| Message ID | 20180913073920.16089-1-alexandru.ardelean@analog.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | staging:iio:ad7606: fix voltage scales | expand |
On Thu, 2018-09-13 at 10:39 +0300, Alexandru Ardelean wrote: > Fixes commit 17be2a2905a6ec9aa27cd59521495e2f490d2af0 ("staging: iio: > ad7606: replace range/range_available with corresponding scale"). > > The AD7606 devices don't have a 2.5V voltage range, they have 5V & 10V > voltage range, which is selectable via the `gpio_range` descriptor. > > The scales also seem to have been miscomputed, because when they were > applied to the raw values, the results differ from the expected values. > After checking the ADC transfer function in the datasheet, these were > re-computed. > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com> > --- > drivers/staging/iio/adc/ad7606.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/staging/iio/adc/ad7606.c > b/drivers/staging/iio/adc/ad7606.c > index c5fe3003075b..8f0eebf7316d 100644 > --- a/drivers/staging/iio/adc/ad7606.c > +++ b/drivers/staging/iio/adc/ad7606.c > @@ -26,9 +26,11 @@ > > #include "ad7606.h" > > -/* Scales are computed as 2.5/2**16 and 5/2**16 respectively */ > +/* Scales are computed as 5000/2**16 and 10000/2**16 respectively, Will send a V2. My computation of 32768 [which is mentioned in the datasheet] is also wrong. So, this comment is wrong. > + * so that when applied to the raw values they provide mV values > + */ > static const unsigned int scale_avail[2][2] = { > - {0, 38147}, {0, 76294} > + {0, 152588}, {0, 305176} > }; > > static int ad7606_reset(struct ad7606_state *st)
diff --git a/drivers/staging/iio/adc/ad7606.c b/drivers/staging/iio/adc/ad7606.c index c5fe3003075b..8f0eebf7316d 100644 --- a/drivers/staging/iio/adc/ad7606.c +++ b/drivers/staging/iio/adc/ad7606.c @@ -26,9 +26,11 @@ #include "ad7606.h" -/* Scales are computed as 2.5/2**16 and 5/2**16 respectively */ +/* Scales are computed as 5000/2**16 and 10000/2**16 respectively, + * so that when applied to the raw values they provide mV values + */ static const unsigned int scale_avail[2][2] = { - {0, 38147}, {0, 76294} + {0, 152588}, {0, 305176} }; static int ad7606_reset(struct ad7606_state *st)
Fixes commit 17be2a2905a6ec9aa27cd59521495e2f490d2af0 ("staging: iio: ad7606: replace range/range_available with corresponding scale"). The AD7606 devices don't have a 2.5V voltage range, they have 5V & 10V voltage range, which is selectable via the `gpio_range` descriptor. The scales also seem to have been miscomputed, because when they were applied to the raw values, the results differ from the expected values. After checking the ADC transfer function in the datasheet, these were re-computed. Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com> --- drivers/staging/iio/adc/ad7606.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)