Cool, I'm happy to try and test some of this out
Setup:
- using UNO R3 for this test - easier for me to flash fuses etc than the Moetino
- Moteino default fuses flashed to UNO before starting
- Measurement functions in the oscilloscope were used to determine the "wake-up" times I've quoted
- Wake-up time is defined as per the above test; Time from external interrupt to asserting a port pin
Start settings, Ext Osc, 8MHz-, 258 CK PowerDown start delay.
Wakeup time of
156.0uS. Good - pretty close to what I saw with the Moteino hardware.
BOD disabled in fuses:
156.0uS. No change!
Internal Osc 8MHz:
208.0uS. Increased!
I tried quite a few different fuse combinations, but did not find anything that gave a faster time than the default Moteino fuse settings. The longer PWRDWN Start Delay options in the clock fuses had a big negative impact of course -
1.160mS with the
Ext Crystal Osc 8.0- MHz; 16K CK option. Actually I think this may be the default setting on some of my clones.
Int RC Osc 128kHz;
9.920 mSI have not looked inside the LowPower library yet. And now my UNO is non-responsive after an unfortunate clock source fuse setting
I will attempt to recover it tomorrow.
Any comments/suggestions or tests you'd like to see performed are more than welcome.
Is it better to abandon the abstractions of the LowPower library and the Arduino IDE for better investigation of PWRDWN -> WAKE timings?