| Message ID | 20220704172116.195841-4-marcus.folkesson@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | Improve MCP3911 driver | expand |
On Mon, 4 Jul 2022 19:21:10 +0200 Marcus Folkesson <marcus.folkesson@gmail.com> wrote: > The ADC conversion is actually not rail-to-rail but with a factor 1.5. > Make use of this factor when calculating actual voltage. > > Fixes: 3a89b289df5d ("iio: adc: add support for mcp3911") > Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com> > Acked-by: Jonathan Cameron <jic23@kernel.org> ? I doubt I gave a tag (mostly because I don't give tags to patches I'll pick up and give a SoB on. Note that tags have to be given explicitly in full form before you can add them to a patch. If in doubt (people often given handwavey responses) then ask people to give an explicit tag. Jonathan > --- > drivers/iio/adc/mcp3911.c | 17 ++++++++++++----- > 1 file changed, 12 insertions(+), 5 deletions(-) > > diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c > index f8875076ae80..890af7dca62d 100644 > --- a/drivers/iio/adc/mcp3911.c > +++ b/drivers/iio/adc/mcp3911.c > @@ -40,8 +40,8 @@ > #define MCP3911_CHANNEL(x) (MCP3911_REG_CHANNEL0 + x * 3) > #define MCP3911_OFFCAL(x) (MCP3911_REG_OFFCAL_CH0 + x * 6) > > -/* Internal voltage reference in uV */ > -#define MCP3911_INT_VREF_UV 1200000 > +/* Internal voltage reference in mV */ > +#define MCP3911_INT_VREF_MV 1200 > > #define MCP3911_REG_READ(reg, id) ((((reg) << 1) | ((id) << 5) | (1 << 0)) & 0xff) > #define MCP3911_REG_WRITE(reg, id) ((((reg) << 1) | ((id) << 5) | (0 << 0)) & 0xff) > @@ -139,11 +139,18 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev, > > *val = ret / 1000; > } else { > - *val = MCP3911_INT_VREF_UV; > + *val = MCP3911_INT_VREF_MV; > } > > - *val2 = 24; > - ret = IIO_VAL_FRACTIONAL_LOG2; > + /* > + * For 24bit Conversion > + * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5 > + * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5) > + */ > + > + /* val2 = (2^23 * 1.5) */ > + *val2 = 12582912; > + ret = IIO_VAL_FRACTIONAL; > break; > } >
Hi, On Sat, Jul 16, 2022 at 06:18:37PM +0100, Jonathan Cameron wrote: > On Mon, 4 Jul 2022 19:21:10 +0200 > Marcus Folkesson <marcus.folkesson@gmail.com> wrote: > > > The ADC conversion is actually not rail-to-rail but with a factor 1.5. > > Make use of this factor when calculating actual voltage. > > > > Fixes: 3a89b289df5d ("iio: adc: add support for mcp3911") > > Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com> > > Acked-by: Jonathan Cameron <jic23@kernel.org> > ? I doubt I gave a tag (mostly because I don't give tags to patches > I'll pick up and give a SoB on. > > Note that tags have to be given explicitly in full form before you can > add them to a patch. If in doubt (people often given handwavey responses) > then ask people to give an explicit tag. Sorry for that. I will remove the tag. I interpreted your "Otherwise looks good to me." as an acked-by. I will only go for explicit tags forward. Thanks, Marcus Folkesson > > Jonathan
diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c index f8875076ae80..890af7dca62d 100644 --- a/drivers/iio/adc/mcp3911.c +++ b/drivers/iio/adc/mcp3911.c @@ -40,8 +40,8 @@ #define MCP3911_CHANNEL(x) (MCP3911_REG_CHANNEL0 + x * 3) #define MCP3911_OFFCAL(x) (MCP3911_REG_OFFCAL_CH0 + x * 6) -/* Internal voltage reference in uV */ -#define MCP3911_INT_VREF_UV 1200000 +/* Internal voltage reference in mV */ +#define MCP3911_INT_VREF_MV 1200 #define MCP3911_REG_READ(reg, id) ((((reg) << 1) | ((id) << 5) | (1 << 0)) & 0xff) #define MCP3911_REG_WRITE(reg, id) ((((reg) << 1) | ((id) << 5) | (0 << 0)) & 0xff) @@ -139,11 +139,18 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev, *val = ret / 1000; } else { - *val = MCP3911_INT_VREF_UV; + *val = MCP3911_INT_VREF_MV; } - *val2 = 24; - ret = IIO_VAL_FRACTIONAL_LOG2; + /* + * For 24bit Conversion + * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5 + * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5) + */ + + /* val2 = (2^23 * 1.5) */ + *val2 = 12582912; + ret = IIO_VAL_FRACTIONAL; break; }
The ADC conversion is actually not rail-to-rail but with a factor 1.5. Make use of this factor when calculating actual voltage. Fixes: 3a89b289df5d ("iio: adc: add support for mcp3911") Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com> Acked-by: Jonathan Cameron <jic23@kernel.org> --- drivers/iio/adc/mcp3911.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-)