DocID026505 Rev 1

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AN4538

STM32F3xx microcontroller low-power application example

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2.3.2

Application setup

Once the previous software and hardware recommendations have been followed and the

NUCLEO-F302R8 is ready to use, the user has to proceed as follow:

•

Open a serial port terminal interface in the PC.

•

Connect ST-link cable between NUCLEO-F302R8 and PC to power-on the board.

•

Open the serial port terminal while the device remains in Standby mode.

•

Push the button connected to PA0 to start the application state machine or wait for the

RTC period to elapse.

•

Once the menu message is displayed, select one of the four configuration by pushing

the key and send the right character (1-4).(see note)

•

Ensure that the PWM signal is generated and displayed on the oscilloscope.

•

Turn on the DC power supply and apply a DC voltage that exceeds the reference

the power supply output.

•

Once the message prompting the user that the device will return to standby is

displayed, execute the sequence again by pushing the button or wait for the RTC

period to elapse.

Note:

Depending on the choice done by the user, Voltage reference can be 1.2V (Vrefint) or 2V

(DAC1_OUT1) and the log time can be displayed or not in the last message.

The user has to apply the same sequence of steps described above to get a correct

functionality of the application.

2.4

Application current consumption

The measure of the application's average current consumption is necessary to estimate the

power budget of the application and deduce the battery life for such portable application.

2.4.1

Measuring current consumption

As an example, the average current consumption of the first state machine cycle processing

has been measured by activating the ’Min Max’ mode of the multimeter before powering on

the NUCLEO-F302R8 board. The hold button is pushed just after the first return to Standby

mode.

In this measured case, the Vrefint is selected as the inverting input of the comparator 2 and

the log time display is activated.

The average current is equal to 480 µA.

Before returning to standby, the application displays the log time of different low-power

modes existing in the application state machine. Figure 8 shows the log time displayed for

the first time of the application processing.

Note that the wakeup time of Sleep3 mode is displayed in the second cycle of the state

machine.