; beep.asm

; load a counter, decrement it, toggle the line and start over

; This program simply drives a piezo element connected between PB0 and Ground.

; You may try connecting between PB0 and Vcc to get more drive.

; Try a Murata PKM13EPY-4000 piezo.  It makes a great annoyance device.

; Play around with the delay tone constant to see what works best.

; I believe that the bit toggle routine illustrates an efficient algorithm

; using the AVR instruction set.

; 

; Written by Brian Hammill 5/98

; This code is given as is and placed in the public domain.  No warranty of any kind

; is implied or given.  Questions or comments about the code may be directed

; to me via Email: hammill@email.exide.com.  I don't promise to support this

; code, but will offer suggestions as my schedule allows.  Good luck. 





.INCLUDE "1200def.INC"

RESET:

	SBI DDRB, 0

BEEP:

	

; set up port B, 0 as an output.  We have piezo buzzer connected to PB0.

	;SBI DDRB, 0	

	

	LDI R19, 247 ; Beep tone constant.

;This loop takes 3 cycles to execute so the beep tone freq is

; f = XTAL/(3*R19)

; f = 3686400/(3*64) = 19200 Hz

		

BEEP_LOOP1:

	dec R19

	brne BEEP_LOOP1

	

	; toggle the bit after count goes to 0

	SBIS PORTB, 0	; Skip if bit is set

	rjmp set_bit0

	CBI PORTB, 0	; Clear if set

	rjmp BEEP





set_bit0:

	SBI PORTB, 0

	rjmp BEEP



	

	; Check whether bit is set or clear and change to opposite.  Want to generate

	; approximately 4KHz signal on PB0.  Toggle line every 921 machine cycles.

	; 3686400/(230*4) = 4006