Add missing braces to comply with MISRA C:2012 Rule 15.6 and
also following Zephyr's style guideline.
Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>
This style is used in sensor drivers. It's more complicated than the
other way, which is used in different drivers that are not sensor
drivers.
Signed-off-by: Trent Piepho <tpiepho@gmail.com>
The existing code rounded the result to an integer, then multiplied that
integer by 1000000 to get micro-degrees or micro-percent, and then
divided by 1000000 to get whole degrees/percent and took the modulus to
get fractional degrees/percent.
Obviously, multiplying and then dividing an integer by the same value
has no effect!
The result is the humidity and temperature were always rounded down to
the nearest integer.
Fix this to properly keep the fractional component. This is done in a
way that avoids any integer divisions, which are slow on all CPUs, but
especially most microcontrollers, e.g. Cortex-M, lack any integer
division instruction.
Avoiding the base 10 math does not require more code. One just needs to
think in binary and use binary fractions instead of base 10 fractions.
Signed-off-by: Trent Piepho <tpiepho@gmail.com>
The low two bits are not part of the data, but rather "status" bits that
should be masked off.
This is documented in the HTU21D datasheet Edition 8, date 05/2017, pp.
15, and Sensirion SHT21 datasheet version 6, date 10/2022, §6 (wording
exactly the same):
"The two status bits, the last bits of LSB, must be set to ‘0’ before
calculating physical values."
Also Silicon Labs Si7006 example driver code:
/* Swap the bytes and clear the status bits */
return ((data.byte[0] * 256) + data.byte[1]) & ~3;
Since these are the LSBs, it has only a small effect and might not have
been noticed despite being wrong.
While editing this code, switch to using the Zephyr endian conversion
functions intead of a written out conversion.
Add error code to error log message.
Signed-off-by: Trent Piepho <tpiepho@gmail.com>
These three sensor types are all largely compatible. The SHT21 and
HTU21D can be supported by this driver by sending command 0xE3 instead
of 0xE0 to read the temperature.
Mention the sensor names in bindings and Kconfig to help those looking
for support to find it. There have been at least five PRs attempting to
add SHT21 and/or HTU21D support that did not realize the Si7006 is the
same.
As mentioned in PR #22862, the Sensirion SH21 is the original. The dts
bindings are adjusted (in a backward compatible way!) to make the sht21
the base binding and si7006 is derived from that.
Examples of dts compatibles:
TE Connectivity née Measurement Sepcialties HTU21D:
compatible = "meas,htu21d", "sensirion,sht21";
Sensirion SHT21:
compatible = "sensirion,sht21";
Silicon Labs Si7006
compatible = "silabs,si7006";
Silicon Labs Si7021
compatible = "silabs,si7021", "silabs,si7006";
Signed-off-by: Trent Piepho <tpiepho@gmail.com>
