From b80b6b369c5ecb5c7232edf1e8cebe8c12078d6e Mon Sep 17 00:00:00 2001
From: Wilba6582 <Jason.S.Wiliams@gmail.com>
Date: Tue, 17 Mar 2015 00:51:36 +1100
Subject: [PATCH] Added backlight.h, backlight.c

---
 keyboard/planck/backlight.c | 46 +++++++++++++++++++++++++++++++++++++
 keyboard/planck/backlight.h |  2 ++
 2 files changed, 48 insertions(+)
 create mode 100644 keyboard/planck/backlight.c
 create mode 100644 keyboard/planck/backlight.h

diff --git a/keyboard/planck/backlight.c b/keyboard/planck/backlight.c
new file mode 100644
index 000000000..d12dcf238
--- /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
index 000000000..0fe1f4a72
--- /dev/null
+++ b/keyboard/planck/backlight.h
@@ -0,0 +1,2 @@
+
+void backlight_init_ports(void);
-- 
2.39.2