On Sat, Nov 20, 2021 at 09:28:56PM +0000, David Mosberger-Tang wrote:
> Per datasheet, SHT4x may need up to 8.2ms for a "high repeatability"
> measurement to complete. Attempting to read the result too early
> triggers a NAK which then causes an EREMOTEIO error.
>
> This behavior has been confirmed with a logic analyzer while running
> the I2C bus at only 40kHz. The low frequency precludes any
> signal-integrity issues, which was also confirmed by the absence of
> any CRC8 errors. In this configuration, a NAK occurred on any read
> that followed the measurement command within less than 8.2ms.
>
> Signed-off-by: David Mosberger-Tang <davidm@xxxxxxxxxx>
Applied.
Thanks,
Guenter
> ---
> drivers/hwmon/sht4x.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c
> index 09c2a0b06444..3415d7a0e0fc 100644
> --- a/drivers/hwmon/sht4x.c
> +++ b/drivers/hwmon/sht4x.c
> @@ -23,7 +23,7 @@
> /*
> * I2C command delays (in microseconds)
> */
> -#define SHT4X_MEAS_DELAY 1000
> +#define SHT4X_MEAS_DELAY_HPM 8200 /* see t_MEAS,h in datasheet */
> #define SHT4X_DELAY_EXTRA 10000
>
> /*
> @@ -90,7 +90,7 @@ static int sht4x_read_values(struct sht4x_data *data)
> if (ret < 0)
> goto unlock;
>
> - usleep_range(SHT4X_MEAS_DELAY, SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
> + usleep_range(SHT4X_MEAS_DELAY_HPM, SHT4X_MEAS_DELAY_HPM + SHT4X_DELAY_EXTRA);
>
> ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
> if (ret != SHT4X_RESPONSE_LENGTH) {
