@alowhum
All of them from Amazon sold by Amazon, i m out of ideas how and where to get genuine sd cards

may be its time for Raspberry pi foundation to put some storage on the board, these fake cards are very unreliable and i think small pc is better option then Raspberry pi at this stage.

i know this is old thread but here is what i have to deal with, truck load of different sd card ordered from amazon from different supplier, some full filled by amazon and some sold by amazon and all of them are fake and devil is in serial number so until you order more then one SD card you can never know if its real or fake.

any reason this is deleted from Openhardware site?

@avelo
thank you for suggestion, i have made prototype based on MIC5219-3.3
but sure TPS61291 / TPS61221 are good options. once i get pcb delivered i'll you know here.

10pcs/lot MIC5219-3.3BM5 SOT-23 MIC5219-3.3 3.3V MIC5219-3.3YM5 LG33 LDO Regulator

$0.79

@bjacobse
reason behind 1mhz mcu is to run it on lower voltage but switching between speed still need higher voltage. if i m not wrong!!!

Life is never easy and definitely not straight, there is always something wrong perhaps back to educating myself...

it would be interesting to see what sleep function does, may be need to read library code to understand this in more detailed.

your work gave me starting point but there is lot to learn/read about this.... thank you for sharing,

further update:
while playing with 1mhz bootloader and feeding arduino to raw pin from 18650 battery, sensors is successfully sending battery voltage and battery percentage but no temperature sensor reading. to prove that something isnt right with 1mhz bootloader i burned 8mhz default bootloader i get battery voltage, battery percentage and temperature reading. can not think of something obvious

Link to 1mhz bootloader