Page 212 - Making PIC Microcontroller Instruments and Controllers

CREATING ACCURATE INTERVALS

WITH TIMERS: THE METRONOMES

This chapter is about learnjng to use the timers in a PIC.
First a note about the timer functions and availability. Though there are four timers in
the PIC 16F877A, not all the timers are available lor our projects, rcr are they available
at all times. The other uses for which a timer may be employed are:

a Used with the HPWM instruction
I Used for conmunications
I Control ofthe slave port
I Baud rate generatioo
I Resources are shared with a watchdog timer (Watchdog timer [timer #4] is not
available for any programming purposes but does share scaling resources with
Timer2.)

GETTII{G COMFORTABLE

Ow goal is to be comfortable using the three timers after we have oeated the metronomes
for this poject. All the metronomes created in softwarc and hardware behave identi,
cally but use djfferent timers.
The metronome prcject is essentially a software project in rhat it is about leaming
how to use the timers. We should already have the two pieces of hardware needed to
run the metronome software. They are, of course, the LAB-XI and the board we made
for the last prcject. the tachomerer (to which we will have to add connection points lbr
a potentiometer and a speaker [or LED]). The existing piezo beeper on the LAB X I may
also be used.
Figure 16.2 show that back ol fhe metronome board shown h Figure 16-1.