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SubjectRE: [PATCH v5] iio: adc: add new lp8788 adc driver
Date
> Hi,
>
> One issue and a couple of nitpicks inline.

I really appreciate it.
Please see my questions below.

> > + switch (mask) {
> > + case IIO_CHAN_INFO_RAW:
> > + ret = lp8788_get_adc_result(adc, id, val) ? -EIO :
> IIO_VAL_INT;
> > + break;
> > + case IIO_CHAN_INFO_SCALE:
> > + *val = (lp8788_scale[id] / 1000) * 1000;
> > + *val2 = (lp8788_scale[id] % 1000) * 1000000;
>
> This looks suspicious. E.g. if the entry in your table has the value
> "1234"
> you'd end up with a scale factor of 1000.234000000. Which looks wrong
> for
> two reasons, given that you return INT_PLUS_MICRO val2 should never
> exceed 6
> decimal digits and secondly val is multiplied by a factor of thousand.
>
> Can you tell us in what unit the values in lp8788_scale are, that would
> make
> review easier.

The LP8788 has 13 ADC input selection.

ADC selection:
Battery voltage, general ADC1 and so on.

ADC result:
Result = MAX_VALUE * (raw + 0.5) / 4095 except ADC is the charger voltage
If the ADC input is the charger voltage,
Result = MAX_VALUE * (raw + 0.5) / (4095 * 0.48)

The raw value is from the registers.
It has the range between 0 to 4095. (12bits)

MAX_VALUE is constant for each selection.
For the battery voltage, there are three ADC inputs. 5.0/5.5/6.0V
Battery voltage for Max 5.0V = 5.0
Battery voltage for Max 5.5V = 5.5
Battery voltage for Max 6.0V = 6.0
Charger = 6.0
ADC1 = 2.5

I'm afraid I still misunderstand how IIO ADC works.
Could you me some guide how to setup the scale in the driver?

Thank you.

Best Regards,
Milo


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