Fake Cricket
From Just in Time
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.
Here is the Fake Cricket built in a cheap scan radio.
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 output
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 ; which is in fact 8 secs
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