zenxfi3: rewrite mpr121 driver

The new driver uses an asynchronous architecture for touch status reading.

Change-Id: Ic75a8b91bc47ee16c3af873afde178cd70186376

4 files changed, 433 insertions, 76 deletions

diff --git a/firmware/target/arm/imx233/creative-zenxfi3/backlight-zenxfi3.c b/firmware/target/arm/imx233/creative-zenxfi3/backlight-zenxfi3.c
index 2b77a4d..e3badde 100644
--- a/firmware/target/arm/imx233/creative-zenxfi3/backlight-zenxfi3.c
+++ b/firmware/target/arm/imx233/creative-zenxfi3/backlight-zenxfi3.c
@@ -25,7 +25,7 @@
 #include "backlight.h"
 #include "backlight-target.h"
 #include "pwm-imx233.h"
-#include "mpr121.h"
+#include "mpr121-zenxfi3.h"
 
 void backlight_hw_brightness(int brightness)
 {
diff --git a/firmware/target/arm/imx233/creative-zenxfi3/button-zenxfi3.c b/firmware/target/arm/imx233/creative-zenxfi3/button-zenxfi3.c
index 756231a..ed8e769 100644
--- a/firmware/target/arm/imx233/creative-zenxfi3/button-zenxfi3.c
+++ b/firmware/target/arm/imx233/creative-zenxfi3/button-zenxfi3.c
@@ -18,16 +18,10 @@
  * KIND, either express or implied.
  *
  ****************************************************************************/
-#include "button-target.h"
 #include "system.h"
-#include "system-target.h"
-#include "pinctrl-imx233.h"
-#include "power-imx233.h"
+#include "tick.h"
 #include "button-imx233.h"
-#include "string.h"
-#include "usb.h"
-#include "backlight.h"
-#include "mpr121.h"
+#include "mpr121-zenxfi3.h"
 
 #define I_VDDIO 0 /* index in the table */
 
@@ -42,7 +36,8 @@ struct imx233_button_map_t imx233_button_map[] =
     IMX233_BUTTON_(END, END(), "")
 };
 
-static struct mpr121_config_t config =
+/* MPR121 configuration, mostly extracted from OF */
+static struct mpr121_config_t mpr121_config =
 {
     .ele =
     {
@@ -73,74 +68,11 @@ static struct mpr121_config_t config =
     .cal_lock = CL_TRACK
 };
 
-#define MPR121_INTERRUPT    1
-
-static int touchpad_btns = 0;
-static long mpr121_stack[DEFAULT_STACK_SIZE/sizeof(long)];
-static const char mpr121_thread_name[] = "mpr121";
-static struct event_queue mpr121_queue;
-
-static void mpr121_irq_cb(int bank, int pin, intptr_t user)
-{
-    (void) bank;
-    (void) pin;
-    (void) user;
-    /* the callback will not be fired until interrupt is enabled back so
-     * the queue will not overflow or contain multiple MPR121_INTERRUPT events */
-    queue_post(&mpr121_queue, MPR121_INTERRUPT, 0);
-}
-
-static void mpr121_thread(void)
-{
-    struct queue_event ev;
-
-    while(1)
-    {
-        queue_wait(&mpr121_queue, &ev);
-        /* handle usb connect and ignore all messages except rmi interrupts */
-        if(ev.id == SYS_USB_CONNECTED)
-        {
-            usb_acknowledge(SYS_USB_CONNECTED_ACK);
-            continue;
-        }
-        else if(ev.id != MPR121_INTERRUPT)
-            continue;
-        /* clear interrupt and get status */
-        unsigned status;
-        touchpad_btns = 0;
-        if(!mpr121_get_touch_status(&status))
-        {
-            /* ELE3: up
-             * ELE4: back
-             * ELE5: menu
-             * ELE6: down
-             * ELE7: play */
-            if(status & 0x8) touchpad_btns |= BUTTON_UP;
-            if(status & 0x10) touchpad_btns |= BUTTON_BACK;
-            if(status & 0x20) touchpad_btns |= BUTTON_MENU;
-            if(status & 0x40) touchpad_btns |= BUTTON_DOWN;
-            if(status & 0x80) touchpad_btns |= BUTTON_PLAY;
-        }
-        /* enable interrupt */
-        imx233_pinctrl_setup_irq(0, 18, true, true, false, &mpr121_irq_cb, 0);
-    }
-}
-
 /* B0P18 is #IRQ line of the touchpad */
 void button_init_device(void)
 {
-    mpr121_init(0xb4);
-    mpr121_soft_reset();
-    mpr121_set_config(&config);
