From eb7cf73dcbc7fff1a17aee93656e30c4a9f3f9f3 Mon Sep 17 00:00:00 2001
From: Bertrik Sikken <bertrik@sikken.nl>
Date: Sun, 30 Oct 2011 20:15:08 +0000
Subject: Sansa clip zip: use a state machine for scanning buttons to avoid
 busy-waits

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30871 a1c6a512-1295-4272-9138-f99709370657
---
 .../arm/as3525/sansa-clipzip/button-clipzip.c      | 96 +++++++++++++---------
 1 file changed, 55 insertions(+), 41 deletions(-)

(limited to 'firmware/target')

diff --git a/firmware/target/arm/as3525/sansa-clipzip/button-clipzip.c b/firmware/target/arm/as3525/sansa-clipzip/button-clipzip.c
index e960b49b77..40b20cdce3 100644
--- a/firmware/target/arm/as3525/sansa-clipzip/button-clipzip.c
+++ b/firmware/target/arm/as3525/sansa-clipzip/button-clipzip.c
@@ -27,6 +27,59 @@
 #include "kernel.h"
 #include "system-target.h"
 
+static int keyscan(void)
+{
+    static int buttons = 0;
+    static int row = 1;
+
+    switch (row) {
+    
+    case 1:
+        /* read row 1 */
+        buttons &= ~(BUTTON_RIGHT | BUTTON_SELECT | BUTTON_UP);
+        if (GPIOC_PIN(3)) {
+            buttons |= BUTTON_RIGHT;
+        }
+        if (GPIOC_PIN(4)) {
+            buttons |= BUTTON_SELECT;
+        }
+        if (GPIOC_PIN(5)) {
+            buttons |= BUTTON_UP;
+        }
+        
+        /* prepare row 2 */
+        GPIOC_PIN(1) = 0;
+        GPIOC_PIN(2) = (1 << 2);
+        row = 2;
+        break;
+        
+    case 2:
+        /* read row 2 */
+        buttons &= ~(BUTTON_HOME | BUTTON_DOWN | BUTTON_LEFT);
+        if (GPIOC_PIN(3)) {
+            buttons |= BUTTON_HOME;
+        }
+        if (GPIOC_PIN(4)) {
+            buttons |= BUTTON_DOWN;
+        }
+        if (GPIOC_PIN(5)) {
+            buttons |= BUTTON_LEFT;
+        }
+    
+        /* prepare row 1 */
+        GPIOC_PIN(1) = (1 << 1);
+        GPIOC_PIN(2) = 0;
+        row = 1;
+        break;
+
+    default:
+        row = 1;
+        break;
+    }
+    
+    return buttons;
+}
+
 void button_init_device(void)
 {
     /* GPIO A6, A7 and D6 are direct button inputs */
@@ -39,15 +92,6 @@ void button_init_device(void)
     GPIOC_DIR &= ~((1 << 3) | (1 << 4) | (1 << 5));
 }
 
-/*  TODO:
-    Instead of using udelay to wait for buttons to settle, we could use a
-    simple state machine to alternate between key matrix rows (like we do on
-    the clip) and this way avoid burning cycles in the udelay.
-    
-    TODO:
-    Figure out the real mappings from GPIOs to buttons.
-    The current mapping is just an educated guess.
-*/
 int button_read_device(void)
 {
     int buttons = 0;
@@ -64,39 +108,9 @@ int button_read_device(void)
     if (GPIOA_PIN(7)) {
         buttons |= BUTTON_VOL_UP;
     }
-
-    /* key matrix buttons, first row */
-    GPIOC_PIN(1) = (1 << 1);
-    GPIOC_PIN(2) = 0;
-    udelay(500);
-    
-    if (GPIOC_PIN(3)) {
-        buttons |= BUTTON_RIGHT;
-    }
-    if (GPIOC_PIN(4)) {
-        buttons |= BUTTON_SELECT;
-    }
-    if (GPIOC_PIN(5)) {
-        buttons |= BUTTON_UP;
-    }
-    
-    /* key matrix buttons, second row */
-    GPIOC_PIN(1) = 0;
-    GPIOC_PIN(2) = (1 << 2);
-    udelay(500);
-    
-    if (GPIOC_PIN(3)) {
-        buttons |= BUTTON_HOME;
-    }
-    if (GPIOC_PIN(4)) {
-        buttons |= BUTTON_DOWN;
-    }
-    if (GPIOC_PIN(5)) {
-        buttons |= BUTTON_LEFT;
-    }
     
-    /* deselect scan rows */
-    GPIOC_PIN(2) = 0;
+    /* keyscan buttons */
+    buttons |= keyscan();
 
     return buttons;
 }
-- 
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