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

2 files changed, 178 insertions, 0 deletions

diff --git a/firmware/target/arm/imx233/button-lradc-imx233.c b/firmware/target/arm/imx233/button-lradc-imx233.c
new file mode 100644
index 0000000000..66d42a47dc
--- /dev/null
+++ b/firmware/target/arm/imx233/button-lradc-imx233.c
@@ -0,0 +1,122 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   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.
+ *
+ ****************************************************************************/
+#include "button-lradc-imx233.h"
+#include "stdlib.h"
+#include "lradc-imx233.h"
+
+#ifndef IMX233_BUTTON_LRADC_CHANNEL
+#error You must define IMX233_BUTTON_LRADC_CHANNEL to use button-lradc
+#endif
+
+/* physical channel */
+#define CHAN    IMX233_BUTTON_LRADC_CHANNEL
+/* number of irq per second */
+#ifdef IMX233_BUTTON_LRADC_RATE
+# define RATE    IMX233_BUTTON_LRADC_RATE
+#else
+# define RATE    HZ
+#endif
+/* number of samples per irq */
+#ifdef IMX233_BUTTON_LRADC_SAMPLES
+# define SAMPLES    IMX233_BUTTON_LRADC_SAMPLES
+#else
+# define SAMPLES    10
+#endif
+/* delay's delay */
+#define DELAY   (LRADC_DELAY_FREQ / RATE / SAMPLES)
+
+static int button_delay;
+static int button_chan;
+static int button_val[2];
+static int button_idx;
+static int button_mask;
+static int table_size;
+
+static int button_find(int val)
+{
+    // shortcuts
+    struct imx233_button_lradc_mapping_t *table = imx233_button_lradc_mapping;
+    /* FIXME use a dichotomy */
+    int i = 0;
+    while(i < table_size && val >= table[i].adc_val)
+        i++;
+    // extreme cases
+    int btn = 0;
+    // if i=n then choose i-1 and otherwise choose best between i-1 and i
+    if(i == 0)
+        btn = table[0].btn;
+    else if(i == table_size)
+        btn = table[i - 1].btn;
+    // choose best between i-1 and i (note that table[i-1]<=val<=table[i]) */
+    else if(val - table[i - 1].adc_val < table[i].adc_val - val)
+        btn = table[i - 1].btn;
+    else
+        btn = table[i].btn;
+    return btn;
+}
+
+int button_value;
+
+static void button_lradc_irq(int chan)
+{
+    (void) chan;
+    /* read value, kick channel */
+    button_val[button_idx] = imx233_lradc_read_channel(button_chan) / SAMPLES;
+    imx233_lradc_clear_channel(button_chan);
+    imx233_lradc_setup_channel(button_chan, true, true, SAMPLES - 1, LRADC_SRC(CHAN));
+    imx233_lradc_setup_delay(button_delay, 1 << button_chan, 0, SAMPLES - 1, DELAY);
+    imx233_lradc_kick_delay(button_delay);
+    button_value = button_val[button_idx];
+    /* compute mask, compare to previous one */
+    button_val[button_idx] = button_find(button_val[button_idx]);
+    button_idx = 1 - button_idx;
+    if(button_val[0] == button_val[1])
+        button_mask = button_val[0];
+}
+
+void imx233_button_lradc_init(void)
+{
+    button_chan = imx233_lradc_acquire_channel(LRADC_SRC(CHAN), TIMEOUT_NOBLOCK);
+    if(button_chan < 0)
+        panicf("Cannot get channel for button-lradc");
+    button_delay = imx233_lradc_acquire_delay(TIMEOUT_NOBLOCK);
+    if(button_delay < 0)
+        panicf("Cannot get delay for button-lradc");
+    imx233_lradc_setup_channel(button_chan, true, true, SAMPLES - 1, LRADC_SRC(CHAN));
+    imx233_lradc_setup_delay(button_delay, 1 << button_chan, 0, SAMPLES - 1, DELAY);
+    imx233_lradc_enable_channel_irq(button_chan, true);
+    imx233_lradc_set_channel_irq_callback(button_chan, button_lradc_irq);
+    imx233_lradc_kick_delay(button_delay);
+
+    table_size = 0;
+    while(imx233_button_lradc_mapping[table_size].btn != IMX233_BUTTON_LRADC_END)
+        table_size++;
+}
+
+bool imx233_button_lradc_hold(void)
+{
+    return button_mask == IMX233_BUTTON_LRADC_HOLD;
+}
+
+int imx233_button_lradc_read(void)
+{
+    return button_mask == IMX233_BUTTON_LRADC_HOLD ? 0 : button_mask;
+}
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__ */