From: "Kim, Milo" <Milo.Kim@ti.com>
To: Lars-Peter Clausen <lars@metafoo.de>
Cc: Jonathan Cameron <jic23@kernel.org>,
Jonathan Cameron <jic23@cam.ac.uk>,
"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v5] iio: adc: add new lp8788 adc driver
Date: Fri, 14 Sep 2012 00:33:27 +0000 [thread overview]
Message-ID: <A874F61F95741C4A9BA573A70FE3998F41EF4BFC@DQHE02.ent.ti.com> (raw)
In-Reply-To: <504DADE1.6010303@metafoo.de>
> 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
next prev parent reply other threads:[~2012-09-14 0:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-10 8:02 [PATCH v5] iio: adc: add new lp8788 adc driver Kim, Milo
2012-09-10 9:07 ` Lars-Peter Clausen
2012-09-14 0:33 ` Kim, Milo [this message]
2012-09-14 8:35 ` Lars-Peter Clausen
2012-09-15 0:15 ` Kim, Milo
2012-09-15 9:05 ` Jonathan Cameron
2012-09-13 12:23 ` Jonathan Cameron
2012-09-14 0:33 ` Kim, Milo
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