View source for 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 / low frequencies.

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 alternating 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