I discovered two issues.
First the previous sht15_calc_temp() loop did not iterate through the
temppoints array since the (data->supply_uV > temppoints[i - 1].vdd)
test is always true in this direction.
Also the two-points linear interpolation function was returning biased
values, making the temperature reading inaccurate by a non neglectable
factor. This is adressed using a a proportional factor based linear
interpolation.
Signed-off-by: Jerome Oufella <jerome.oufella@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Jonathan Cameron <jic23@xxxxxxxxx>
Cc: Jonathan Cameron <jic23@xxxxxxxxx>
Cc: Jean Delvare <khali@xxxxxxxxxxxx>
---
drivers/hwmon/sht15.c | 14 +++++++-------
1 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/hwmon/sht15.c b/drivers/hwmon/sht15.c
index 864a371..a6ad93b 100644
--- a/drivers/hwmon/sht15.c
+++ b/drivers/hwmon/sht15.c
@@ -303,15 +303,15 @@ error_ret:
static inline int sht15_calc_temp(struct sht15_data *data)
{
int d1 = 0;
- int i;
+ int i, t;
- for (i = 1; i < ARRAY_SIZE(temppoints); i++)
+ for (i = ARRAY_SIZE(temppoints) - 1; i > 0; i--)
/* Find pointer to interpolate */
- if (data->supply_uV > temppoints[i - 1].vdd) {
- d1 = (data->supply_uV/1000 - temppoints[i - 1].vdd)
- * (temppoints[i].d1 - temppoints[i - 1].d1)
- / (temppoints[i].vdd - temppoints[i - 1].vdd)
- + temppoints[i - 1].d1;
+ if (data->supply_uV >= temppoints[i - 1].vdd) {
+ t = (data->supply_uV - temppoints[i-1].vdd) /
+ ((temppoints[i].vdd - temppoints[i-1].vdd) / 10000);
+
+ d1 = (temppoints[i].d1 * t + (10000 - t) * temppoints[i-1].d1) / 10000;
break;
}
--
1.6.3.3
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