Add software backlight fading for E100/H300/X5/D2, by Thomas Martitz and others - see FS#6800 for credits.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19221 a1c6a512-1295-4272-9138-f99709370657

18 files changed, 304 insertions, 39 deletions

diff --git a/apps/features.txt b/apps/features.txt
index 118465a..0a01eb9 100644
--- a/apps/features.txt
+++ b/apps/features.txt
@@ -20,7 +20,7 @@ albumart
 backlight_brightness
 #endif
 
-#if defined(HAVE_BACKLIGHT_PWM_FADING)
+#if defined(HAVE_BACKLIGHT_PWM_FADING) || defined(USE_BACKLIGHT_SW_FADING)
 backlight_fade
 #endif
 
diff --git a/apps/menus/display_menu.c b/apps/menus/display_menu.c
index 016255b..744a9e9 100644
--- a/apps/menus/display_menu.c
+++ b/apps/menus/display_menu.c
@@ -91,7 +91,8 @@ MENUITEM_SETTING(backlight_on_button_hold,
                 &global_settings.backlight_on_button_hold, NULL);
 #endif
 MENUITEM_SETTING(caption_backlight, &global_settings.caption_backlight, NULL);
-#if defined(HAVE_BACKLIGHT_PWM_FADING) && !defined(SIMULATOR)
+#if (defined(HAVE_BACKLIGHT_PWM_FADING) && !defined(SIMULATOR)) || \
+        defined(USE_BACKLIGHT_SW_FADING)
 MENUITEM_SETTING(backlight_fade_in, &global_settings.backlight_fade_in, NULL);
 MENUITEM_SETTING(backlight_fade_out, &global_settings.backlight_fade_out, NULL);
 #endif
@@ -130,9 +131,10 @@ MAKE_MENU(lcd_settings,ID2P(LANG_LCD_MENU),
             ,&backlight_on_button_hold
 # endif
             ,&caption_backlight
-# if defined(HAVE_BACKLIGHT_PWM_FADING) && !defined(SIMULATOR)
+#if (defined(HAVE_BACKLIGHT_PWM_FADING) && !defined(SIMULATOR)) || \
+        defined(USE_BACKLIGHT_SW_FADING)
             ,&backlight_fade_in, &backlight_fade_out
-# endif
+#endif
             ,&bl_filter_first_keypress
 # ifdef HAVE_LCD_SLEEP_SETTING
             ,&lcd_sleep_after_backlight_off
diff --git a/apps/settings.c b/apps/settings.c
index bdfaba2..2cab26a 100644
--- a/apps/settings.c
+++ b/apps/settings.c
@@ -768,7 +768,8 @@ void settings_apply(bool read_disk)
 #if CONFIG_CHARGING
     backlight_set_timeout_plugged(global_settings.backlight_timeout_plugged);
 #endif
-#if defined(HAVE_BACKLIGHT_PWM_FADING) && !defined(SIMULATOR)
+#if (defined(HAVE_BACKLIGHT_PWM_FADING) && !defined(SIMULATOR)) \
+        || defined(USE_BACKLIGHT_SW_FADING)
     backlight_set_fade_in(global_settings.backlight_fade_in);
     backlight_set_fade_out(global_settings.backlight_fade_out);
 #endif
diff --git a/apps/settings.h b/apps/settings.h
index c5658aa..56b7d3e 100644
--- a/apps/settings.h
+++ b/apps/settings.h
@@ -421,10 +421,14 @@ struct user_settings
     int backlight_timeout_plugged;
 #endif
 
