e4f4886199
The ads7846 driver has support for filtering, but when the chip gets deselected between samples this causes noise. This patch adds support for an optional settling delay time, so that two consecutive samples will be taken with the specified delay time apart. This ensures that the chip won't be deselected, so the noise won't appear. Filtering can still be done, but will have less work to do since each time a new sample is taken the same delay applies. Signed-off-by: Semih Hazar <semih.hazar@indefia.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
46 lines
1.3 KiB
C
46 lines
1.3 KiB
C
/* linux/spi/ads7846.h */
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/* Touchscreen characteristics vary between boards and models. The
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* platform_data for the device's "struct device" holds this information.
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*
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* It's OK if the min/max values are zero.
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*/
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enum ads7846_filter {
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ADS7846_FILTER_OK,
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ADS7846_FILTER_REPEAT,
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ADS7846_FILTER_IGNORE,
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};
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struct ads7846_platform_data {
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u16 model; /* 7843, 7845, 7846. */
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u16 vref_delay_usecs; /* 0 for external vref; etc */
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int keep_vref_on:1; /* set to keep vref on for differential
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* measurements as well */
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/* Settling time of the analog signals; a function of Vcc and the
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* capacitance on the X/Y drivers. If set to non-zero, two samples
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* are taken with settle_delay us apart, and the second one is used.
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* ~150 uSec with 0.01uF caps.
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*/
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u16 settle_delay_usecs;
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u16 x_plate_ohms;
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u16 y_plate_ohms;
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u16 x_min, x_max;
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u16 y_min, y_max;
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u16 pressure_min, pressure_max;
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u16 debounce_max; /* max number of additional readings
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* per sample */
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u16 debounce_tol; /* tolerance used for filtering */
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u16 debounce_rep; /* additional consecutive good readings
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* required after the first two */
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int (*get_pendown_state)(void);
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int (*filter_init) (struct ads7846_platform_data *pdata,
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void **filter_data);
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int (*filter) (void *filter_data, int data_idx, int *val);
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void (*filter_cleanup)(void *filter_data);
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};
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