-
-    queue_init(&mpr121_queue, true);
-    create_thread(mpr121_thread, mpr121_stack, sizeof(mpr121_stack), 0,
-        mpr121_thread_name IF_PRIO(, PRIORITY_USER_INTERFACE) IF_COP(, CPU));
-    /* enable interrupt */
-    imx233_pinctrl_acquire(0, 18, "mpr121_int");
-    imx233_pinctrl_set_function(0, 18, PINCTRL_FUNCTION_GPIO);
-    imx233_pinctrl_enable_gpio(0, 18, false);
-    imx233_pinctrl_setup_irq(0, 18, true, true, false, &mpr121_irq_cb, 0);
+    mpr121_init();
+    mpr121_set_config(&mpr121_config);
     /* generic part */
     imx233_button_init();
 }
@@ -151,7 +83,6 @@ int button_read_device(void)
      * for one second after hold is released */
     static int power_ignore_counter = 0;
     static bool old_hold;
-    /* light handling */
     bool hold = button_hold();
     if(hold != old_hold)
     {
@@ -159,6 +90,20 @@ int button_read_device(void)
         if(!hold)
             power_ignore_counter = HZ;
     }
+    /* interpret touchpad status */
+    unsigned status = mpr121_get_touch_status();
+    unsigned touchpad_btns = 0;
+    /* ELE3: up
+     * ELE4: back
+     * ELE5: menu
+     * ELE6: down
+     * ELE7: play */
+    if(status & 0x8) touchpad_btns |= BUTTON_UP;
+    if(status & 0x10) touchpad_btns |= BUTTON_BACK;
+    if(status & 0x20) touchpad_btns |= BUTTON_MENU;
+    if(status & 0x40) touchpad_btns |= BUTTON_DOWN;
+    if(status & 0x80) touchpad_btns |= BUTTON_PLAY;
+    /* feed it to generic code */
     int res = imx233_button_read(touchpad_btns);
     if(power_ignore_counter > 0)
     {
diff --git a/firmware/target/arm/imx233/creative-zenxfi3/mpr121-zenxfi3.c b/firmware/target/arm/imx233/creative-zenxfi3/mpr121-zenxfi3.c
new file mode 100644
index 0000000..23fcc7f
--- /dev/null
+++ b/firmware/target/arm/imx233/creative-zenxfi3/mpr121-zenxfi3.c
@@ -0,0 +1,236 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2012 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.
+ *
+ ****************************************************************************/ 
+
+/** Driver for the Freescale MPR121 Capacitive Proximity Sensor */
+#include "system.h"
+#include "kernel.h"
+#include "usb.h"
+#include "mpr121.h"
+#include "mpr121-zenxfi3.h"
+#include "i2c-imx233.h"
+#include "pinctrl-imx233.h"
+
+#define MPR121_I2C_ADDR     0xb4
+
+/* NOTE on the architecture of the driver
+ *
+ * All non-time-critical operations (setup, gpio/pwm changes) are done with
+ * blocking i2c transfers to make the code simpler. Since reading the touch
+ * status is time critical, it is done asynchronously: when the IRQ pin is
+ * asserted, it will disable IRQ pin sensing and trigger an asynchronous i2c
+ * transfer to read touch status. When the transfer finishes, the driver will
+ * renable IRQ pin sensing. */
+
+static unsigned touch_status = 0; /* touch bitmask as reported by mpr121 */
+static struct imx233_i2c_xfer_t read_status_xfer; /* async transfer to read touch status */
+static uint8_t read_status_sel_reg; /* buffer for async transfer operation */
+static uint8_t read_status_buf[2]; /* buffer for async transfer operation */
+
+static void mpr121_irq_cb(int bank, int pin, intptr_t user);
+
+static void touch_status_i2c_cb(struct imx233_i2c_xfer_t *xfer, enum imx233_i2c_error_t status)
+{
+    (void) xfer;
+    (void) status;
+    /* put status in the global variable */
+    touch_status = read_status_buf[0] | read_status_buf[1] << 8;
+    /* start sensing IRQ pin again */
+    imx233_pinctrl_setup_irq(0, 18, true, true, false, &mpr121_irq_cb, 0);
+}
+
+void mpr121_irq_cb(int bank, int pin, intptr_t user)
+{
+    (void) bank;
+    (void) pin;
+    (void) user;
+    /* NOTE the callback will not be fired until interrupt is enabled back.