-#ifdef HAVE_BACKLIGHT_PWM_FADING
+#if defined(HAVE_BACKLIGHT_PWM_FADING)
     int backlight_fade_in;  /* backlight fade in timing: 0..3 */
     int backlight_fade_out; /* backlight fade in timing: 0..7 */
+#elif defined(USE_BACKLIGHT_SW_FADING)
+    bool backlight_fade_in;
+    bool backlight_fade_out;
 #endif
+
 #ifdef HAVE_BACKLIGHT_BRIGHTNESS 
     int brightness;
 #endif
diff --git a/apps/settings_list.c b/apps/settings_list.c
index 6a7fcc3..f4519f5 100644
--- a/apps/settings_list.c
+++ b/apps/settings_list.c
@@ -679,6 +679,11 @@ const struct settings_list settings[] = {
                   UNIT_MS, formatter_unit_0_is_off, getlang_unit_0_is_off,
                   backlight_set_fade_out, 10,
                   0,100,200,300,500,1000,2000,3000,5000,10000),
+#elif defined(USE_BACKLIGHT_SW_FADING)
+    OFFON_SETTING(0, backlight_fade_in, LANG_BACKLIGHT_FADE_IN,
+                    true, "backlight fade in", backlight_set_fade_in),
+    OFFON_SETTING(0, backlight_fade_out, LANG_BACKLIGHT_FADE_OUT,
+                    true, "backlight fade out", backlight_set_fade_out),
 #endif
     INT_SETTING(F_PADTITLE, scroll_speed, LANG_SCROLL_SPEED, 9,"scroll speed",
                 UNIT_INT, 0, 15, 1, NULL, NULL, lcd_scroll_speed),
diff --git a/firmware/SOURCES b/firmware/SOURCES
index 4e40d11..47dcfe5 100644
--- a/firmware/SOURCES
+++ b/firmware/SOURCES
@@ -96,6 +96,10 @@ drivers/lcd-remote-2bit-vi.c
 #endif /* LCD_REMOTE_DEPTH */
 #endif /* HAVE_REMOTE_LCD */
 
+#ifdef USE_BACKLIGHT_SW_FADING
+backlight-thread-fading.c
+#endif /* USE_BACKLIGHT_SW_FADING */
+
 /* Misc. */
 drivers/led.c
 drivers/button.c
diff --git a/firmware/backlight-thread-fading.c b/firmware/backlight-thread-fading.c
new file mode 100644
index 0000000..30778a9
--- /dev/null
+++ b/firmware/backlight-thread-fading.c
@@ -0,0 +1,87 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2008 by Thomas Martitz
+ * Copyright (C) 2008 by Martin Ritter
+ *
+ * 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 "backlight-target.h"
+#include "config.h"
+#include "system.h"
+#include "backlight.h"
+#include "backlight-thread-fading.h"
+
+/* To adapt a target do:
+ * - make sure _backlight_on doesn't set the brightness to something other than
+ *  the previous value (lowest brightness in most cases)
+ * - #define USE_BACKLIGHT_SW_FADING in config-<target>.h
+ */
+
+/* can be MIN_BRIGHTNESS_SETTING-1 */
+static int current_brightness = DEFAULT_BRIGHTNESS_SETTING;
+
+void _backlight_fade_update_state(int brightness)
+{
+        current_brightness = brightness;
+}
+
+/* returns true if fade is finished */
+static bool _backlight_fade_up(void)
+{
+    if (LIKELY(current_brightness < backlight_brightness))
+    {
+        _backlight_set_brightness(++current_brightness);
+    }
+    return(current_brightness >= backlight_brightness);
+}
+
+/* returns true if fade is finished */
+static bool _backlight_fade_down(void)
+{
+    if (LIKELY(current_brightness > MIN_BRIGHTNESS_SETTING))
+    {
+        _backlight_set_brightness(--current_brightness);
+        return false;
+    }
+    else
+    {
+        /* decrement once more, since backlight is off */
+        current_brightness--;
+        _backlight_off();
+        return true;
+    }
+}
+
+bool _backlight_fade_step(int direction)
+{
+    bool done;
+    switch(direction)
+    {
+        case FADING_UP:
+            done = _backlight_fade_up();
+        break;
+        case FADING_DOWN:
+            done = _backlight_fade_down();
+        break;
+        default:
+            done = true;
+        break;
+    }
+    return(done);
+}
diff --git a/firmware/backlight.c b/firmware/backlight.c
index b8becfa..fe9c215 100644
--- a/firmware/backlight.c
+++ b/firmware/backlight.c
@@ -8,6 +8,8 @@
  * $Id$
  *
  * Copyright (C) 2002 by Linus Nielsen Feltzing
+ * Additional work by Martin Ritter (2007) and Thomas Martitz (2008)
+ *                  for backlight thread fading
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -46,6 +48,9 @@
 #define BACKLIGHT_FULL_INIT
 #endif
 
