[PATCH] iio: chemical: bme680: Fix measurement wait duration calculation

[PATCH] iio: chemical: bme680: Fix measurement wait duration calculation

[Chris Spencer]

This function refers to the Bosch BME680 API as the source of the
calculation, but one of the constants does not match the Bosch
implementation. This appears to be a simple transposition of two digits,
resulting in a wait time that is too short. This can cause the following
'device measurement cycle incomplete' check to occasionally fail.

Fixes: 4241665e6ea0 ("iio: chemical: bme680: Fix sensor data read operation")
Link: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/bme68x.c#L521
Signed-off-by: Chris Spencer <spencercw@gmail.com>
---
 drivers/iio/chemical/bme680_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
index 70f81c4a96ba..24e0b59e2fdf 100644
--- a/drivers/iio/chemical/bme680_core.c
+++ b/drivers/iio/chemical/bme680_core.c
@@ -613,7 +613,7 @@ static int bme680_wait_for_eoc(struct bme680_data *data)
 	 * + heater duration
 	 */
 	int wait_eoc_us = ((data->oversampling_temp + data->oversampling_press +
-			   data->oversampling_humid) * 1936) + (477 * 4) +
+			   data->oversampling_humid) * 1963) + (477 * 4) +
 			   (477 * 5) + 1000 + (data->heater_dur * 1000);
 
 	fsleep(wait_eoc_us);
-- 
2.43.0

Re: [PATCH] iio: chemical: bme680: Fix measurement wait duration calculation

[Vasileios Amoiridis]

On Mon, Feb 02, 2026 at 07:38:42AM +0000, Chris Spencer wrote:
> This function refers to the Bosch BME680 API as the source of the
> calculation, but one of the constants does not match the Bosch
> implementation. This appears to be a simple transposition of two digits,
> resulting in a wait time that is too short. This can cause the following
> 'device measurement cycle incomplete' check to occasionally fail.
> 

Hi Chris,

This is a good catch! I didn't have problems with measurements in the
past but that is also because of the entropy of the sensor plus there
were some series with "buggy" sensors that were behaving a bit
differently. In any case, thanks for finding this!

Here is my tag, in case it is of any worth:

Acked-by: Vasileios Amoiridis <vassilisamir@gmail.com>

Cheers,
Vasilis

> Fixes: 4241665e6ea0 ("iio: chemical: bme680: Fix sensor data read operation")
> Link: https://github.com/boschsensortec/BME68x_SensorAPI/blob/v4.4.8/bme68x.c#L521
> Signed-off-by: Chris Spencer <spencercw@gmail.com>
> ---
>  drivers/iio/chemical/bme680_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/chemical/bme680_core.c b/drivers/iio/chemical/bme680_core.c
> index 70f81c4a96ba..24e0b59e2fdf 100644
> --- a/drivers/iio/chemical/bme680_core.c
> +++ b/drivers/iio/chemical/bme680_core.c
> @@ -613,7 +613,7 @@ static int bme680_wait_for_eoc(struct bme680_data *data)
>  	 * + heater duration
>  	 */
>  	int wait_eoc_us = ((data->oversampling_temp + data->oversampling_press +
> -			   data->oversampling_humid) * 1936) + (477 * 4) +
> +			   data->oversampling_humid) * 1963) + (477 * 4) +
>  			   (477 * 5) + 1000 + (data->heater_dur * 1000);
>  
>  	fsleep(wait_eoc_us);
> -- 
> 2.43.0
>