+     *
+     * now setup an asynchronous i2c transfer to read touch status register,
+     * this is a readmem operation with a first stage to select register
+     * and a second stage to read status (2 bytes) */
+    read_status_sel_reg = REG_TOUCH_STATUS;
+
+    read_status_xfer.next = NULL;
+    read_status_xfer.fast_mode = true;
+    read_status_xfer.dev_addr = MPR121_I2C_ADDR;
+    read_status_xfer.mode = I2C_READ;
+    read_status_xfer.count[0] = 1; /* set touch status register address */
+    read_status_xfer.data[0] = &read_status_sel_reg;
+    read_status_xfer.count[1] = 2;
+    read_status_xfer.data[1] = &read_status_buf;
+    read_status_xfer.tmo_ms = 1000;
+    read_status_xfer.callback = &touch_status_i2c_cb;
+
+    imx233_i2c_transfer(&read_status_xfer);
+}
+
+static inline int mpr121_write_reg(uint8_t reg, uint8_t data)
+{
+    return i2c_writemem(MPR121_I2C_ADDR, reg, &data, 1);
+}
+
+static inline int mpr121_read_reg(uint8_t reg, uint8_t *data)
+{
+    return i2c_readmem(MPR121_I2C_ADDR, reg, data, 1);
+}
+
+void mpr121_init(void)
+{
+    /* soft reset */
+    mpr121_write_reg(REG_SOFTRESET, REG_SOFTRESET__MAGIC);
+    /* enable interrupt */
+    imx233_pinctrl_acquire(0, 18, "mpr121_int");
+    imx233_pinctrl_set_function(0, 18, PINCTRL_FUNCTION_GPIO);
+    imx233_pinctrl_enable_gpio(0, 18, false);
+    imx233_pinctrl_setup_irq(0, 18, true, true, false, &mpr121_irq_cb, 0);
+}
+
+void mpr121_set_config(struct mpr121_config_t *conf)
+{
+    /* stop mode */
+    mpr121_write_reg(REG_ELECTRODE, 0);
+    /* write baseline values */
+    for(int i = 0; i < ELECTRODE_COUNT; i++)
+        mpr121_write_reg(REG_ExBV(i), conf->ele[i].bv);
+    /* write eleprox bv */
+    mpr121_write_reg(REG_EPROXBV, conf->eleprox.bv);
+    /* write global fields */
+    mpr121_write_reg(REG_MHDR, conf->filters.ele.rising.mhd);
+    mpr121_write_reg(REG_NHDR, conf->filters.ele.rising.nhd);
+    mpr121_write_reg(REG_NCLR, conf->filters.ele.rising.ncl);
+    mpr121_write_reg(REG_FDLR, conf->filters.ele.rising.fdl);
+    mpr121_write_reg(REG_MHDF, conf->filters.ele.falling.mhd);
+    mpr121_write_reg(REG_NHDF, conf->filters.ele.falling.nhd);
+    mpr121_write_reg(REG_NCLF, conf->filters.ele.falling.ncl);
+    mpr121_write_reg(REG_FDLF, conf->filters.ele.falling.fdl);
+    mpr121_write_reg(REG_NHDT, conf->filters.ele.touched.nhd);
+    mpr121_write_reg(REG_NCLT, conf->filters.ele.touched.ncl);
+    mpr121_write_reg(REG_FDLT, conf->filters.ele.touched.fdl);
+    mpr121_write_reg(REG_MHDPROXR, conf->filters.eleprox.rising.mhd);
+    mpr121_write_reg(REG_NHDPROXR, conf->filters.eleprox.rising.nhd);
+    mpr121_write_reg(REG_NCLPROXR, conf->filters.eleprox.rising.ncl);
+    mpr121_write_reg(REG_FDLPROXR, conf->filters.eleprox.rising.fdl);
+    mpr121_write_reg(REG_MHDPROXF, conf->filters.eleprox.falling.mhd);
+    mpr121_write_reg(REG_NHDPROXF, conf->filters.eleprox.falling.nhd);
+    mpr121_write_reg(REG_NCLPROXF, conf->filters.eleprox.falling.ncl);
+    mpr121_write_reg(REG_FDLPROXF, conf->filters.eleprox.falling.fdl);
+    mpr121_write_reg(REG_NHDPROXT, conf->filters.eleprox.touched.nhd);
