| Message ID | 20201104192843.67187-1-paul@crapouillou.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iio/adc: ingenic: Fix battery VREF for JZ4770 SoC | expand |
Hi Paul, On 2020-11-04 20:28, Paul Cercueil wrote: > The reference voltage for the battery is clearly marked as 1.2V in the > programming manual. With this fixed, the battery channel now returns > correct values. > > Fixes: a515d6488505 ("IIO: Ingenic JZ47xx: Add support for JZ4770 SoC > ADC.") > Cc: <stable@vger.kernel.org> > Signed-off-by: Paul Cercueil <paul@crapouillou.net> > --- > drivers/iio/adc/ingenic-adc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iio/adc/ingenic-adc.c > b/drivers/iio/adc/ingenic-adc.c > index ecaff6a9b716..19b95905a45c 100644 > --- a/drivers/iio/adc/ingenic-adc.c > +++ b/drivers/iio/adc/ingenic-adc.c > @@ -71,7 +71,7 @@ > #define JZ4725B_ADC_BATTERY_HIGH_VREF_BITS 10 > #define JZ4740_ADC_BATTERY_HIGH_VREF (7500 * 0.986) > #define JZ4740_ADC_BATTERY_HIGH_VREF_BITS 12 > -#define JZ4770_ADC_BATTERY_VREF 6600 > +#define JZ4770_ADC_BATTERY_VREF 1200 > #define JZ4770_ADC_BATTERY_VREF_BITS 12 > > #define JZ_ADC_IRQ_AUX BIT(0) I thought we set it to 6600 because GCW Zero was not showing correct battery values at 1200. But if you verified that 1200 works with JZ4770, then: Acked-by: Artur Rojek <contact@artur-rojek.eu>
Hi Artur, Le mer. 4 nov. 2020 à 23:29, Artur Rojek <contact@artur-rojek.eu> a écrit : > Hi Paul, > > On 2020-11-04 20:28, Paul Cercueil wrote: >> The reference voltage for the battery is clearly marked as 1.2V in >> the >> programming manual. With this fixed, the battery channel now returns >> correct values. >> >> Fixes: a515d6488505 ("IIO: Ingenic JZ47xx: Add support for JZ4770 >> SoC ADC.") >> Cc: <stable@vger.kernel.org> >> Signed-off-by: Paul Cercueil <paul@crapouillou.net> >> --- >> drivers/iio/adc/ingenic-adc.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/iio/adc/ingenic-adc.c >> b/drivers/iio/adc/ingenic-adc.c >> index ecaff6a9b716..19b95905a45c 100644 >> --- a/drivers/iio/adc/ingenic-adc.c >> +++ b/drivers/iio/adc/ingenic-adc.c >> @@ -71,7 +71,7 @@ >> #define JZ4725B_ADC_BATTERY_HIGH_VREF_BITS 10 >> #define JZ4740_ADC_BATTERY_HIGH_VREF (7500 * 0.986) >> #define JZ4740_ADC_BATTERY_HIGH_VREF_BITS 12 >> -#define JZ4770_ADC_BATTERY_VREF 6600 >> +#define JZ4770_ADC_BATTERY_VREF 1200 >> #define JZ4770_ADC_BATTERY_VREF_BITS 12 >> >> #define JZ_ADC_IRQ_AUX BIT(0) > > I thought we set it to 6600 because GCW Zero was not showing correct > battery values at 1200. > But if you verified that 1200 works with JZ4770, then: > Acked-by: Artur Rojek <contact@artur-rojek.eu> Yes, IIRC we were trying to figure out the range and settled with [-3.3V,+3.3V] since it would give "plausible" values but which were never quite right. The doc does say that the voltage is (hw_val / 4096) * 1.2V, but also says that the ADC operated with 3.3V power supply, I guess we got confused. We never considered the battery could not be connected directly to the ADC's VBAT pin, so a 1.2V reference didn't make sense at that time. I guess we need to learn about electronics :) It turns out the battery is connected to the VBAT pin with a 1 MOhm resistor, and the VBAT pin is also pulled low with a 332 kOhm resistor. So a fully charged battery with 4.2V reads as (4.2V * 332000) / (1332000) = 1.05V, which totally fits in a [0V,+1.2V] range. With that same 4.2V battery I get a hardware value of about 3584, and (3584 / 4096) * 1.2V == 1.05V, which matches the value computed above. So the battery reading looks accurate this time. Cheers, -Paul
