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PIR (PASSIVE INFRARED) DETECTOR USING ST7FLITE05/09/SUPERLITE

Figure 6. Timer ISR (Interrupt Service routine) Flowchart

Does

Counter=Number

of conversions?

(e.g.1000)

Write the first level to be output on PA5 pin according to the data (ASCII)

to be transmitted at selected baud rate

IRET

Is ADC

input signal

> Threshold?

Yes

No

Make Biasing signal LOW and in-

crement low_var, to count the

number of times the signal is

made LOW

Make Biasing

signal HIGH

START

Change the level of the port pin PA5 according to the ASCII data after every

416µs (52x8=8th occurence of timer interrupt) for baud rate 2400 and

208 µs for 4800 baud rate.

Decrement counter

Counter=Number of conversions

Store low_var value in buffer

SCI

Trans-

mission

Sigma-Delta

Implementatio

Yes

No