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@@ -0,0 +1,46 @@
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+
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+#include <avr/io.h>
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+#include "backlight.h"
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+
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+
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+void backlight_init_ports()
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+{
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+ // Setup PB7 as output and output low.
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+ DDRB |= (1<<7);
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+ PORTB &= ~(1<<7);
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+
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+ // Use full 16-bit resolution.
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+ ICR1 = 0xFFFF;
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+
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+ // I could write a wall of text here to explain... but TL;DW
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+ // Go read the ATmega32u4 datasheet.
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+ // And this: http://blog.saikoled.com/post/43165849837/secret-konami-cheat-code-to-high-resolution-pwm-on
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+
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+ // Pin PB7 = OCR1C (Timer 1, Channel C)
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+ // Compare Output Mode = Clear on compare match, Channel C = COM1C1=1 COM1C0=0
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+ // (i.e. start high, go low when counter matches.)
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+ // WGM Mode 14 (Fast PWM) = WGM13=1 WGM12=1 WGM11=1 WGM10=0
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+ // Clock Select = clk/1 (no prescaling) = CS12=0 CS11=0 CS10=1
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+
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+ TCCR1A = _BV(COM1C1) | _BV(WGM11); // = 0b00001010;
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+ TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10); // = 0b00011001;
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+
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+ // Default to zero duty cycle.
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+ OCR1C = 0x0000;
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+}
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+
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+void backlight_set(uint8_t level)
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+{
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+ if ( level == 0 )
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+ {
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+ // Turn off PWM control on PB7, revert to output low.
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+ TCCR1A &= ~(_BV(COM1C1));
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+ }
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+ else
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+ {
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+ // Turn on PWM control of PB7
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+ TCCR1A |= _BV(COM1C1);
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+ OCR1C = level << 12 | 0x0FFF;
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+ }
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+}
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+
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Wilba6582