COM1B1);
+        // Set the brightness
+        OCR1B = 0xFFFF >> ((BACKLIGHT_LEVELS - level) * ((BACKLIGHT_LEVELS + 1) / 2));
+    }
+}
+
+#endif
+
 void matrix_init_kb(void) {
 	// put your keyboard start-up code here
 	// runs once when the firmware starts up
@@ -23,7 +81,7 @@ void matrix_init_kb(void) {
 	led_init_ports();
 
     #ifdef BACKLIGHT_ENABLE
-        init_backlight_pin();
+        backlight_init_ports();
     #endif
 };