+#ifdef USE_BACKLIGHT_SW_FADING
+#include "backlight-thread-fading.h"
+#endif
 #ifdef SIMULATOR
 /* TODO: find a better way to do it but we need a kernel thread somewhere to
    handle this */
@@ -134,6 +139,10 @@ static int backlight_timeout_plugged = 5*HZ;
 static int backlight_on_button_hold = 0;
 #endif
 
+#ifdef HAVE_BACKLIGHT_BRIGHTNESS
+int backlight_brightness = DEFAULT_BRIGHTNESS_SETTING;
+#endif
+
 #ifdef HAVE_BUTTON_LIGHT
 static int buttonlight_timer;
 int _buttonlight_timeout = 5*HZ;
@@ -221,6 +230,12 @@ void backlight_lcd_sleep_countdown(bool start)
 }
 #endif /* HAVE_LCD_SLEEP */
 
+#ifdef USE_BACKLIGHT_SW_FADING
+static int backlight_fading_type = (FADING_UP|FADING_DOWN);
+static int backlight_fading_state = NOT_FADING;
+#endif
+
+
 #if defined(HAVE_BACKLIGHT_PWM_FADING) && !defined(SIMULATOR)
 /* backlight fading */
 #define BL_PWM_INTERVAL 5  /* Cycle interval in ms */
@@ -397,6 +412,66 @@ void backlight_set_fade_out(int value)
 }
 #endif /* defined(HAVE_BACKLIGHT_PWM_FADING) && !defined(SIMULATOR) */
 
+#ifdef USE_BACKLIGHT_SW_FADING
+
+void backlight_set_fade_out(bool value)
+{
+    if(value) /* on */
+        backlight_fading_type |= FADING_DOWN;
+    else
+        backlight_fading_type &= FADING_UP;
+}
+
+void backlight_set_fade_in(bool value)
+{
+    if(value) /* on */
+        backlight_fading_type |= FADING_UP;
+    else
+        backlight_fading_type &= FADING_DOWN;
+}
+
+static void backlight_set_up_fade_up(void)
+{
+    if (backlight_fading_type & FADING_UP)
+    {
+        if (backlight_fading_state == NOT_FADING)
+        {
+            /* make sure the backlight is at lowest level */
+            _backlight_on();
+        }
+        backlight_fading_state = FADING_UP;
+    }
+    else
+    {
+        backlight_fading_state = NOT_FADING;
+        _backlight_fade_update_state(backlight_brightness);
+        _backlight_on();
+        _backlight_set_brightness(backlight_brightness);
+    }
+}
+
+static void backlight_set_up_fade_down(void)
+{
+    if (backlight_fading_type & FADING_DOWN)
+    {
+        backlight_fading_state = FADING_DOWN;
+    }
+    else
+    {
+        backlight_fading_state = NOT_FADING;
+        _backlight_fade_update_state(MIN_BRIGHTNESS_SETTING-1);
+        _backlight_off();
+    /* h300/x5/d2 go to the last known brightness level at backight_on(),which
+     * should be the lowest level to keep fading up glitch free
+     * sansa e200/c200 make the backlight on only by setting the brightness,
+     * so this step would be noticeable */
+#if !defined(SANSA_E200) && !defined(SANSA_C200)
+        _backlight_set_brightness(MIN_BRIGHTNESS_SETTING);
+#endif
+    }
+}
+#endif /* USE_BACKLIGHT_SW_FADING */
+
 /* Update state of backlight according to timeout setting */
 static void backlight_update_state(void)
 {
@@ -424,15 +499,25 @@ static void backlight_update_state(void)
             backlight_timeout = backlight_timeout_normal;
 
