Skip to content

Commit

Permalink
Input: ads7846 - debouncing and rudimentary sample filtering
Browse files Browse the repository at this point in the history 
Some touchscreens seem to oscillate heavily for a while after touching
the screen.  Implement support for sampling the screen until we get two
consecutive values that are close enough.

Signed-off-by: Imre Deak <imre.deak@nokia.com>
Signed-off-by: Juha Yrjola <juha.yrjola@nokia.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
  • Loading branch information
Imre Deak authored and Dmitry Torokhov committed Apr 12, 2006
1 parent 53a0ef8 commit 0b7018a
Show file tree
Hide file tree
Showing 2 changed files with 121 additions and 38 deletions.
156 changes: 118 additions & 38 deletions drivers/input/touchscreen/ads7846.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,13 @@ struct ads7846 {
struct ts_event tc;

struct spi_transfer xfer[10];
struct spi_message msg;
struct spi_message msg[5];
int msg_idx;
int read_cnt;
int last_read;

u16 debounce_max;
u16 debounce_tol;

spinlock_t lock;
struct timer_list timer; /* P: lock */
Expand Down Expand Up @@ -167,7 +173,7 @@ static int ads7846_read12_ser(struct device *dev, unsigned command)
if (!req)
return -ENOMEM;

INIT_LIST_HEAD(&req->msg.transfers);
spi_message_init(&req->msg);

/* activate reference, so it has time to settle; */
req->ref_on = REF_ON;
Expand Down Expand Up @@ -344,31 +350,76 @@ static void ads7846_rx(void *ads)
spin_unlock_irqrestore(&ts->lock, flags);
}

static void ads7846_debounce(void *ads)
{
struct ads7846 *ts = ads;
struct spi_message *m;
struct spi_transfer *t;
u16 val;
int status;

m = &ts->msg[ts->msg_idx];
t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
val = (*(u16 *)t->rx_buf) >> 3;

if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol
&& ts->read_cnt < ts->debounce_max)) {
/* Repeat it, if this was the first read or the read wasn't
* consistent enough
*/
ts->read_cnt++;
ts->last_read = val;
} else {
/* Go for the next read */
ts->msg_idx++;
ts->read_cnt = 0;
m++;
}
status = spi_async(ts->spi, m);
if (status)
dev_err(&ts->spi->dev, "spi_async --> %d\n",
status);
}

static void ads7846_timer(unsigned long handle)
{
struct ads7846 *ts = (void *)handle;
int status = 0;
unsigned long flags;

ts->msg_idx = 0;
status = spi_async(ts->spi, &ts->msg[0]);
if (status)
dev_err(&ts->spi->dev, "spi_async --> %d\n", status);
}

static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
{
struct ads7846 *ts = handle;
unsigned long flags;
int r = IRQ_HANDLED;

spin_lock_irqsave(&ts->lock, flags);
if (!ts->pending) {
ts->pending = 1;
if (ts->irq_disabled)
r = IRQ_HANDLED;
else {
if (!ts->irq_disabled) {
/* REVISIT irq logic for many ARM chips has cloned a
* bug wherein disabling an irq in its handler won't
* work;(it's disabled lazily, and too late to work.
* until all their irq logic is fixed, we must shadow
* that state here.
*/
ts->irq_disabled = 1;

disable_irq(ts->spi->irq);
}
status = spi_async(ts->spi, &ts->msg);
if (status)
dev_err(&ts->spi->dev, "spi_async --> %d\n",
status);
if (!ts->pending) {
ts->pending = 1;
mod_timer(&ts->timer, jiffies);
}
}
spin_unlock_irqrestore(&ts->lock, flags);
}

static irqreturn_t ads7846_irq(int irq, void *handle, struct pt_regs *regs)
{
ads7846_timer((unsigned long) handle);
return IRQ_HANDLED;
return r;
}

/*--------------------------------------------------------------------------*/
Expand Down Expand Up @@ -426,6 +477,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
struct ads7846 *ts;
struct input_dev *input_dev;
struct ads7846_platform_data *pdata = spi->dev.platform_data;
struct spi_message *m;
struct spi_transfer *x;
int err;

