In progress with a project where we are using K20 100 MHz device (rev1.4), battery powered and connectable via USB to a computer/charger.
We are using WAIT, STOP and Low Leakage STOP for power saving, but when we are connected via USB, we must use WAIT mode to maintain the USB connection. Since this mode draws considerably much more power than any STOP mode, we are investigating ways to idle more efficiently (the operating system is in its 'idle' thread for almost 100% of the time when connected to a host).
We have two external crystals, 32kHz and 16 MHz.
Is there a way to have USB fully functional also in STOP mode, or is there any other preferred way of power saving while USB connected?
Thanks for any pointers in this matter!