     /* Backlight == OFF in the setting? */
-    if (backlight_timeout < 0)
+    if (UNLIKELY(backlight_timeout < 0))
     {
         backlight_timer = 0; /* Disable the timeout */
+#ifdef USE_BACKLIGHT_SW_FADING
+        backlight_set_up_fade_down();
+        /* necessary step to issue fading down when the setting is selected */
+        queue_post(&backlight_queue, SYS_TIMEOUT, 0);
+#else
         _backlight_off();
+#endif
     }
     else
     {
         backlight_timer = backlight_timeout;
+#if defined(USE_BACKLIGHT_SW_FADING)
+        backlight_set_up_fade_up();
+#else
         _backlight_on();
+#endif
     }
 }
 
@@ -478,7 +563,15 @@ void backlight_thread(void)
 
     while(1)
     {
-        queue_wait(&backlight_queue, &ev);
+#if defined(USE_BACKLIGHT_SW_FADING)
+        if (backlight_fading_state)
+            queue_wait_w_tmo(&backlight_queue, &ev, FADE_DELAY);
+        else
+#endif
+            queue_wait(&backlight_queue, &ev);
+/*
+#endif
+*/
         switch(ev.id)
         {   /* These events must always be processed */
 #ifdef _BACKLIGHT_FADE_BOOST
@@ -558,9 +651,12 @@ void backlight_thread(void)
 
             case BACKLIGHT_OFF:
                 backlight_timer = 0; /* Disable the timeout */
+#ifndef USE_BACKLIGHT_SW_FADING
                 _backlight_off();
+#else
+                backlight_set_up_fade_down();
+#endif /* USE_BACKLIGHT_SW_FADING */
                 break;
-
 #ifdef HAVE_LCD_SLEEP
             case LCD_SLEEP:
                 lcd_sleep();
@@ -589,6 +685,12 @@ void backlight_thread(void)
                 remote_backlight_update_state();
 #endif
                 break;
+#if defined(USE_BACKLIGHT_SW_FADING)
+            case SYS_TIMEOUT:
+                if ((_backlight_fade_step(backlight_fading_state)))
+                    backlight_fading_state = NOT_FADING;
+                break;
+#endif /* USE_BACKLIGHT_SW_FADING */
         }
     } /* end while */
 }
@@ -597,8 +699,7 @@ static void backlight_tick(void)
 {
     if(backlight_timer)
     {
-        backlight_timer--;
-        if(backlight_timer == 0)
+        if(--backlight_timer == 0)
         {
             backlight_off();
         }
@@ -606,20 +707,17 @@ static void backlight_tick(void)
 #ifdef HAVE_LCD_SLEEP
     else if(lcd_sleep_timer)
     {
-        lcd_sleep_timer--;
-        if(lcd_sleep_timer == 0)
+        if(--lcd_sleep_timer == 0)
         {
             /* Queue on bl thread or freeze! */
             queue_post(&backlight_queue, LCD_SLEEP, 0);
         }
     }
 #endif /* HAVE_LCD_SLEEP */
-
 #ifdef HAVE_REMOTE_LCD
     if(remote_backlight_timer)
     {
-        remote_backlight_timer--;
-        if(remote_backlight_timer == 0)
+        if(--remote_backlight_timer == 0)
         {
             remote_backlight_off();
         }
@@ -628,8 +726,7 @@ static void backlight_tick(void)
 #ifdef HAVE_BUTTON_LIGHT
     if (buttonlight_timer)
     {
-        buttonlight_timer--;
-        if (buttonlight_timer == 0)
+        if (--buttonlight_timer == 0)
         {
             buttonlight_off();
         }
@@ -832,6 +929,11 @@ void backlight_set_brightness(int val)
         val = MAX_BRIGHTNESS_SETTING;
 