+    mpr121_write_reg(REG_NCLPROXT, conf->filters.eleprox.touched.ncl);
+    mpr121_write_reg(REG_FDLPROXT, conf->filters.eleprox.touched.fdl);
+    /* touch & release thresholds */
+    for(int i = 0; i < ELECTRODE_COUNT; i++)
+    {
+        mpr121_write_reg(REG_ExTTH(i), conf->ele[i].tth);
+        mpr121_write_reg(REG_ExRTH(i), conf->ele[i].rth);
+    }
+    mpr121_write_reg(REG_EPROXTTH, conf->eleprox.tth);
+    mpr121_write_reg(REG_EPROXRTH, conf->eleprox.rth);
+    /* debounce */
+    mpr121_write_reg(REG_DEBOUNCE, REG_DEBOUNCE__DR(conf->debounce.dr) |
+        REG_DEBOUNCE__DT(conf->debounce.dt));
+    /* analog-front end and filters */
+    mpr121_write_reg(REG_AFE, REG_AFE__CDC(conf->global.cdc) |
+        REG_AFE__FFI(conf->global.ffi));
+    mpr121_write_reg(REG_FILTER, REG_FILTER__CDT(conf->global.cdt) |
+        REG_FILTER__ESI(conf->global.esi) | REG_FILTER__SFI(conf->global.sfi));
+    /* electrode charge */
+    for(int i = 0; i < ELECTRODE_COUNT; i++)
+        mpr121_write_reg(REG_CDCx(i), conf->ele[i].cdc);
+    mpr121_write_reg(REG_CDCPROX, conf->eleprox.cdc);
+    for(int i = 0; i < ELECTRODE_COUNT; i += 2)
+    {
+        mpr121_write_reg(REG_CDTx(i), REG_CDTx__CDT0(conf->ele[i].cdt) |
+            REG_CDTx__CDT1(conf->ele[i+1].cdt));
+    }
+    mpr121_write_reg(REG_CDTPROX, conf->eleprox.cdt);
+    /* Auto-Configuration */
+    mpr121_write_reg(REG_AUTO_CONF, REG_AUTO_CONF__ACE(conf->autoconf.en) |
+        REG_AUTO_CONF__ARE(conf->autoconf.ren) |
+        REG_AUTO_CONF__BVA(conf->cal_lock) |
+        REG_AUTO_CONF__RETRY(conf->autoconf.retry) |
+        REG_AUTO_CONF__FFI(conf->global.ffi));
+    mpr121_write_reg(REG_AUTO_CONF2, REG_AUTO_CONF2__ACFIE(conf->autoconf.acfie) |
+        REG_AUTO_CONF2__ARFIE(conf->autoconf.arfie) |
+        REG_AUTO_CONF2__OORIE(conf->autoconf.oorie) |
+        REG_AUTO_CONF2__SCTS(conf->autoconf.scts));
+    mpr121_write_reg(REG_USL, conf->autoconf.usl);
+    mpr121_write_reg(REG_LSL, conf->autoconf.lsl);
+    mpr121_write_reg(REG_TL, conf->autoconf.tl);
+    /* electrode configuration */
+    mpr121_write_reg(REG_ELECTRODE, REG_ELECTRODE__ELE_EN(conf->ele_en) |
+        REG_ELECTRODE__ELEPROX_EN(conf->eleprox_en) |
+        REG_ELECTRODE__CL(conf->cal_lock));
+    /* gpio config */
+    uint8_t ctl = 0;
+    for(int i = ELE_GPIO_FIRST; i <= ELE_GPIO_LAST; i++)
+        if(ELE_GPIO_CTL0(conf->ele[i].gpio))
+            ctl |= REG_GPIO_CTL0__CTL0x(i);
+    mpr121_write_reg(REG_GPIO_CTL0, ctl);
+    ctl = 0;
+    for(int i = ELE_GPIO_FIRST; i <= ELE_GPIO_LAST; i++)
+        if(ELE_GPIO_CTL1(conf->ele[i].gpio))
+            ctl |= REG_GPIO_CTL1__CTL1x(i);
+    mpr121_write_reg(REG_GPIO_CTL1, ctl);
+    ctl = 0;
+    for(int i = ELE_GPIO_FIRST; i <= ELE_GPIO_LAST; i++)
+        if(ELE_GPIO_DIR(conf->ele[i].gpio))
+            ctl |= REG_GPIO_DIR__DIRx(i);
+    mpr121_write_reg(REG_GPIO_DIR, ctl);
+    ctl = 0;
+    for(int i = ELE_GPIO_FIRST; i <= ELE_GPIO_LAST; i++)
+        if(ELE_GPIO_EN(conf->ele[i].gpio))
+            ctl |= REG_GPIO_EN__ENx(i);
+    mpr121_write_reg(REG_GPIO_EN, ctl);
+}
+
