A bit more to add after seeing @apophene’s post “top” and Cayenne do not agree on RPi CPU usage if Android is (or has been) connected. I’ve verified via top that the CPU is maxed out while android is connected.
Returning to normal after I kill the android connection:
In addition it’s maxed out with only android connected and not the web dashboard:
And then frees up, with nothing connected, i.e. android disconnected.
For my testing I’m rebooting the android device, an LG G2, to ensure it’s killed.