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: <[email protected]>
Signed-off-by: Paul Cercueil <[email protected]>
---
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)
--
2.28.0
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: <[email protected]>
> Signed-off-by: Paul Cercueil <[email protected]>
> ---
> 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 <[email protected]>
Hi Artur,
Le mer. 4 nov. 2020 ? 23:29, Artur Rojek <[email protected]> a
?crit :
> 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: <[email protected]>
>> Signed-off-by: Paul Cercueil <[email protected]>
>> ---
>> 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 <[email protected]>
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 <[email protected]> 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: <[email protected]>
>>> Signed-off-by: Paul Cercueil <[email protected]>
>>> ---
>>> 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 <[email protected]>
>
> 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 <[email protected]> wrote:
> On 2020-11-05 01:09, Paul Cercueil wrote:
> > Hi Artur,
> >
> > Le mer. 4 nov. 2020 à 23:29, Artur Rojek <[email protected]> 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: <[email protected]>
> >>> Signed-off-by: Paul Cercueil <[email protected]>
> >>> ---
> >>> 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 <[email protected]>
> >
> > 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