+void mpr121_set_gpio_output(int ele, int gpio_val)
+{
+    switch(gpio_val)
+    {
+        case ELE_GPIO_SET:
+            mpr121_write_reg(REG_GPIO_SET, REG_GPIO_SET__SETx(ele));
+            break;
+        case ELE_GPIO_CLR:
+            mpr121_write_reg(REG_GPIO_CLR, REG_GPIO_CLR__CLRx(ele));
+            break;
+        case ELE_GPIO_TOG:
+            mpr121_write_reg(REG_GPIO_TOG, REG_GPIO_TOG__TOGx(ele));
+            break;
+        default:
+            break;
+    }
+}
+
+void mpr121_set_gpio_pwm(int ele, int pwm)
+{
+    uint8_t reg_val;
+    mpr121_read_reg(REG_PWMx(ele), &reg_val);
+    if(REG_PWMx_IS_PWM0(ele))
+        reg_val = (reg_val & ~REG_PWMx__PWM0_BM) | REG_PWMx__PWM0(pwm);
+    else
+        reg_val = (reg_val & ~REG_PWMx__PWM1_BM) | REG_PWMx__PWM1(pwm);
+    mpr121_write_reg(REG_PWMx(ele), reg_val);
+}
+
+unsigned mpr121_get_touch_status(void)
+{
+    return touch_status;
+}
diff --git a/firmware/target/arm/imx233/creative-zenxfi3/mpr121-zenxfi3.h b/firmware/target/arm/imx233/creative-zenxfi3/mpr121-zenxfi3.h
new file mode 100644
index 0000000..eb8b00e
--- /dev/null
+++ b/firmware/target/arm/imx233/creative-zenxfi3/mpr121-zenxfi3.h
@@ -0,0 +1,176 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2016 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 __MPR121_ZENXFI3_H__
+#define __MPR121_ZENXFI3_H__
+
+/** Driver for the Freescale MPR121 Capacitive Proximity Sensor */
+#include "system.h"
+
+#define ELECTRODE_COUNT 12
+#define ELE_GPIO_FIRST  4
+#define ELE_GPIO_LAST   11
+
+/* gpio config (encoding: [0]=en,[1]=dir,[2]=ctl[1],[3]=ctl[0]) */
+#define ELE_GPIO_DISABLE        0
+#define ELE_GPIO_INPUT          1
+#define ELE_GPIO_INPUT_PULLDOWN 9 /* input with pull-down */
+#define ELE_GPIO_INPUT_PULLUP   13 /* input with pull-up */
+#define ELE_GPIO_OUTPUT         3
+#define ELE_GPIO_OUTPUT_OPEN     11 /* open drain low-side */
+#define ELE_GPIO_OUTPUT_OPEN_LED 15 /* open drain high-side (led driver) */
+
+/* internal use */
+#define ELE_GPIO_EN(val)    ((val) & 1)
+#define ELE_GPIO_DIR(val)   (((val) >> 1) & 1)
+#define ELE_GPIO_CTL0(val)  (((val) >> 3) & 1)
+#define ELE_GPIO_CTL1(val)  (((val) >> 1) & 1)
+
+struct mpr121_electrode_config_t
+{
+    uint8_t bv; /* baseline value */
+    uint8_t tth; /* touch threshold */
+    uint8_t rth; /* release threshold */
+    uint8_t cdc; /* charge current (optional if auto-conf) */
+    uint8_t cdt; /* charge time (optional if auto-conf) */
+    int gpio; /* gpio config */
+};
+
+struct mpr121_baseline_filter_config_t
+{
+    uint8_t mhd; /* max half delta (except for touched) */
+    uint8_t nhd; /* noise half delta */
+    uint8_t ncl; /* noise count limit */
+    uint8_t fdl; /* filter delay count limit */
+};
+
+struct mpr121_baseline_filters_config_t
+{
+    struct mpr121_baseline_filter_config_t rising;
+    struct mpr121_baseline_filter_config_t falling;
+    struct mpr121_baseline_filter_config_t touched;
+};
+
+struct mpr121_debounce_config_t
+{
+    uint8_t dt; /* debounce count for touch */
+    uint8_t dr; /* debounce count for release */
+};
+
+/* first filter iterations */
+#define FFI_6_SAMPLES   0
