The rtcfifo module uses RTC memory to store sensor samples across deep-sleeps,
making it possible to batch up samples for less frequent uploads. This
component uses 9 RTC memory slots for control, and a variable number of
slots for sample storage (see rtcfifo.prepare() on how to control the
size/location of the latter).
When used together with the rtctime module, it also exposes the convenience
function rtcfifo.dsleep_until_sample() which can be used to easily take
readings on a regular basis without having to manually take into account
time spent awake to get an accurate sleep time.
The format used for storing samples is quite dense, and allows for 16 bits
of data in a fixed point format (per sample).
Added Lua module rtctime to interface with it.
This keeps as accurate time as is possible on the ESP8266, including across
deep sleeps (provided rtctime.dsleep() is used rather than node.dsleep()).
Intended to be used together with NTP for high accuracy time keeping. The
API is via rtctime.{get,set}timeofday(), working from Unix epoch.
Note that 160MHz CPU clock is not currently supported by the rtctime code,
as it is only aware of the 52MHz boot clock and the regular 80Mhz default
clock.
See rtctime.h for detailed info on how this all works.
Johny Mattsson