0.5-5.5V power input to be able to run on many kind of batteries using TPS61201.
2.54mm pinout of GPIO spaced so it will be easy to put the devboard on a breadboard.
Pullup/down resistors attached for boot, deepsleep, chip enable.
Deepsleep output prewired to reset
ADC connected to a voltage divider from the battery.
Version 2: Comment on ideas below :) I want something really small but with a lot of functions and still lowpower, I thinking USB programming and an even smaller board
- USB2serial (Candidate: CP2101)
- Even smaller board (0.1" smaller width to work on my breadboard, as small as possible in length)
- LiPo charging (so you can use your old nokia battery to power your things) (Candidate: https://www.sparkfun.com/products/11231)
- Disconnetable ADC measurement of battery for even lower power when not used. (Candidate: One transistors with capacitor on gate to disconnect the high side to prevent to high voltage on the input compared to low side one transistor)