In order to see the effects of the power optimizations, we must exclude the electronics that are not related to the system. Our reference board, for example, the STM32F407-Discovery, has an additional microcontroller that is used to provide a debug interface towards the host, and it is powered using the same USB connector. However, development kits often offer a way to measure the current excluding the unrelated hardware, allowing to properly evaluate the low-power features of the microcontroller, excluding the development-related circuitry on board.
On our reference board, the jumper JP1 can be used to open the circuit between the power supply and the microcontroller circuitry. Replacing the jumper with an ammeter connected ...
