sw: use fixed point (4 fractional bits) for temperature

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
sw: fix infinite loop on failure to complete temp conversion

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
sw: implement simple thermostat

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>