steven niu / Mbed 2 deprecated LP1768-lowpower_test

a test code to implement and test LP1768 power control mode

Dependencies:   mbed

This code implemented some LP1768 power mode : Sleep(), DeepSleep(), PowerDown(), DeepPowerDown(), BOGD_PowerDown(). It also has a test code to test these power modes and wakeup using watch dog. The wakeup part is based on Erik's code but add implementation for LP1768. As LP1768 has debug enabled in default, it cannot be waked up in DeepSleep mode. Therefore this code use WDC reset to wake up the chips from deep sleep. The test code also allow test the power under two clock frequency (96 MHz and 48MHz). Inspired by Paul and Michael Wang, I also tested the power reduction by power off PHY. The analysis could be found in http://mbed.org/users/steniu01/notebook/lp1768-power-mode-implementation-and-measurement-/#