306753b1ed
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21772 a1c6a512-1295-4272-9138-f99709370657
78 lines
2.3 KiB
C
78 lines
2.3 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2009 by Bertrik Sikken
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#include <stdbool.h>
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#include "config.h"
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#include "backlight.h"
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#include "backlight-target.h"
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#include "system.h"
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/*
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Backlight driver using the PWM mode of a hardware timer.
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The PWM duty cycle depends exponentially on the configured brightness
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level. This makes the brightness curve more linear to the human eye.
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*/
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void _backlight_set_brightness(int brightness)
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{
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/* pwm = (sqrt(2)**x)-1, where brightness level x = 0..16 */
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static const unsigned char logtable[] =
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{0, 1, 2, 3, 5, 7, 10, 15, 22, 31, 44, 63, 90, 127, 180, 255};
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/* set PWM width */
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TCDATA0 = 255 - logtable[brightness];
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}
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void _backlight_on(void)
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{
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_backlight_set_brightness(backlight_brightness);
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}
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void _backlight_off(void)
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{
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_backlight_set_brightness(MIN_BRIGHTNESS_SETTING);
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}
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bool _backlight_init(void)
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{
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/* enable backlight pin as timer output */
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PCON0 = ((PCON0 & ~(3 << 4)) | (2 << 4));
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/* enable timer clock */
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PWRCON &= ~(1 << 4);
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/* configure timer */
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TCCMD = (1 << 1); /* TC_CLR */
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TCCON = (0 << 13) | /* TC_INT1_EN */
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(0 << 12) | /* TC_INT0_EN */
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(0 << 11) | /* TC_START */
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(3 << 8) | /* TC_CS = PCLK / 64 */
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(1 << 4); /* TC_MODE_SEL = PWM mode */
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TCDATA1 = 255; /* set PWM period */
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TCPRE = 30; /* prescaler */
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TCCMD = (1 << 0); /* TC_EN */
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_backlight_on();
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return true;
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}
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