Input: ads7846 - optionally leave Vref on during differential measurements
On some LCDs leaving the Vref on provides much better readings.
Signed-off-by: Jarkko Oikarinen <jarkko.oikarinen@nokia.com>
Signed-off-by: Imre Deak <imre.deak@solidboot.com>
Signed-off-by: Juha Yrjola <juha.yrjola@solidboot.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 03e527c..c34e59b 100644
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -145,15 +145,16 @@
#define MAX_12BIT ((1<<12)-1)
/* leave ADC powered up (disables penirq) between differential samples */
-#define READ_12BIT_DFR(x) (ADS_START | ADS_A2A1A0_d_ ## x \
- | ADS_12_BIT | ADS_DFR)
+#define READ_12BIT_DFR(x, adc, vref) (ADS_START | ADS_A2A1A0_d_ ## x \
+ | ADS_12_BIT | ADS_DFR | \
+ (adc ? ADS_PD10_ADC_ON : 0) | (vref ? ADS_PD10_REF_ON : 0))
-#define READ_Y (READ_12BIT_DFR(y) | ADS_PD10_ADC_ON)
-#define READ_Z1 (READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON)
-#define READ_Z2 (READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON)
+#define READ_Y(vref) (READ_12BIT_DFR(y, 1, vref))
+#define READ_Z1(vref) (READ_12BIT_DFR(z1, 1, vref))
+#define READ_Z2(vref) (READ_12BIT_DFR(z2, 1, vref))
-#define READ_X (READ_12BIT_DFR(x) | ADS_PD10_ADC_ON)
-#define PWRDOWN (READ_12BIT_DFR(y) | ADS_PD10_PDOWN) /* LAST */
+#define READ_X(vref) (READ_12BIT_DFR(x, 1, vref))
+#define PWRDOWN (READ_12BIT_DFR(y, 0, 0)) /* LAST */
/* single-ended samples need to first power up reference voltage;
* we leave both ADC and VREF powered
@@ -161,8 +162,8 @@
#define READ_12BIT_SER(x) (ADS_START | ADS_A2A1A0_ ## x \
| ADS_12_BIT | ADS_SER)
-#define REF_ON (READ_12BIT_DFR(x) | ADS_PD10_ALL_ON)
-#define REF_OFF (READ_12BIT_DFR(y) | ADS_PD10_PDOWN)
+#define REF_ON (READ_12BIT_DFR(x, 1, 1))
+#define REF_OFF (READ_12BIT_DFR(y, 0, 0))
/*--------------------------------------------------------------------------*/
@@ -670,6 +671,7 @@
struct ads7846_platform_data *pdata = spi->dev.platform_data;
struct spi_message *m;
struct spi_transfer *x;
+ int vref;
int err;
if (!spi->irq) {
@@ -767,6 +769,8 @@
input_set_abs_params(input_dev, ABS_PRESSURE,
pdata->pressure_min, pdata->pressure_max, 0, 0);
+ vref = pdata->keep_vref_on;
+
/* set up the transfers to read touchscreen state; this assumes we
* use formula #2 for pressure, not #3.
*/
@@ -776,7 +780,7 @@
spi_message_init(m);
/* y- still on; turn on only y+ (and ADC) */
- ts->read_y = READ_Y;
+ ts->read_y = READ_Y(vref);
x->tx_buf = &ts->read_y;
x->len = 1;
spi_message_add_tail(x, m);
@@ -794,7 +798,7 @@
/* turn y- off, x+ on, then leave in lowpower */
x++;
- ts->read_x = READ_X;
+ ts->read_x = READ_X(vref);
x->tx_buf = &ts->read_x;
x->len = 1;
spi_message_add_tail(x, m);
@@ -813,7 +817,7 @@
spi_message_init(m);
x++;
- ts->read_z1 = READ_Z1;
+ ts->read_z1 = READ_Z1(vref);
x->tx_buf = &ts->read_z1;
x->len = 1;
spi_message_add_tail(x, m);
@@ -830,7 +834,7 @@
spi_message_init(m);
x++;
- ts->read_z2 = READ_Z2;
+ ts->read_z2 = READ_Z2(vref);
x->tx_buf = &ts->read_z2;
x->len = 1;
spi_message_add_tail(x, m);