Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit de2defd9 authored by Imre Deak's avatar Imre Deak Committed by Dmitry Torokhov
Browse files

Input: ads7846 - optionally leave Vref on during differential measurements 



On some LCDs leaving the Vref on provides much better readings.

Signed-off-by: default avatarJarkko Oikarinen <jarkko.oikarinen@nokia.com>
Signed-off-by: default avatarImre Deak <imre.deak@solidboot.com>
Signed-off-by: default avatarJuha Yrjola <juha.yrjola@solidboot.com>
Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
parent da970e69

drivers/input/touchscreen/ads7846.c

+17 −13
Original line number Diff line number Diff line
@@ -145,15 +145,16 @@ struct ads7846 { 
#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 @@ struct ads7846 { 
#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 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
	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 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
	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 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
	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 @@ static int __devinit ads7846_probe(struct spi_device *spi) 


	/* 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 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
		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 @@ static int __devinit ads7846_probe(struct spi_device *spi) 
		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);

include/linux/spi/ads7846.h

+2 −0
Original line number Diff line number Diff line
@@ -14,6 +14,8 @@ enum ads7846_filter { 
struct ads7846_platform_data {

	u16	model;			/* 7843, 7845, 7846. */

	u16	vref_delay_usecs;	/* 0 for external vref; etc */

	int	keep_vref_on:1;		/* set to keep vref on for differential

					 * measurements as well */

	u16	x_plate_ohms;

	u16	y_plate_ohms;