michaelh/zephyr
1
0
Fork 0
Code Releases Activity

drivers: sensors: ti_hdc20xx: update temperature conversion formula

Browse source 
TI recently released a new version of the HDC2080 datasheet, which
slightly update the temperature conversion formula, with a temperature
offset of -40.5°C instead of -40°C. Adjust the code accordingly.

In addition the datasheet also describes a voltage dependent
compensation of -0.08°C/V above 1.8V, however it's not something easily
doable with the current sensor framework, so just ignore that part.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Aurelien Jarno 2021-07-28 21:50:11 +02:00 • committed by Christopher Friedt
commit 9ecdd78961
1 changed files with 4 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

8
drivers/sensor/ti_hdc20xx/ti_hdc20xx.c
View file

@ -29,7 +29,7 @@ LOG_MODULE_REGISTER(TI_HDC20XX, CONFIG_SENSOR_LOG_LEVEL);
/* Temperature and humidity scale and factors from the datasheet ("Register Maps" section) */
#define TI_HDC20XX_RH_SCALE 100U
#define TI_HDC20XX_TEMP_OFFSET -40U
#define TI_HDC20XX_TEMP_OFFSET -2654208 /* = -40.5 * 2^16 */
#define TI_HDC20XX_TEMP_SCALE 165U
struct ti_hdc20xx_config {
@ -87,9 +87,9 @@ static int ti_hdc20xx_channel_get(const struct device *dev,
/* See datasheet "Register Maps" section for more details on processing sample data. */
switch (chan) {
case SENSOR_CHAN_AMBIENT_TEMP:
/* val = -40 + 165 * sample / 2^16 */
tmp = data->t_sample * TI_HDC20XX_TEMP_SCALE;
val->val1 = TI_HDC20XX_TEMP_OFFSET + (tmp >> 16);
/* val = -40.5 + 165 * sample / 2^16 */
tmp = data->t_sample * TI_HDC20XX_TEMP_SCALE + TI_HDC20XX_TEMP_OFFSET;
val->val1 = tmp >> 16;
/* x * 1000000 / 2^16 = x * 15625 / 2^10 */
val->val2 = ((tmp & 0xFFFF) * 15625U) >> 10;
break;