AN3260 datasheet(14/24 Pages) STMICROELECTRONICS

14 / 24 page

Software description

AN3260

14/24

Doc ID 17836 Rev 1

4.3.2

Interrupt function flowcharts

Pushbutton acquisition

Each time Button1 or Button2 is pressed, an interrupt is triggered and the

PORTA_IRQhandler() function is called. The PORTA_IRQhandler() routine identifies which

pushbutton has been pressed by testing port A input register and asserts the

ButtonPressed1 or ButtonPressed2 flag accordingly (see Section 4.3.3: State machine

flowchart). These flags trigger a change of state in the application state machine

Figure 5 shows the flowchart of the PORTA_IRQhandler() function.

Figure 5.

PORTA_IRQhandler() function flowchart

Timer-triggered acquisition

TIMER3 is configured to generate an interrupt every 50 ms to trigger temperature

acquisitions.

After each conversion of ADC1 channel 2, the digital value is stored in the buffer array for

further computations and ADC1 is powered down. A maximum of 16 samples are saved in

the buffer array. This allows dividing by a power of two by performing a simple right shift,

when calculating the average temperature over one-second period.

TIM3_IRQHandler() calls the TRtc_CntUpdate() function which simulate a real time clock. It

sets the flags representing seconds, minutes, and hours. This RTC routine is based on TIM3

50 ms timebase. Every second, the state machine automatically switches to state 3 (normal

mode) (see Section 4.3.3: State machine flowchart).

Figure 6 shows the flowchart of the TIM3_IRQhandler() function.

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