Added backlight.h, backlight.c

diff --git a/keyboard/planck/backlight.c b/keyboard/planck/backlight.c
new file mode 100644 (file)
index 0000000..d12dcf2
--- /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;
+       }
+}
+

diff --git a/keyboard/planck/backlight.h b/keyboard/planck/backlight.h
new file mode 100644 (file)
index 0000000..0fe1f4a
--- /dev/null
+++ b/keyboard/planck/backlight.h
@@ -0,0 +1,2 @@
+
+void backlight_init_ports(void);