On 2020-11-05 01:09, Paul Cercueil wrote: > Hi Artur, > > Le mer. 4 nov. 2020 à 23:29, Artur Rojek <contact@artur-rojek.eu> a > écrit : >> Hi Paul, >> >> On 2020-11-04 20:28, Paul Cercueil wrote: >>> The reference voltage for the battery is clearly marked as 1.2V in >>> the >>> programming manual. With this fixed, the battery channel now returns >>> correct values. >>> >>> Fixes: a515d6488505 ("IIO: Ingenic JZ47xx: Add support for JZ4770 SoC >>> ADC.") >>> Cc: <stable@vger.kernel.org> >>> Signed-off-by: Paul Cercueil <paul@crapouillou.net> >>> --- >>> drivers/iio/adc/ingenic-adc.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/iio/adc/ingenic-adc.c >>> b/drivers/iio/adc/ingenic-adc.c >>> index ecaff6a9b716..19b95905a45c 100644 >>> --- a/drivers/iio/adc/ingenic-adc.c >>> +++ b/drivers/iio/adc/ingenic-adc.c >>> @@ -71,7 +71,7 @@ >>> #define JZ4725B_ADC_BATTERY_HIGH_VREF_BITS 10 >>> #define JZ4740_ADC_BATTERY_HIGH_VREF (7500 * 0.986) >>> #define JZ4740_ADC_BATTERY_HIGH_VREF_BITS 12 >>> -#define JZ4770_ADC_BATTERY_VREF 6600 >>> +#define JZ4770_ADC_BATTERY_VREF 1200 >>> #define JZ4770_ADC_BATTERY_VREF_BITS 12 >>> >>> #define JZ_ADC_IRQ_AUX BIT(0) >> >> I thought we set it to 6600 because GCW Zero was not showing correct >> battery values at 1200. >> But if you verified that 1200 works with JZ4770, then: >> Acked-by: Artur Rojek <contact@artur-rojek.eu> > > Yes, IIRC we were trying to figure out the range and settled with > [-3.3V,+3.3V] since it would give "plausible" values but which were > never quite right. The doc does say that the voltage is (hw_val / > 4096) * 1.2V, but also says that the ADC operated with 3.3V power > supply, I guess we got confused. We never considered the battery could > not be connected directly to the ADC's VBAT pin, so a 1.2V reference > didn't make sense at that time. I guess we need to learn about > electronics :) Yes we do :) > > It turns out the battery is connected to the VBAT pin with a 1 MOhm > resistor, and the VBAT pin is also pulled low with a 332 kOhm > resistor. So a fully charged battery with 4.2V reads as (4.2V * > 332000) / (1332000) = 1.05V, which totally fits in a [0V,+1.2V] range. > > With that same 4.2V battery I get a hardware value of about 3584, and > (3584 / 4096) * 1.2V == 1.05V, which matches the value computed above. > So the battery reading looks accurate this time. Excellent! Thanks for the detailed explanation. Cheers, Artur > > Cheers, > -Paul
