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drivers: sensors: bmp581: fix temperature scaling #97083

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drivers: sensors: bmp581: fix temperature scaling #97083

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14 changes: 10 additions & 4 deletions drivers/sensor/bosch/bmp581/bmp581.c
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Original file line number Diff line number Diff line change
Expand Up @@ -405,11 +405,17 @@ static int bmp581_sample_fetch(const struct device *dev, enum sensor_channel cha

ret = bmp581_reg_read_rtio(&conf->bus, BMP5_REG_TEMP_DATA_XLSB, data, 6);
if (ret == BMP5_OK) {
/* convert raw sensor data to sensor_value. Shift the decimal part by 1 decimal
* place to compensate for the conversion in sensor_value_to_double()
/* convert raw sensor data to sensor_value.
* BMP581 temperature data is 24-bit signed with LSB = 1/65536 °C
*/
drv->last_sample.temperature.val1 = data[2];
drv->last_sample.temperature.val2 = (data[1] << 8 | data[0]) * 10;
int32_t raw_temp = ((int32_t)((uint32_t)(((uint32_t)data[2] << 16) |
((uint16_t)data[1] << 8) | data[0])
<< 8) >>
8);
Comment on lines +408 to +414
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Instead of shifting 8 up and 8 down, I suggest using sign_extend(), similar to how it's done in the decoder:

zephyr/drivers/sensor/bosch/bmp581/bmp581_decoder.c

Lines 125 to 130 in ca85e76

case SENSOR_CHAN_AMBIENT_TEMP: {
/* Temperature is in data[2:0], data[2] is integer part */
uint32_t raw_temp = ((uint32_t)frame[*fit].payload[2] << 16) |
((uint16_t)frame[*fit].payload[1] << 8) |
frame[*fit].payload[0];
int32_t raw_temp_signed = sign_extend(raw_temp, 23);


/* Convert raw temperature: LSB = 1/65536 °C, val2 in millionths */
drv->last_sample.temperature.val1 = raw_temp / 65536;
drv->last_sample.temperature.val2 = ((int64_t)(raw_temp % 65536) * 1000000) / 65536;

if (drv->osr_odr_press_config.press_en == BMP5_ENABLE) {
/* convert raw sensor data to sensor_value. Shift the decimal part by
Expand Down