imx233: add generic lradc based button driver

This driver does debouncing and best lradc usage and only requires
a sorted table of values to work, this factoring code as much as
possible.

Change-Id: I84b46f4b08094634e1c5deb5ca9ba20763389e66

1 files changed, 56 insertions, 0 deletions

diff --git a/firmware/target/arm/imx233/button-lradc-imx233.h b/firmware/target/arm/imx233/button-lradc-imx233.h
new file mode 100644
index 0000000000..d3e6ad8326
--- /dev/null
+++ b/firmware/target/arm/imx233/button-lradc-imx233.h
@@ -0,0 +1,56 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2013 by Amaury Pouly
+ *
+ * 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 __button_lradc_imx233__
+#define __button_lradc_imx233__
+
+#include "button.h"
+#include "button-target.h"
+
+/** This driver implements button sensing with lradc. It does debouncing
+ * and can handle hold sensing too. It can be tweaked using the following defines
+ * and variables:
+ * - imx233_button_lradc_mapping: target-defined table of adc values and mapping
+ * - IMX233_BUTTON_LRADC_CHANNEL: lradc channel to use
+ */
+
+/* special value for btn to handle HOLD */
+#define IMX233_BUTTON_LRADC_END     -1
+#define IMX233_BUTTON_LRADC_HOLD    -2
+
+struct imx233_button_lradc_mapping_t
+{
+    int adc_val;
+    int btn;
+};
+
+/* target-defined
+ * NOTE for proper operation, the table should contain entries for all states, including:
+ * - one with adc_val set to default value when no button is pressed
+ * - one with adc_val set to value when hold is selected (if hold is sensed using adc)
+ * - a dummy entry with btn set to IMX233_BUTTON_LRADC_END as the last entry
+ * The table must be sorted by increasing values of adc_val */
+extern struct imx233_button_lradc_mapping_t imx233_button_lradc_mapping[];
+
+void imx233_button_lradc_init(void);
+int imx233_button_lradc_read(void);
+bool imx233_button_lradc_hold(void);
+
+#endif /* __button_lradc_imx233__ */