From 2fb73842a9b51e554a3a14feb0b4c0814c82ebec Mon Sep 17 00:00:00 2001
From: Bertrik Sikken <bertrik@sikken.nl>
Date: Wed, 29 Jul 2009 20:42:02 +0000
Subject: Start of a Rockbox port to the Samsung YP-S3.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@22085 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/target/arm/s5l8700/yps3/backlight-yps3.c | 78 +++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 firmware/target/arm/s5l8700/yps3/backlight-yps3.c

(limited to 'firmware/target/arm/s5l8700/yps3/backlight-yps3.c')

diff --git a/firmware/target/arm/s5l8700/yps3/backlight-yps3.c b/firmware/target/arm/s5l8700/yps3/backlight-yps3.c
new file mode 100644
index 0000000000..0a9cf3cc9a
--- /dev/null
+++ b/firmware/target/arm/s5l8700/yps3/backlight-yps3.c
@@ -0,0 +1,78 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   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 */
+    TADATA0 = 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 << 0)) | (2 << 0));
+
+    /* enable timer clock */
+    PWRCON &= ~(1 << 4);
+
+    /* configure timer */
+    TACMD = (1 << 1);   /* TC_CLR */
+    TACON = (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 */
+    TADATA1 = 255;      /* set PWM period */
+    TAPRE = 20;         /* prescaler */
+    TACMD = (1 << 0);   /* TC_EN */
+   
+    _backlight_on();
+
+    return true;
+}
+
-- 
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