660daa51d4
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21532 a1c6a512-1295-4272-9138-f99709370657
113 lines
3.4 KiB
C
113 lines
3.4 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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Interrupt-driven backlight driver using the PWM mode of a hardware timer.
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Backlight brightness is implemented by configuring one of the timers in
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the SoC for PWM mode. In this mode, two interrupts are generated for each
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cycle, one at the start of the cycle and another one sometime between the
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first interrupt and the start of the next cycle. The backlight is switched
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on at the first interrupt and switched off at the second interrupt. This
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way, the position in time of the second interrupt determines the duty cycle
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and thereby the brightness of the backlight.
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The backlight is switched on and off by means of a GPIO pin.
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*/
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void INT_TIMERA(void)
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{
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unsigned int tacon = TACON;
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/* clear interrupts */
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TACON = tacon;
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/* TA_INT1, start of PWM cycle: enable backlight */
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if (tacon & (1 << 17)) {
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PDAT0 |= (1 << 2);
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}
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/* TA_INT0, disable backlight until next cycle */
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if (tacon & (1 << 16)) {
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PDAT0 &= ~(1 << 2);
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}
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}
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void _backlight_set_brightness(int brightness)
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{
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static const unsigned char logtable[] = {0, 1, 2, 3, 5, 7, 10, 15, 22, 31, 44, 63, 90, 127, 180, 255};
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if (brightness == MIN_BRIGHTNESS_SETTING) {
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/* turn backlight fully off and disable interrupt */
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PDAT0 &= ~(1 << 2);
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INTMSK &= ~(1 << 5);
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}
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else if (brightness == MAX_BRIGHTNESS_SETTING) {
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/* turn backlight fully on and disable interrupt */
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PDAT0 |= (1 << 2);
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INTMSK &= ~(1 << 5);
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}
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else {
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/* set PWM width and enable interrupt */
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TADATA0 = logtable[brightness];
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INTMSK |= (1 << 5);
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}
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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 GPIO */
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PCON0 = ((PCON0 & ~(3 << 4)) | (1 << 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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TACMD = (1 << 1); /* TA_CLR */
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TACMD = (1 << 0); /* TA_EN */
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TACON = (1 << 13) | /* TA_INT1_EN */
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(1 << 12) | /* TA_INT0_EN */
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(1 << 11) | /* TA_START */
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(3 << 8) | /* TA_CS = PCLK / 64 */
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(1 << 4); /* TA_MODE_SEL = PWM mode */
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TADATA1 = 255; /* set PWM period */
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TAPRE = 30; /* prescaler */
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_backlight_on();
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return true;
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}
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