The Sleepy::loseSomeTime() code in the Ports library was never tested on a JeeNode Micro. Turns out that only a minor library difference kept it from working (the arduino-tiny library has its own version of millis(), etc):
So now, the JNµ can be put to sleep as well. Here’s the jouleTest sketch I used, tweaked to run on the JNµ as well:
And sure enough, about once every 10 seconds it shows that familiar packet-transmit current consumption:
The blue line is the AC-coupled supply voltage, a 3x AA Eneloop battery pack in this case. It supplies about 3.8V, but when running off a 1000 µF cap, it looks like this continues to work down to 1.8V (well below the RFM12B’s minimum 2.2V specs) – although with only about half the transmit power by then.
This current use fingerprint is almost identical to the ATmega328 running this same code. Not surprising really, since it’s the RFM12B which determines most of the power consumption, not the ATmega vs ATtiny difference.