     _backlight_set_brightness(val);
+    backlight_brightness = val;
+#ifdef USE_BACKLIGHT_SW_FADING
+    /* receive backlight brightness */
+    _backlight_fade_update_state(val);
+#endif
 }
 #endif /* HAVE_BACKLIGHT_BRIGHTNESS */
 
diff --git a/firmware/export/backlight-thread-fading.h b/firmware/export/backlight-thread-fading.h
new file mode 100644
index 0000000..ca9c195
--- /dev/null
+++ b/firmware/export/backlight-thread-fading.h
@@ -0,0 +1,46 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id:$
+ *
+ * Copyright (C) 2007 by Will Robertson
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+#ifndef BACKLIGHT_THREAD_FADING_H
+#define BACKLIGHT_THREAD_FADING_H
+
+#include "config.h"
+
+#ifdef USE_BACKLIGHT_SW_FADING
+
+/* delay supposed to be MAX_BRIGHTNESS_SETTING*2 rounded to the next multiple
+ * of 5, however not more than 40 */
+#define _FADE_DELAY (((MAX_BRIGHTNESS_SETTING*2+4)/5)*5)
+#define FADE_DELAY (HZ/(MIN(_FADE_DELAY, 40)))
+
+void _backlight_fade_update_state(int brightness);
+bool _backlight_fade_step(int direction);
+
+/* enum used for both, fading state and fading type selected through the settings */
+
+enum {
+    NOT_FADING = 0,
+    FADING_UP,
+    FADING_DOWN,
+};
+#endif /* USE_BACKLIGHT_SW_FADING */
+
+#endif /* _BACKLIGHT_THREAD_FADING_ */
diff --git a/firmware/export/backlight.h b/firmware/export/backlight.h
index e098065..a177fe7 100644
--- a/firmware/export/backlight.h
+++ b/firmware/export/backlight.h
@@ -34,10 +34,16 @@ void backlight_close(void);
 
 int  backlight_get_current_timeout(void);
 
-#ifdef HAVE_BACKLIGHT_PWM_FADING
+#if defined(HAVE_BACKLIGHT_PWM_FADING)
 void backlight_set_fade_in(int value);
 void backlight_set_fade_out(int value);
 #endif
+#ifdef USE_BACKLIGHT_SW_FADING
+void backlight_set_fade_in(bool value);
+void backlight_set_fade_out(bool value);
+#endif
+
+extern int backlight_brightness;
 
 void backlight_set_timeout_plugged(int value);
 
diff --git a/firmware/export/config-c200.h b/firmware/export/config-c200.h
index a96b9c7..8e26585 100644
--- a/firmware/export/config-c200.h
+++ b/firmware/export/config-c200.h
@@ -132,6 +132,10 @@
 /** Non-simulator section **/
 #ifndef SIMULATOR
 
+/* define this if the backlight thread is used for fade, not for sim, needs
+ * HAVE_BACKLIGHT_BRIGHTNESS */
+#define USE_BACKLIGHT_SW_FADING
+
 /* Define this if you have a PortalPlayer PP5024 */
 #define CONFIG_CPU PP5022
 
diff --git a/firmware/export/config-cowond2.h b/firmware/export/config-cowond2.h
index fd696aa..b723201 100644
--- a/firmware/export/config-cowond2.h
+++ b/firmware/export/config-cowond2.h
@@ -122,6 +122,10 @@
 
 #ifndef SIMULATOR
 
+/* define this if the backlight thread is used for fade, not for sim, needs
+ * HAVE_BACKLIGHT_BRIGHTNESS */
+#define USE_BACKLIGHT_SW_FADING
+
 /* Define this if you have a TCC7801 */
 #define CONFIG_CPU TCC7801
 
diff --git a/firmware/export/config-e200.h b/firmware/export/config-e200.h
index 075f490..d9bebef 100644
--- a/firmware/export/config-e200.h
+++ b/firmware/export/config-e200.h
@@ -129,6 +129,10 @@
 /** Non-simulator section **/
 #ifndef SIMULATOR
 
+/* define this if the backlight thread is used for fade, not for sim, needs
+ * HAVE_BACKLIGHT_BRIGHTNESS */
+#define USE_BACKLIGHT_SW_FADING
+
 /* Define this if you have a PortalPlayer PP5024 */
 #define CONFIG_CPU PP5024
 
diff --git a/firmware/export/config-h300.h b/firmware/export/config-h300.h
index f45b694..2af426f 100644
--- a/firmware/export/config-h300.h
+++ b/firmware/export/config-h300.h
@@ -114,6 +114,11 @@
 
