| Message ID | 1523637411-8531-11-git-send-email-hernan@vanguardiasur.com.ar (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, 13 Apr 2018 13:36:47 -0300 Hernán Gonzalez <hernan@vanguardiasur.com.ar> wrote: > Add comments to clarify some of the calculations made, specially when > reading or writing values. > Mostly good, but a few minor comments. Jonathan > Signed-off-by: Hernán Gonzalez <hernan@vanguardiasur.com.ar> > --- > drivers/staging/iio/cdc/ad7746.c | 32 +++++++++++++++++++++++++++----- > 1 file changed, 27 insertions(+), 5 deletions(-) > > diff --git a/drivers/staging/iio/cdc/ad7746.c b/drivers/staging/iio/cdc/ad7746.c > index 05506bf9..ef0ebb5 100644 > --- a/drivers/staging/iio/cdc/ad7746.c > +++ b/drivers/staging/iio/cdc/ad7746.c > @@ -429,6 +429,7 @@ static int ad7746_write_raw(struct iio_dev *indio_dev, > goto out; > } > > + /* 2^16 in micro */ I'm not seeing the connection... what is 2^16? > val = (val2 * 1024) / 15625; > > switch (chan->type) { > @@ -554,6 +555,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, > if (ret < 0) > goto out; > > + /* > + * Either for Capacitance, Voltage or Temperature, > + * the 0x000000 code represents negative full scale, > + * the 0x800000 code represents zero scale, and > + * the 0xFFFFFF code represents positive full scale. > + */ > + > *val = (be32_to_cpu(chip->data.d32) & 0xFFFFFF) - 0x800000; > > switch (chan->type) { > @@ -565,7 +573,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, > *val = (*val * 125) / 256; > break; > case IIO_VOLTAGE: > - if (chan->channel == 1) /* supply_raw*/ > + > + /* > + * The voltage from the VDD pin is internally > + * attenuated by 6. > + */ > + > + if (chan->channel == 1) /* supply_raw */ > *val = *val * 6; > break; > default: > @@ -606,6 +620,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, > ret = IIO_VAL_INT; > break; > case IIO_CHAN_INFO_OFFSET: > + > + /* > + * CAPDAC Scale = 21pF_typ / 127 > + * CIN Scale = 8.192pF / 2^24 > + * Offset Scale = CAPDAC Scale / CIN Scale = 338646 > + */ I don't think the following blank line does much other than make it less clear what the comment is about. Same in other locations. Allow the absence of a blank line on one side of the comment to indicate it's association. > + > *val = AD7746_CAPDAC_DACP(chip->capdac[chan->channel] > [chan->differential]) * 338646; > > @@ -614,13 +635,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, > case IIO_CHAN_INFO_SCALE: > switch (chan->type) { > case IIO_CAPACITANCE: > - /* 8.192pf / 2^24 */ > + /* CIN Scale: 8.192pf / 2^24 */ > *val = 0; > *val2 = 488; > ret = IIO_VAL_INT_PLUS_NANO; > break; > case IIO_VOLTAGE: > - /* 1170mV / 2^23 */ > + /* VIN Scale: 1170mV / 2^23 */ > *val = 1170; > *val2 = 23; > ret = IIO_VAL_FRACTIONAL_LOG2; > @@ -674,7 +695,8 @@ static struct ad7746_platform_data *ad7746_parse_dt(struct device *dev) > unsigned int tmp; > int ret; > > - /* The default excitation outputs are not inverted, it should be stated > + /* > + * The default excitation outputs are not inverted, it should be stated > * in the dt if needed. > */ > > @@ -685,7 +707,7 @@ static struct ad7746_platform_data *ad7746_parse_dt(struct device *dev) > ret = of_property_read_u32(np, "adi,exclvl", &tmp); > if (ret || tmp > 3) { > dev_warn(dev, "Wrong exclvl value, using default\n"); > - pdata->exclvl = 3; /* default value */ > + pdata->exclvl = 3; > } else { > pdata->exclvl = tmp; > } -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/staging/iio/cdc/ad7746.c b/drivers/staging/iio/cdc/ad7746.c index 05506bf9..ef0ebb5 100644 --- a/drivers/staging/iio/cdc/ad7746.c +++ b/drivers/staging/iio/cdc/ad7746.c @@ -429,6 +429,7 @@ static int ad7746_write_raw(struct iio_dev *indio_dev, goto out; } + /* 2^16 in micro */ val = (val2 * 1024) / 15625; switch (chan->type) { @@ -554,6 +555,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, if (ret < 0) goto out; + /* + * Either for Capacitance, Voltage or Temperature, + * the 0x000000 code represents negative full scale, + * the 0x800000 code represents zero scale, and + * the 0xFFFFFF code represents positive full scale. + */ + *val = (be32_to_cpu(chip->data.d32) & 0xFFFFFF) - 0x800000; switch (chan->type) { @@ -565,7 +573,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, *val = (*val * 125) / 256; break; case IIO_VOLTAGE: - if (chan->channel == 1) /* supply_raw*/ + + /* + * The voltage from the VDD pin is internally + * attenuated by 6. + */ + + if (chan->channel == 1) /* supply_raw */ *val = *val * 6; break; default: @@ -606,6 +620,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, ret = IIO_VAL_INT; break; case IIO_CHAN_INFO_OFFSET: + + /* + * CAPDAC Scale = 21pF_typ / 127 + * CIN Scale = 8.192pF / 2^24 + * Offset Scale = CAPDAC Scale / CIN Scale = 338646 + */ + *val = AD7746_CAPDAC_DACP(chip->capdac[chan->channel] [chan->differential]) * 338646; @@ -614,13 +635,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, case IIO_CHAN_INFO_SCALE: switch (chan->type) { case IIO_CAPACITANCE: - /* 8.192pf / 2^24 */ + /* CIN Scale: 8.192pf / 2^24 */ *val = 0; *val2 = 488; ret = IIO_VAL_INT_PLUS_NANO; break; case IIO_VOLTAGE: - /* 1170mV / 2^23 */ + /* VIN Scale: 1170mV / 2^23 */ *val = 1170; *val2 = 23; ret = IIO_VAL_FRACTIONAL_LOG2; @@ -674,7 +695,8 @@ static struct ad7746_platform_data *ad7746_parse_dt(struct device *dev) unsigned int tmp; int ret; - /* The default excitation outputs are not inverted, it should be stated + /* + * The default excitation outputs are not inverted, it should be stated * in the dt if needed. */ @@ -685,7 +707,7 @@ static struct ad7746_platform_data *ad7746_parse_dt(struct device *dev) ret = of_property_read_u32(np, "adi,exclvl", &tmp); if (ret || tmp > 3) { dev_warn(dev, "Wrong exclvl value, using default\n"); - pdata->exclvl = 3; /* default value */ + pdata->exclvl = 3; } else { pdata->exclvl = tmp; }
Add comments to clarify some of the calculations made, specially when reading or writing values. Signed-off-by: Hernán Gonzalez <hernan@vanguardiasur.com.ar> --- drivers/staging/iio/cdc/ad7746.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-)