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drivers: sensor: ccs811: Fix value conversion

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The arithmetic performed on the CO2 and VOC measurements is pointless as
the units of the sensor already match those of the API, furthermore the
multiplication will overflow the u32_t with CO2 or VOC readings greater
than 4294 ppm or ppb. This CO2 concentration is achievable by breathing
at the sensor.

Signed-off-by: Aapo Vienamo <aapo.vienamo@iki.fi>
This commit is contained in:
Aapo Vienamo 2018-02-24 16:25:56 +02:00 • committed by Kumar Gala
commit 0a6f8c1aa2
1 changed files with 5 additions and 8 deletions
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13
drivers/sensor/ccs811/ccs811.c
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@ -66,21 +66,18 @@ static int ccs811_channel_get(struct device *dev,
switch (chan) {
case SENSOR_CHAN_CO2:
uval = drv_data->co2 * 1000000;
val->val1 = uval / 1000000;
val->val2 = uval % 1000000;
val->val1 = drv_data->co2;
val->val2 = 0;
break;
case SENSOR_CHAN_VOC:
uval = drv_data->voc * 1000000;
val->val1 = uval / 1000000;
val->val2 = uval % 1000000;
val->val1 = drv_data->voc;
val->val2 = 0;
break;
case SENSOR_CHAN_VOLTAGE:
/*
* Voltage readings are contained in least
* significant 10 bits in volts
* Raw ADC readings are contained in least significant 10 bits
*/
uval = (drv_data->resistance & CCS811_VOLTAGE_MASK)
* CCS811_VOLTAGE_SCALE;