Thank you for your suggestion and I completely agree to your points westfw.
2. Basically I was targeting at a Buck / Boost regulator. Lets say if I want to run at 12MHz or greater I need a voltage equivalent. I cannot fully use my Lipo for it. I would be overclocking it. If I switch off avr I will loose RTC.
- If I do it on any other board I need to maintain the crystal according to the supply voltage.
4/5 I would be loosing max of 3 pins since for ADC of battery voltage and current I am using additional adc which an available on smd package. I am still having 4 ADC, SPI, I2C, UART enough to make it run. Even the battery adc is started via the avr and the current adc is just a few ua when the external regulator is switched off.
- To avoid losses I am using only internal reference as the vref pin is just decoupled with a capacitor.
Yes AVR are not IOT ready. We may require an external IC's. Just as an example the new coming IC WINC1500 from avr can bring down WiFi in wait mode to 1ma. But if my avr continues to work in active mode taking more than 5ma (again depends on the external use of I/O ports) then it is irrelevant. But the same if I run just for RTC (Power save mode) and use interrupt to wake up it will bring down to 5ua thus giving a battery life as such required. I know ATSAM processor will be best as Arduino Zero would be available soon.