ads7846: enable usage of internal vref for AD7873
Subsystems (2)
PATCH 1/1 ads7846: enable usage of internal vref for AD7873
Touchscreen samples are taken in differential mode. Therefore an external reference is not needed.
When working with internal vref disabling vref after every touchscreen sample leads to settling effects in sampling and errors in position data.
This patch disables the internal vref only if keep_vref_on us is not set in platform_data.
Tested on i.MX35 with costum board
--- drivers/input/touchscreen/ads7846.c | 9 ++++----- 1 files changed, 4 insertions(+), 5 deletions(-)
drivers/input/touchscreen/ads7846.c +4 -5
@@ -1001,15 +1001,14 @@ static void __devinit ads7846_setup_spi_msg(struct ads7846 *ts,struct ads7846_packet *packet = ts->packet;int vref = pdata->keep_vref_on; -if (ts->model ==7873 ) { +if (ts->model ==7873 )/* * The AD7873 is almost identical to the ADS7846 -* keep VREF off during differential/ratiometric -* conversion modes. +* set VREF off during differential/ratiometric +* conversion modes if keep_vref_on is not set. +* TODO: does keep_vref_on collide with usage of external vref? */ ts->model =7846 ; - vref =0 ; - } ts->msg_count =1 ;spi_message_init (m);
Signature · 1 line
1.7.0.4
Quoted 28 lines · Markus Niebel
Touchscreen samples are taken in differential mode. Therefore an external reference is not needed.
When working with internal vref disabling vref after every touchscreen sample leads to settling effects in sampling and errors in position data.This patch disables the internal vref only if
keep_vref_onus is not set inplatform_data.Tested on i.MX35 with costum board
Signed-off-by Markus Niebel<[email protected]>--- drivers/input/touchscreen/ads7846.c | 9 ++++----- 1 files changed, 4 insertions(+), 5 deletions(-)drivers/input/touchscreen/ads7846.c +1
-1@@ -1001,15 +1001,14 @@ static void __devinit ads7846_setup_spi_msg(struct ads7846 *ts,struct ads7846_packet *packet = ts->packet;int vref = pdata->keep_vref_on; -if (ts->model ==7873 ) { +if (ts->model ==7873 )/*
drivers/input/touchscreen/ads7846.c static void __devinit ads7846_setup_spi_msg(struct ads7846 *ts, · line 1012
Quoted 10 lines
drivers/input/touchscreen/ads7846.c +3
-4* The AD7873 is almost identical to the ADS7846 -* keep VREF off during differential/ratiometric -* conversion modes. +* set VREF off during differential/ratiometric +* conversion modes if keep_vref_on is not set. +* TODO: does keep_vref_on collide with usage of external vref? */ ts->model =7846 ; - vref =0 ; - }
I would scrap this section from ads7846_setup_spi_msg() completely and force ts->model to 7846 in ads7846_probe() when 7873 is specified.
Quoted 6 lines
drivers/input/touchscreen/ads7846.c +0
-1ts->msg_count =1 ;spi_message_init (m); --1.7.0.4
Signature · 8 lines
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