Sanity check: battery powered wireless logger

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Epyon

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I'm tinkering with a new project which is something in the line of a battery powered datalogger with wireless communication (RN2483) and local data storage (SD), but a sanity check before spending too much time on it may be nice :) .

The plan is to use a T3.2 which will be sleeping most of the time, just to be awoken periodically by an external trigger (which just increments a counter) or by the RTC to periodically log the counter to SD and transmit it through the RN2483 radio. The Teensy will be battery powered by 3 alkaline batteries (totaling to 4.8V) and needs to run as long as possible without any human intervention. This brings me to the following questions:

1. duffs Snooze library puts the LDO into a low power state during hibernate. Will the RTC continue to run adequately with the batteries connected to Vin, or will an additional RTC backup battery be required?

2. Will SPI and SDfat resume proper functioning after returning from hibernate?

3. Would there be any benefit of using an external DC-DC converter (4.8V battery to 3.3V) instead of the LDO? Considering the Teensy would be sleeping most of the time and a DC-DC converter also has some idle draw, I would think not?

4. Can Snooze be used to wake the Teensy up on absolute timestamps (e.g. every quarter of the hour sharp hh:00, hh:15 etc)? Judging from the example, it looks like it uses relative intervals (e.g. every 10 minutes).

The RN2483 modem will be put to sleep through UART commands, drawing 40µA at 3.3V when not transmitting.
 
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