The Silicon Labs Si705x sensors (Si7050/1/3/4/5) are very similar to the
Si7021 sensors featuring only a temperature sensor and no humidity
sensor. The only difference between the Si705x is the temperature
accuracy of the reading, ranging from +/- 0.1 C in the Si7051 to +/- 1 C
in the Si7050.
This patch adds support for this family of sensors extending the
functionality of the existing si70xx driver. Following the style of
other modules, this implements a pseudomodule per supported chip, adding
si7050, si7051, si7053, si7054 and si7055 pseudomodules.
As a minor change this patch also implements the missing
si70xx_get_serial, si70xx_get_id and si70xx_get_revision functions that
were declared in the si70xx.h header but implemented as private
functions. The si70xx_get_id() may be relevant for the application to
know at run time exactly which version of the hardware is installed.
The updated test running with a Si7051 shows the following output, which
seems consistent with the room temperature conditions during the test.
```
make SI70XX_VARIANT=si7051 -C tests/driver_si70xx/ all flash
```
```
SI70XX temperature and humidity sensor test application
Initializing sensor...
[OK]
Found SI7051 sensor, revision 32
temperature: 24.71 C
temperature: 24.69 C
```
tests/driver_ds3231
drivers/ds3231: add alarm support with IRQ
drivers/ds3231: alarm support and documentation
drivers/ds3231: alarm interrupt with mutex
drivers/ds3231: alarm, _unlock function
fixup! drivers/ds3231: add alarm support
Some periph_rtt implementations do not provide `rtt_set_counter()`. This
adds `periph_rtt_set_counter` as feature to allow testing for its
availability. The feature is provided at CPU level if periph_rtt is
provided by the board for all CPUs implementing `rtt_set_counter()`.
The clock adjustment API only used a 16 bit integer for speed correction. This
is to course grained to allow compensating clock drifts at high accuracy.
Using a 32 bit integer instead would allow to fix for a drift of up to
about 1 nanosecond drift per each 5 seconds.
That ought to be enough for anyone! (*cough* *cough*)
- Use negative errno as error codes, rather than home-grown enums
- Update the home-grown enum with negative errno codes for backward
compatibility and mark it deprecated
- Update API doc to use negative errno codes
- Fix various style issues in Doxygen doc
- Use `@retval` to document specific return values instead of abusing
`@return` for this
- Align parameters to proper indent level
