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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2009 by Bertrik Sikken
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#include <stdbool.h>
#include "config.h"
#include "backlight.h"
#include "backlight-target.h"
#include "system.h"
/*
Backlight driver using the PWM mode of a hardware timer.
The PWM duty cycle depends exponentially on the configured brightness
level. This makes the brightness curve more linear to the human eye.
*/
void _backlight_set_brightness(int brightness)
{
/* pwm = (sqrt(2)**x)-1, where brightness level x = 0..16 */
static const unsigned char logtable[] =
{0, 1, 2, 3, 5, 7, 10, 15, 22, 31, 44, 63, 90, 127, 180, 255};
/* set PWM width */
TCDATA0 = 255 - logtable[brightness];
}
void _backlight_on(void)
{
_backlight_set_brightness(backlight_brightness);
}
void _backlight_off(void)
{
_backlight_set_brightness(MIN_BRIGHTNESS_SETTING);
}
bool _backlight_init(void)
{
/* enable backlight pin as timer output */
PCON0 = ((PCON0 & ~(3 << 4)) | (2 << 4));
/* enable timer clock */
PWRCON &= ~(1 << 4);
/* configure timer */
TCCMD = (1 << 1); /* TC_CLR */
TCCON = (0 << 13) | /* TC_INT1_EN */
(0 << 12) | /* TC_INT0_EN */
(0 << 11) | /* TC_START */
(3 << 8) | /* TC_CS = PCLK / 64 */
(1 << 4); /* TC_MODE_SEL = PWM mode */
TCDATA1 = 255; /* set PWM period */
TCPRE = 30; /* prescaler */
TCCMD = (1 << 0); /* TC_EN */
_backlight_on();
return true;
}
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