DocID026482 Rev 1

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AN4515

Application note use case

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2.3

Functional description

The principle of this use case is summarized in the state machine shown in Figure 12.

Figure 12. Use case state machine

The main steps of the application use case are the following:

1.

The master and the sensor are powered on. By default the system is in STDBY state

(Standby mode).

2.

The user starts running the application by pushing the user button (PA0 on

32F401CDISCOVERY board).The CPU goes to SLEEP1 state while a DMA transfers

startup message is displayed via USART2 and USB virtual comport.

3.

When DMA transfers are complete, the CPU wakes up from SLEEP1 and enters STOP

waiting for the user to read the configuration menu below (see Figure 13):

1: Flash active while CPU in sleep: Flash memory is running

2: Stop Flash while CPU in sleep: this configuration brings out the BAM feature.

3: Enable Time Stamp and Flash active while CPU in sleep: this option is used to

track the different application state consumptions with using the period of each state

displayed in timestamp log.

4: Enable Time Stamp and stop Flash while CPU in sleep: this option allows

benefiting both from the second and third configurations.