I'm trying to figure out what all I can turn off on a 328P to save on battery consumption. The majority of what it's doing is driving two LED strings (2-wire communication) using A0 - A3 (don't ask), then it has 2 separate LEDs (pins 3 and 4) that act as indicators, one's a heartbeat and the other flashes when the unit receives an RF signal. The RF module uses pins 13, 12, 11, 8, and 7 (SPI communications). The SPI pins are broken out but they're shared with the RF module pins. The FTDI pins are also broken out (RX/TX/RST), and there's an external oscillator attached as well.
So what can be turned off? Do I need the watchdog? Do I need the ADC? What about the timers? And how does one turn them off? Is it all done in programming?