190 lines
6.6 KiB
C
190 lines
6.6 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2012 by Amaury Pouly
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#include "touchscreen-imx233.h"
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#include "stdlib.h"
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/* Description:
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* the driver basically has 2 modes:
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* - wait mode: use the hardware touch detect mechanism to wait for an edge
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* - measurement mode: use pull up/down and adc to measure X/Y
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* In measurement mode, we start by measuring X then Y then we check if
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* the hardware still detect a touch. When no touch is detected anymore, we
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* go back to wait mode.
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* For each axis, we handle stabilization by repeatedly measuring the position
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* until it is stable. We consider a set of measures stable when
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* no measure is further away from the average than DEBOUNCE_THRESHOLD and
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* we have at least SAMPLES_THRESHOLD measures. This avoids using magic
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* timing constants specific to the touchscreen stabilization time and
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* it is much more robust.
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*
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* Inspired by linux touchscreen driver for the stmp37xx.
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*/
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enum touch_state_t
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{
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TOUCH_STATE_WAIT, /* wait for touch */
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TOUCH_STATE_MEASURE_X, /* measure x */
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TOUCH_STATE_MEASURE_Y, /* measure y */
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TOUCH_STATE_VERIFY, /* verify touch */
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};
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#define DEBOUNCE_THRESHOLD 100
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#define SAMPLES_THRESHOLD 4
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static enum touch_state_t touch_state;
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static int touch_chan = -1;
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static int touch_delay = -1;
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static int touch_x, touch_y, nr_samples;
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/* once a touch is confirmed, the parameters are copied to these value for
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* instant readout by button code. */
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static bool old_touch_detect = false;
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static int old_touch_x, old_touch_y;
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static void kick_measure(bool pull_x, bool pull_y, bool detect, int lradc_phys)
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{
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/* setup measurement: x- pull down and x+ pull up */
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imx233_lradc_setup_touch(pull_x, pull_y, pull_x, pull_y, detect);
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imx233_lradc_enable_touch_detect_irq(false);
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imx233_lradc_enable_channel_irq(touch_chan, true);
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/* measure channel, no accumulation */
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imx233_lradc_setup_channel(touch_chan, false, false, 0, lradc_phys);
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/* use a delay */
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imx233_lradc_setup_delay(touch_delay, 1 << touch_chan, 0, 0, 8);
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imx233_lradc_kick_delay(touch_delay);
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}
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static void enter_state(enum touch_state_t state)
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{
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touch_state = state;
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switch(state)
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{
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case TOUCH_STATE_WAIT:
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imx233_lradc_setup_touch(false, false, false, false, true);
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imx233_lradc_enable_channel_irq(touch_chan, false);
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imx233_lradc_enable_touch_detect_irq(true);
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break;
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case TOUCH_STATE_MEASURE_X:
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kick_measure(true, false, false, LRADC_SRC_YPLUS);
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break;
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case TOUCH_STATE_MEASURE_Y:
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kick_measure(false, true, false, LRADC_SRC_XPLUS);
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break;
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case TOUCH_STATE_VERIFY:
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kick_measure(false, false, true, LRADC_SRC_YPLUS);
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break;
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}
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}
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static void process(void)
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{
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int val;
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switch(touch_state)
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{
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case TOUCH_STATE_WAIT:
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/* a touch has happened, check if it's still valid */
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if(imx233_lradc_read_touch_detect())
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enter_state(TOUCH_STATE_MEASURE_X);
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else
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{
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old_touch_detect = false;
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/* clear detect interrupt */
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imx233_lradc_clear_touch_detect_irq();
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}
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break;
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case TOUCH_STATE_MEASURE_X:
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/* read value */
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val = imx233_lradc_read_channel(touch_chan);
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/* if value is too far from average, restart */
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if(nr_samples > 0 && abs(val - touch_x) > DEBOUNCE_THRESHOLD)
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nr_samples = 0;
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touch_x = (touch_x * nr_samples + val) / (nr_samples + 1);
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nr_samples++;
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/* if we have enough samples, measure Y */
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if(nr_samples > SAMPLES_THRESHOLD)
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enter_state(TOUCH_STATE_MEASURE_Y);
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else
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imx233_lradc_kick_delay(touch_delay);
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break;
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case TOUCH_STATE_MEASURE_Y:
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/* read value */
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val = imx233_lradc_read_channel(touch_chan);
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/* if value is too far from average, restart */
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if(nr_samples > 0 && abs(val - touch_y) > DEBOUNCE_THRESHOLD)
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nr_samples = 0;
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touch_y = (touch_y * nr_samples + val) / (nr_samples + 1);
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nr_samples++;
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/* if we have enough samples, verify touch */
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if(nr_samples > SAMPLES_THRESHOLD)
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enter_state(TOUCH_STATE_VERIFY);
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else
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imx233_lradc_kick_delay(touch_delay);
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break;
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case TOUCH_STATE_VERIFY:
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if(imx233_lradc_read_touch_detect())
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{
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old_touch_detect = true;
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old_touch_x = touch_x;
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old_touch_y = touch_y;
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enter_state(TOUCH_STATE_MEASURE_X);
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}
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else
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{
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old_touch_detect = false;
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enter_state(TOUCH_STATE_WAIT);
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}
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break;
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}
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}
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void INT_TOUCH_DETECT(void)
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{
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process();
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}
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static void touch_channel_irq(int chan)
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{
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(void) chan;
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process();
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}
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void imx233_touchscreen_init(void)
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{
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touch_chan = imx233_lradc_acquire_channel(TIMEOUT_NOBLOCK);
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touch_delay = imx233_lradc_acquire_delay(TIMEOUT_NOBLOCK);
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if(touch_chan < 0 || touch_delay < 0)
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panicf("Cannot acquire channel and delays for touchscreen measurement");
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imx233_touchscreen_enable(false);
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}
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void imx233_touchscreen_enable(bool enable)
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{
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enter_state(TOUCH_STATE_WAIT);
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imx233_lradc_set_channel_irq_callback(touch_chan, &touch_channel_irq);
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imx233_icoll_enable_interrupt(INT_SRC_LRADC_CHx(touch_chan), enable);
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imx233_icoll_enable_interrupt(INT_SRC_TOUCH_DETECT, enable);
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}
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bool imx233_touchscreen_get_touch(int *raw_x, int *raw_y)
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{
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if(raw_x) *raw_x = old_touch_x;
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if(raw_y) *raw_y = old_touch_y;
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return old_touch_detect;
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}
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