From: Andreas Klinger <ak@it-klinger.de>
To: jic23@kernel.org, knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net
Cc: linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/3] iio: adc: hx711: optimize sampling of data
Date: Sat, 7 Sep 2019 12:18:00 +0200 [thread overview]
Message-ID: <20190907101759.kft6xwsqc5lf4acq@arbad> (raw)
Fix bug in sampling function hx711_cycle() when interrupt occures while
PD_SCK is high. If PD_SCK is high for at least 60 us power down mode of
the sensor is entered which in turn leads to a wrong measurement.
Move query of DOUT at the latest point of time which is at the end of
PD_SCK low period.
Signed-off-by: Andreas Klinger <ak@it-klinger.de>
---
drivers/iio/adc/hx711.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c
index 88c7fe15003b..0678964dbd21 100644
--- a/drivers/iio/adc/hx711.c
+++ b/drivers/iio/adc/hx711.c
@@ -101,13 +101,14 @@ struct hx711_data {
static int hx711_cycle(struct hx711_data *hx711_data)
{
int val;
+ unsigned long flags;
/*
* if preempted for more then 60us while PD_SCK is high:
* hx711 is going in reset
* ==> measuring is false
*/
- preempt_disable();
+ local_irq_save(flags);
gpiod_set_value(hx711_data->gpiod_pd_sck, 1);
/*
@@ -117,7 +118,6 @@ static int hx711_cycle(struct hx711_data *hx711_data)
*/
ndelay(hx711_data->data_ready_delay_ns);
- val = gpiod_get_value(hx711_data->gpiod_dout);
/*
* here we are not waiting for 0.2 us as suggested by the datasheet,
* because the oscilloscope showed in a test scenario
@@ -125,7 +125,7 @@ static int hx711_cycle(struct hx711_data *hx711_data)
* and 0.56 us for PD_SCK low on TI Sitara with 800 MHz
*/
gpiod_set_value(hx711_data->gpiod_pd_sck, 0);
- preempt_enable();
+ local_irq_restore(flags);
/*
* make it a square wave for addressing cases with capacitance on
@@ -133,7 +133,8 @@ static int hx711_cycle(struct hx711_data *hx711_data)
*/
ndelay(hx711_data->data_ready_delay_ns);
- return val;
+ /* sample as late as possible */
+ return gpiod_get_value(hx711_data->gpiod_dout);
}
static int hx711_read(struct hx711_data *hx711_data)
--
2.13.3
next reply other threads:[~2019-09-07 10:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-07 10:18 Andreas Klinger [this message]
2019-09-08 13:49 ` [PATCH 1/3] iio: adc: hx711: optimize sampling of data Jonathan Cameron
2019-09-09 12:35 ` Andreas Klinger
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