So, I went and tested their claims and they were correct, indeed. When running Olimexino-328 at 3.3V using battery connector, power down mode instead of power save mode, and watchdog to wake up the board once per minute, I managed to get power usage down to 0.02mA (0.02 milliamps, 20 microamps).
I also made some observations:
- INA219 sensor is pretty accurate when compared to readings from my multimeter
- However, INA219 sensor can measure current only down to 0.1mA, after that I get 0 or negative readings (could be something related to my code)
- The AVR.Watchdog package of AVR-Ada doesn't really support Arduino/atmega328p, so I had to configure the watchdog manually
- At one point, Olimexino-328 was sleeping really deeply and I had to solder ISP header pins to the board because I wasn't able to program the board via serial port
It is somewhat complex to add good watchdog support for atmega328p and also "trigger an interrupt instead of reset" functionality, so I won't be committing my watchdog code to AVR-Ada repos any time soon. Meanwhile, you can get the code from from my arduino-blog repository, examples/deep-sleep directory.