1 files changed, 46 insertions, 0 deletions
diff --git a/keyboard/planck/backlight.c b/keyboard/planck/backlight.c
new file mode 100644
index 0000000000..ee7e31ee9c
--- /dev/null
+++ b/keyboard/planck/backlight.c
@@ -0,0 +1,46 @@
+
+#include <avr/io.h>
+#include "backlight.h"
+
+
+void backlight_init_ports()
+{
+    // Setup PB7 as output and output low.
+    DDRB |= (1<<7);
+    PORTB &= ~(1<<7);
+    
+    // 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(COM1C1) | _BV(WGM11); // = 0b00001010;
+    TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
+    
+    // Default to zero duty cycle.
+    OCR1C = 0x0000;
+}
+
+void backlight_set(uint8_t level)
+{
+    if ( level == 0 )
+    {
+        // Turn off PWM control on PB7, revert to output low.
+        TCCR1A &= ~(_BV(COM1C1));
+    }
+    else
+    {
+        // Turn on PWM control of PB7
+        TCCR1A |= _BV(COM1C1);
+        OCR1C = level << 12 | 0x0FFF;
+    }
+}
+