Re: Hi guys, does any of you have experience with touchscreen controllers?

[Dale <dlarson42@gmail.com>]

Fabio Giovagnini wrote:
> I'm working with ADS7843 and I have some troubles to get only the push event 
> on the screen.
> If any of you knows a better place where to talk about this argument it will 
> be appreciated very much to tell me.
> 
> Best regards

Hi Fabio,

I've dealt with that chip for our 7760 board. The key is to provide a pen
poll function so pen up can be detected. Here's the way I defined it in the
platform bsp stuff:

:
:
#include <linux/spi/spi.h>
#include <linux/spi/ads7846.h>
:
:
/* SPI devices - Touch Screen */

static int ads7843_pendown_state(void)
{
      return (ctrl_inb(PGDR) & 0x40) ? 0 : 1;
}

static struct ads7846_platform_data ads_info = {
     .model              = 7843,
     .x_min              = 150,
     .x_max              = 3830,
     .y_min              = 190,
     .y_max              = 3830,
     .vref_delay_usecs   = 100,
     .keep_vref_on       = 1,
     .x_plate_ohms       = 576,
     .y_plate_ohms       = 366,
     .pressure_max       = 15000,    /* Generally nonsense on the 7843 */
     .debounce_max       = 1,
     .debounce_rep       = 0,
     .debounce_tol       = (~0),
     .get_pendown_state  = ads7843_pendown_state,
};

static struct spi_board_info jcinap_spi_devices[] = {
     {
         /* Touchscreen controller */
         .modalias       = "ads7846",
         .chip_select    = 0,
         .bus_num        = 0,
         .max_speed_hz   = 1000000,   /* 1Mhz */
         .platform_data  = &ads_info,
         .irq            = 11
     },
};
:
:

In the init code:

:
:
/* Register the SPI devices */
spi_register_board_info(jcinap_spi_devices, ARRAY_SIZE(jcinap_spi_devices));
:
:

Dale Larson
Johnson Controls, Inc