On Thu, 05 Nov 2020 01:27:51 +0100 Artur Rojek <contact@artur-rojek.eu> wrote: > On 2020-11-05 01:09, Paul Cercueil wrote: > > Hi Artur, > > > > Le mer. 4 nov. 2020 à 23:29, Artur Rojek <contact@artur-rojek.eu> a > > écrit : > >> Hi Paul, > >> > >> On 2020-11-04 20:28, Paul Cercueil wrote: > >>> The reference voltage for the battery is clearly marked as 1.2V in > >>> the > >>> programming manual. With this fixed, the battery channel now returns > >>> correct values. > >>> > >>> Fixes: a515d6488505 ("IIO: Ingenic JZ47xx: Add support for JZ4770 SoC > >>> ADC.") > >>> Cc: <stable@vger.kernel.org> > >>> Signed-off-by: Paul Cercueil <paul@crapouillou.net> > >>> --- > >>> drivers/iio/adc/ingenic-adc.c | 2 +- > >>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>> > >>> diff --git a/drivers/iio/adc/ingenic-adc.c > >>> b/drivers/iio/adc/ingenic-adc.c > >>> index ecaff6a9b716..19b95905a45c 100644 > >>> --- a/drivers/iio/adc/ingenic-adc.c > >>> +++ b/drivers/iio/adc/ingenic-adc.c > >>> @@ -71,7 +71,7 @@ > >>> #define JZ4725B_ADC_BATTERY_HIGH_VREF_BITS 10 > >>> #define JZ4740_ADC_BATTERY_HIGH_VREF (7500 * 0.986) > >>> #define JZ4740_ADC_BATTERY_HIGH_VREF_BITS 12 > >>> -#define JZ4770_ADC_BATTERY_VREF 6600 > >>> +#define JZ4770_ADC_BATTERY_VREF 1200 > >>> #define JZ4770_ADC_BATTERY_VREF_BITS 12 > >>> > >>> #define JZ_ADC_IRQ_AUX BIT(0) > >> > >> I thought we set it to 6600 because GCW Zero was not showing correct > >> battery values at 1200. > >> But if you verified that 1200 works with JZ4770, then: > >> Acked-by: Artur Rojek <contact@artur-rojek.eu> > > > > Yes, IIRC we were trying to figure out the range and settled with > > [-3.3V,+3.3V] since it would give "plausible" values but which were > > never quite right. The doc does say that the voltage is (hw_val / > > 4096) * 1.2V, but also says that the ADC operated with 3.3V power > > supply, I guess we got confused. We never considered the battery could > > not be connected directly to the ADC's VBAT pin, so a 1.2V reference > > didn't make sense at that time. I guess we need to learn about > > electronics :) > Yes we do :) > > > > It turns out the battery is connected to the VBAT pin with a 1 MOhm > > resistor, and the VBAT pin is also pulled low with a 332 kOhm > > resistor. So a fully charged battery with 4.2V reads as (4.2V * > > 332000) / (1332000) = 1.05V, which totally fits in a [0V,+1.2V] range. > > > > With that same 4.2V battery I get a hardware value of about 3584, and > > (3584 / 4096) * 1.2V == 1.05V, which matches the value computed above. > > So the battery reading looks accurate this time. > Excellent! Thanks for the detailed explanation. Applied to the fixes-togreg branch of iio.git Thanks, Jonathan > > Cheers, > Artur > > > > Cheers, > > -Paul
diff --git a/drivers/iio/adc/ingenic-adc.c b/drivers/iio/adc/ingenic-adc.c index ecaff6a9b716..19b95905a45c 100644 --- a/drivers/iio/adc/ingenic-adc.c +++ b/drivers/iio/adc/ingenic-adc.c @@ -71,7 +71,7 @@ #define JZ4725B_ADC_BATTERY_HIGH_VREF_BITS 10 #define JZ4740_ADC_BATTERY_HIGH_VREF (7500 * 0.986) #define JZ4740_ADC_BATTERY_HIGH_VREF_BITS 12 -#define JZ4770_ADC_BATTERY_VREF 6600 +#define JZ4770_ADC_BATTERY_VREF 1200 #define JZ4770_ADC_BATTERY_VREF_BITS 12 #define JZ_ADC_IRQ_AUX BIT(0)
The reference voltage for the battery is clearly marked as 1.2V in the programming manual. With this fixed, the battery channel now returns correct values. Fixes: a515d6488505 ("IIO: Ingenic JZ47xx: Add support for JZ4770 SoC ADC.") Cc: <stable@vger.kernel.org> Signed-off-by: Paul Cercueil <paul@crapouillou.net> --- drivers/iio/adc/ingenic-adc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)