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Input: ads7846 - power down ADC a bit later

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Submit a seperate request for powering down the ADC in ads7846,
doing it after the last read request.  Otherwise some of the read
values are incorrect.

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>
This commit is contained in:
Imre Deak 2006-04-11 23:41:49 -04:00 committed by Dmitry Torokhov
parent 438f2a7401
commit 53a0ef89e9
1 changed files with 18 additions and 3 deletions
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21
drivers/input/touchscreen/ads7846.c
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@ -72,10 +72,11 @@ struct ads7846 {
u16 vref_delay_usecs;
u16 x_plate_ohms;
u8 read_x, read_y, read_z1, read_z2;
u8 read_x, read_y, read_z1, read_z2, pwrdown;
u16 dummy; /* for the pwrdown read */
struct ts_event tc;
struct spi_transfer xfer[8];
struct spi_transfer xfer[10];
struct spi_message msg;
spinlock_t lock;
@ -125,7 +126,9 @@ struct ads7846 {
#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_X (READ_12BIT_DFR(x) | ADS_PD10_PDOWN) /* LAST */
#define READ_X (READ_12BIT_DFR(x) | ADS_PD10_ADC_ON)
#define PWRDOWN (READ_12BIT_DFR(y) | ADS_PD10_PDOWN) /* LAST */
/* single-ended samples need to first power up reference voltage;
* we leave both ADC and VREF powered
@ -541,6 +544,18 @@ static int __devinit ads7846_probe(struct spi_device *spi)
x++;
x->rx_buf = &ts->tc.x;
x->len = 2;
spi_message_add_tail(x, &ts->msg);
/* power down */
x++;
ts->pwrdown = PWRDOWN;
x->tx_buf = &ts->pwrdown;
x->len = 1;
spi_message_add_tail(x, &ts->msg);
x++;
x->rx_buf = &ts->dummy;
x->len = 2;
CS_CHANGE(*x);
spi_message_add_tail(x, &ts->msg);