49 lines
1.3 KiB
C
49 lines
1.3 KiB
C
|
|
#include <avr/io.h>
|
|
#include "backlight.h"
|
|
|
|
#define CHANNEL OCR1C
|
|
|
|
void backlight_init_ports(uint8_t level)
|
|
{
|
|
|
|
// 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;
|
|
|
|
backlight_init();
|
|
}
|
|
|
|
void backlight_set(uint8_t level)
|
|
{
|
|
if ( level == 0 )
|
|
{
|
|
// Turn off PWM control on PB7, revert to output low.
|
|
TCCR1A &= ~(_BV(COM1C1));
|
|
// CHANNEL = level << OFFSET | 0x0FFF;
|
|
CHANNEL = ((1 << level) - 1);
|
|
}
|
|
else
|
|
{
|
|
// Turn on PWM control of PB7
|
|
TCCR1A |= _BV(COM1C1);
|
|
// CHANNEL = level << OFFSET | 0x0FFF;
|
|
CHANNEL = ((1 << level) - 1);
|
|
}
|
|
} |