Appendix K: Pseudocode for Pedometer and Timer

Pedometer's ISR

The program enters this ISR on a negative edge of the IRQ line, and during the bouncing phase it will enter this routine a number of times and each time setting the bounce flag.

Pedometer_ISR

IF (pedometer timer is not enabled)

Enable timer

Clear bounce_occurred flag

IF (state equals idle)

Set state to step_occuring

ELSE

Set state to step_occuring_waiting_for_direction

ENDIF

ELSE

Set bounce_occurred flag

ENDIF

RETURN

Timer's ISR

Once the timer is enabled, the program enters this ISR every 8.2 ms until the timer is disabled which occurs after 205 ms of non-bouncing from the pedometer.

Timer_ISR

IF (bounce_occurred)

reset 205 ms counter

Clear the bounce_occurred flag

ELSE

Add 1 to the 205 ms counter

IF (205 ms counter equals 25)

disable interrupt timer

reset 205 ms counter

IF (state equals step_occurring)

signal compass a new direction is needed

ENDIF

change state to step_occurred_waiting_for_direction

ENDIF

RETURN