 #ifndef SIMULATOR
 
+/* define this if the backlight thread is used for fade, not for sim, needs
+ * HAVE_BACKLIGHT_BRIGHTNESS */
+#define USE_BACKLIGHT_SW_FADING
+
+
 /* Define this if your LCD can be enabled/disabled */
 #define HAVE_LCD_ENABLE
 
diff --git a/firmware/export/config-iaudiox5.h b/firmware/export/config-iaudiox5.h
index cdae55a..089d219 100644
--- a/firmware/export/config-iaudiox5.h
+++ b/firmware/export/config-iaudiox5.h
@@ -124,6 +124,9 @@
 
 #ifndef SIMULATOR
 
+/* define this if the backlight thread is used for fade, not for sim */
+#define USE_BACKLIGHT_SW_FADING
+
 /* Define this if your LCD can set contrast */
 #define HAVE_LCD_CONTRAST
 
diff --git a/firmware/target/arm/sandisk/backlight-c200_e200.c b/firmware/target/arm/sandisk/backlight-c200_e200.c
index b3984ca..67e0cdd 100644
--- a/firmware/target/arm/sandisk/backlight-c200_e200.c
+++ b/firmware/target/arm/sandisk/backlight-c200_e200.c
@@ -26,16 +26,9 @@
 #include "ascodec.h"
 #include "as3514.h"
 
-static unsigned short backlight_brightness = DEFAULT_BRIGHTNESS_SETTING;
-
 void _backlight_set_brightness(int brightness)
 {
-    backlight_brightness = brightness;
-
-    if (brightness > 0)
-        _backlight_on();
-    else
-        _backlight_off();
+    ascodec_write(AS3514_DCDC15, brightness);
 }
 
 void _backlight_on(void)
@@ -46,7 +39,10 @@ void _backlight_on(void)
 #ifdef HAVE_LCD_ENABLE
     lcd_enable(true); /* power on lcd + visible display */
 #endif
-    ascodec_write(AS3514_DCDC15, backlight_brightness);
+#ifndef USE_BACKLIGHT_SW_FADING
+    /* that part ain't useful when fading */
+    _backlight_set_brightness(backlight_brightness);
+#endif
 }
 
 void _backlight_off(void)
diff --git a/firmware/target/arm/sandisk/backlight-target.h b/firmware/target/arm/sandisk/backlight-target.h
index 21fad6d..1f5e475 100644
--- a/firmware/target/arm/sandisk/backlight-target.h
+++ b/firmware/target/arm/sandisk/backlight-target.h
@@ -25,7 +25,6 @@
 void _backlight_on(void);
 void _backlight_off(void);
 void _backlight_set_brightness(int brightness);
-int  __backlight_is_on(void);
 
 void _buttonlight_on(void);
 void _buttonlight_off(void);
diff --git a/firmware/target/arm/tcc780x/cowond2/backlight-cowond2.c b/firmware/target/arm/tcc780x/cowond2/backlight-cowond2.c
index 6d286ae..39a9abf 100644
--- a/firmware/target/arm/tcc780x/cowond2/backlight-cowond2.c
+++ b/firmware/target/arm/tcc780x/cowond2/backlight-cowond2.c
@@ -24,27 +24,20 @@
 #include "pcf50606.h"
 #include "tcc780x.h"
 
-static unsigned short backlight_brightness = DEFAULT_BRIGHTNESS_SETTING;
-
 int _backlight_init(void)
 {
     _backlight_set_brightness(DEFAULT_BRIGHTNESS_SETTING);
+    /* set backlight on by default, since the screen is unreadable without it */
+    _backlight_on();
     return true;
 }
 
 void _backlight_set_brightness(int brightness)
 {
-    backlight_brightness = brightness;
-
     int level = disable_irq_save();
-    pcf50606_write(PCF5060X_PWMC1, 0xe1 | (14-backlight_brightness)<<1);
+    pcf50606_write(PCF5060X_PWMC1, 0xe1 | (MAX_BRIGHTNESS_SETTING-brightness)<<1);
     pcf50606_write(PCF5060X_GPOC1, 0x3);
     restore_irq(level);
-    
-    if (brightness > 0)
-        _backlight_on();
-    else
-        _backlight_off();
 }
 
 void _backlight_on(void)