- Converting the alert registers and the ambient temp register to a
physic.Temperature can use the same procedure. Unify them and document
why this is possible.
- Use != instead of > for bit checks
- Inline bitsToTemperature calls in SenseWithAlerts
The datasheet (http://ww1.microchip.com/downloads/en/DeviceDoc/25095A.pdf)
says that negative temperatures are stored in two's complement. See
page 22 for alert registers and pages 24-25 for the ambient temperature
register.
However, the code currently assumes negative values are stored in a
sign-and-magnitude representation. Fix this to handle two's complement
values correctly.
For register bits to temperature conversion this implementation follows
the datasheet, but the code in the datasheet isn't quite right -- it
should be `temp - 256` instead of `256 - temp` -- but the fact that the
256 figure is in Microchip's code backs up the idea stated in the text
that negative values are in two's complement. Others seem to agree that
this is correct: https://electronics.stackexchange.com/a/244826
For temperature to bits conversion this implementation relies on the
fact that Go also uses two's complement. I've added a long comment in
the code about this.
Michael Traver