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.

; 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 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