+#define FFI_10_SAMPLES  1
+#define FFI_18_SAMPLES  2
+#define FFI_34_SAMPLES  3
+/* charge discharge current */
+#define CDC_DISABLE     0
+#define CDC_uA(ua)      (ua)
+/* charge discharge time */
+#define CDT_DISABLE     0
+#define CDT_log_us(lus) (lus) /* actual value = 2^{us-2} µs */
+/* second filter iterations */
+#define SFI_4_SAMPLES   0
+#define SFI_6_SAMPLES   1
+#define SFI_10_SAMPLES  2
+#define SFI_18_SAMPLES  3
+/* Eletrode sample interval */
+#define ESI_log_ms(lms) (lms) /* actual value = 2^{lms} ms */
+
+struct mpr121_global_config_t
+{
+    uint8_t ffi; /* first filter iterations */
+    uint8_t cdc; /* global charge discharge current */
+    uint8_t cdt; /* global charge discharge time */
+    uint8_t sfi; /* second first iterations */
+    uint8_t esi; /* electrode sample interval */
+};
+
+#define RETRY_NEVER     0
+#define RETRY_2_TIMES   1
+#define RETRY_4_TIMES   2
+#define RETRY_8_TIMES   3
+
+struct mpr121_auto_config_t
+{
+    bool en; /* auto-conf enable */
+    bool ren; /* auto-reconf enable */
+    uint8_t retry; /* retry count */
+    bool scts; /* skip charge time search */
+    uint8_t usl; /* upper-side limit */
+    uint8_t lsl; /* lower-side limit */
+    uint8_t tl; /* target level */
+    bool acfie; /* auto-conf fail interrupt en */
+    bool arfie; /* auto-reconf fail interrupt en */
+    bool oorie; /* out of range interrupt en */
+};
+
+/* electrode mode */
+#define ELE_DISABLE     0
+#define ELE_EN0_x(x)    ((x) + 1)
+/* eleprox mode */
+#define ELEPROX_DISABLE 0
+#define ELEPROX_EN0_1   1
+#define ELEPROX_EN0_3   2
+#define ELEPROX_EN0_11  3
+/* calibration lock */
+#define CL_SLOW_TRACK   0
+#define CL_DISABLE      1
+#define CL_TRACK        2
+#define CL_FAST_TRACK   3
+
+struct mpr121_config_t
+{
+    struct mpr121_electrode_config_t ele[ELECTRODE_COUNT];
+    struct mpr121_electrode_config_t eleprox;
+    struct
+    {
+        struct mpr121_baseline_filters_config_t ele;
+        struct mpr121_baseline_filters_config_t eleprox;
+    }filters;
+    struct mpr121_debounce_config_t debounce;
+    struct mpr121_global_config_t global;
+    struct mpr121_auto_config_t autoconf;
+    uint8_t ele_en; /* eletroce mode */
+    uint8_t eleprox_en; /* proximity mode */
+    uint8_t cal_lock; /* calibration lock */
+};
+
+/* gpio value */
+#define ELE_GPIO_CLR    0
+#define ELE_GPIO_SET    1
+#define ELE_GPIO_TOG    2
+/* pwm value */
+#define ELE_PWM_DISABLE 0
+#define ELE_PWM_DUTY(x) (x)
+#define ELE_PWM_MIN_DUTY    1
+#define ELE_PWM_MAX_DUTY    15
+
+void mpr121_init(void);
+void mpr121_set_config(struct mpr121_config_t *conf);
+/* gpios are only implemented for electrode>=4, use ELE_GPIO_* for value */
+void mpr121_set_gpio_output(int ele, int gpio_val);
+/* pwm value is between 0 and 15, use ELE_PWM_DISABLE or ELE_PWM_DUTY */
+void mpr121_set_gpio_pwm(int ele, int pwm);
+/* get electrode status (bitmap)
+ * NOTE this function merely returns the last electrode status read from the
+ * device and does not actively ask the device for touch status. */
+unsigned mpr121_get_touch_status(void);
+
+#endif /* __MPR121_ZENXFI3_H__ */