Expand Down Expand Up @@ -472,6 +524,8 @@ static int __devinit ads7846_probe(struct spi_device *spi)
ts->model = pdata->model ? : 7846;
ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
ts->debounce_max = pdata->debounce_max ? : 1;
ts->debounce_tol = pdata->debounce_tol ? : 10;

snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);

Expand All @@ -495,72 +549,98 @@ static int __devinit ads7846_probe(struct spi_device *spi)
/* set up the transfers to read touchscreen state; this assumes we
* use formula #2 for pressure, not #3.
*/
INIT_LIST_HEAD(&ts->msg.transfers);
m = &ts->msg[0];
x = ts->xfer;

spi_message_init(m);

/* y- still on; turn on only y+ (and ADC) */
ts->read_y = READ_Y;
x->tx_buf = &ts->read_y;
x->len = 1;
spi_message_add_tail(x, &ts->msg);
spi_message_add_tail(x, m);

x++;
x->rx_buf = &ts->tc.y;
x->len = 2;
spi_message_add_tail(x, &ts->msg);
spi_message_add_tail(x, m);

m->complete = ads7846_debounce;
m->context = ts;

m++;
spi_message_init(m);

/* turn y- off, x+ on, then leave in lowpower */
x++;
ts->read_x = READ_X;
x->tx_buf = &ts->read_x;
x->len = 1;
spi_message_add_tail(x, m);

x++;
x->rx_buf = &ts->tc.x;
x->len = 2;
spi_message_add_tail(x, m);

m->complete = ads7846_debounce;
m->context = ts;

/* turn y+ off, x- on; we'll use formula #2 */
if (ts->model == 7846) {
m++;
spi_message_init(m);

x++;
ts->read_z1 = READ_Z1;
x->tx_buf = &ts->read_z1;
x->len = 1;
spi_message_add_tail(x, &ts->msg);
spi_message_add_tail(x, m);

x++;
x->rx_buf = &ts->tc.z1;
x->len = 2;
spi_message_add_tail(x, &ts->msg);
spi_message_add_tail(x, m);

m->complete = ads7846_debounce;
m->context = ts;

m++;
spi_message_init(m);

x++;
ts->read_z2 = READ_Z2;
x->tx_buf = &ts->read_z2;
x->len = 1;
spi_message_add_tail(x, &ts->msg);
spi_message_add_tail(x, m);

x++;
x->rx_buf = &ts->tc.z2;
x->len = 2;
spi_message_add_tail(x, &ts->msg);
}
spi_message_add_tail(x, m);

/* turn y- off, x+ on, then leave in lowpower */
x++;
ts->read_x = READ_X;
x->tx_buf = &ts->read_x;
x->len = 1;
spi_message_add_tail(x, &ts->msg);

x++;
x->rx_buf = &ts->tc.x;
x->len = 2;
spi_message_add_tail(x, &ts->msg);
m->complete = ads7846_debounce;
m->context = ts;
}

/* power down */
m++;
spi_message_init(m);

x++;
ts->pwrdown = PWRDOWN;
x->tx_buf = &ts->pwrdown;
x->len = 1;
spi_message_add_tail(x, &ts->msg);
spi_message_add_tail(x, m);

x++;
x->rx_buf = &ts->dummy;
x->len = 2;
CS_CHANGE(*x);
spi_message_add_tail(x, &ts->msg);
spi_message_add_tail(x, m);

ts->msg.complete = ads7846_rx;
ts->msg.context = ts;
m->complete = ads7846_rx;
m->context = ts;

if (request_irq(spi->irq, ads7846_irq,
SA_SAMPLE_RANDOM | SA_TRIGGER_FALLING,
Expand Down
3 changes: 3 additions & 0 deletions include/linux/spi/ads7846.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,5 +14,8 @@ struct ads7846_platform_data {
u16 x_min, x_max;
u16 y_min, y_max;
u16 pressure_min, pressure_max;

u16 debounce_max; /* max number of readings per sample */
u16 debounce_tol; /* tolerance used for filtering */
};

0 comments on commit 0b7018a

Please sign in to comment.