Fake Cricket

A fake cricket is not a really useful application, but it is very simple to create and can be fun to drive people crazy. Or to hide and seek with children.

If you use a high-impedance speaker, it can be driven directly from the output pins of your microcontroller. A piezo element should also work, but might not give much output power with low voltages.

For a low-impedance speaker a simple 'amplifier' (transistor) should work.

Tip: Instead of connecting your output speaker with one pin to VDD/VSS, more output can be generated by connecting with two output pins and swapping them. This trick seems to work, and I think it works because a speaker is current-driven. For a piezo, it doesn't matter, since a piezo is voltage-driven.

Cricket sample code:

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File cricket.asm

Assembly code for a 4MHz PIC12F509 microcontroller

Description

Fake cricket sound for a 12F509

Author

Vincent

Last Modified

17 / 8 / 06

CPU configuration

       processor 12f509
        __config  _IntRC_OSC & _WDT_OFF & _MCLRE_OFF

=======================================

Configuration (FUSE) BIT Definitions

=======================================

_MCLRE_ON EQU 0FFFh _MCLRE_OFF EQU 0FEFh _CP_ON EQU 0FF7h _CP_OFF EQU 0FFFh _WDT_ON EQU 0FFFh _WDT_OFF EQU 0FFBh _LP_OSC EQU 0FFCh _XT_OSC EQU 0FFDh _IntRC_OSC EQU 0FFEh _ExtRC_OSC EQU 0FFFh

509 defs

PCL equ H'02' STATUS equ H'03' OSCCAL equ H'05' GPIO equ H'06' Z equ H'02'

variables

CounterA equ H'1F' ; delay counter CounterB equ H'1E' ; delay counter CounterC equ H'1D' ; delay counter CounterD equ H'1C' ; delay counter

statics

aupin equ H'00' aupin2 equ H'01'

Program

       org     0         	; start at address 0
       

start: movwf OSCCAL ; calibration bits movlw 0 ; set tris read except for aupin tris GPIO

mainloop:

call freq4500 call freq4200 call freq4500 call freq4200 call freq4500 call freq4200 call freq4500 call freq4200

none: call secdelay

goto mainloop

subs

freq4200: ; freq loop should be 238 cycles to get 4200Hz movlw 0040h ; counter set for 11msec movwf CounterD

loop42: bcf GPIO,aupin bsf GPIO,aupin2 call del42 bcf GPIO,aupin2 bsf GPIO,aupin call del42

decfsz CounterD,1 goto loop42

retlw 0

freq4500: ; freq loop should be 222 cycles to get 4500Hz movlw 002Dh ; counter set for 14msec movwf CounterD loop45: bcf GPIO,aupin bsf GPIO,aupin2 call del45 bcf GPIO,aupin2 bsf GPIO,aupin call del45

decfsz CounterD,1 goto loop45

retlw 0

del42 movlw 0023h movwf CounterA

loop4 decfsz CounterA,1 goto loop4

retlw 0

del45 movlw 0026h movwf CounterA

loop5 decfsz CounterA,1 goto loop5

retlw 0

secdelay

insert picloops code here

PIC Time Delay = 8,0000040 s with Osc = 4,000000 MHz

movlw D'41' movwf CounterC movlw D'190' movwf CounterB movlw D'87' movwf CounterA sloop decfsz CounterA,1 goto sloop decfsz CounterB,1 goto sloop decfsz CounterC,1 goto sloop retlw 0

       end