Met vriendelijke groet / kind regards,
Mike Looijmans
System Expert
TOPIC Embedded Products B.V.
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On 06-03-2023 14:29, Andy Shevchenko wrote:
On Mon, Mar 06, 2023 at 02:13:12PM +0100, Mike Looijmans wrote:
The ADS1100 is a 16-bit ADC (at 8 samples per second).
The ADS1000 is similar, but has a fixed data rate.
...
+ microvolts = regulator_get_voltage(data->reg_vdd);
+ /*
+ * val2 is in 'micro' units, n = val2 / 1000000
+ * result must be millivolts, d = microvolts / 1000
+ * the full-scale value is d/n, corresponds to 2^15,
+ * hence the gain = (d / n) >> 15, factoring out the 1000 and moving the
+ * bitshift so everything fits in 32-bits yields this formula.
+ */
+ gain = ((microvolts + BIT(14)) >> 15) * 1000 / val2;
Perhaps adding MICROVOLT_PER_MILLIVOLT (to units.h) and use it here?
Would that require a separate patch?
I fear that would get feedback like "why not MICROCOULOB_PER_MILLICOULOMB".
If I fill in the equation then that "1000" is actually
MICROVOLT_PER_MICROVOLT_PER_MILLIVOLT, which would evaluate to simply
"MILLIVOLT".
Besides that it's seems like
microvolts = regulator_get_voltage(data->reg_vdd);
gain = DIV_ROUNDUP_CLOSEST(microvolts, BIT(15)) *
MICROVOLT_PER_MILLIVOLT / val2;
Yeah, the DIV_ROUNDUP_CLOSEST is more readable.
+ if (gain <= 0 || gain > 8)
+ return -EINVAL;
As I commented out in the previous discussion (please, give a chance to the
reviewers to answer before issuing a new version of the series) this better
to be
if (gain < BIT(0) || gain > BIT(3))
which will show the nature of power of two implicitly.
+ regval = ffs(gain) - 1;
+ ads1100_set_config_bits(data, ADS1100_PGA_MASK, regval);
Can be unified in one line.
Combining it all, I'd arrive at this code:
gain = DIV_ROUNDUP_CLOSEST(microvolts, BIT(15)) * MILLI / val2;
if (gain < BIT(0) || gain > BIT(3))
return -EINVAL;
ads1100_set_config_bits(data, ADS1100_PGA_MASK, ffs(gain) - 1);
+ return 0;
+}
...
+ return ads1100_set_config_bits(
+ data, ADS1100_DR_MASK,
+ FIELD_PREP(ADS1100_DR_MASK, i));
Wrong indentation.
Please, check all your code for this kind of issues.
I always run it through checkpatch.pl but that didn't report on this
indentation.
A bit of digging in the scripts directory yields "Lindent". Feeding my
file to that indeed changes those lines (and some others too). I'll run
my next patch through that.
--
Mike Looijmans
