Generating sound

In microcontroller systems, beeper is used for indicating certain occurrences, such as push of a button or an error. To have the beeper started, it needs to be delivered a string in binary code - in this way, you can create sounds according to your needs. Connecting the beeper is fairly simple: one pin is connected to the mass, and the other to the microcontroller pin through a capacitor, as shown on the following image.

As with a button, you can employ a macro that will deliver a BEEP ROUTINE into a program when needed. Macro BEEP has two arguments:

BEEP macro  freq , duration:

freq:  frequency of the sound. The higher number produces higher frequency
duration:  sound duration. Higher the number, longer the sound.

Example 1: BEEP 0xFF, 0x02

The output has the highest frequency and duration at 2 cycles per 65.3mS which gives 130.6 mS

Example2: BEEP 0x90, 0x05

The output has a frequency of 0x90 and duration of 5 cycles per 65.3mS. It is best to determine these macro parameters through experimentation and select the sound that best suits the application.

The following is the BEEP Macro listing:

BEEP     MACRO    FREQ, DURATION
        MOVLW   FREQ
        MOVWF   BEEP_TEMP1
        MOVLW   DURATION
        CALL  BEEPSUB 
        ENDM


BEEPINIT MACRO
        BCF    BEEPPORT 
        BSF STATUS, RPO
        BCF BEEPTRIS 
        BCF    STATUS,RPO 
        ENDM


BEEPSUB MOVWF BEEP_TEMP2;SET THE  SOUND DURATION 
        CLRF  TMRO              ;INITIALIZE  THE   COUNTER
        BCF     BEEPPORT 
        BSF     STATUS,RPO 
        BCF     BEEPPORT 
        MOVLW  PRESCBEEP    ;SET PRESCALER  FOR THRO 
        MOVWF   OPTION_REG ; OPTION <-  U 
        BCF STATUS,RPO
 
BEEPA       
        BCF INTC0N,T0IF;CLEAR THRO  OVERFLORA  FLAG 
BEEPB       
        BSF   BEEPPORT
        CALL B_WAIT          ;DURATION OF  LOGICAL   "1"
        BCF   BEEPPORT
        CALL B_WAIT          ;DURATION OF  LOGICAL   "0"
        BTFSS   INTCON,TOIF;CHECK THRO  OVERFLORA  FLAG, 
        GOTO    BEEPB            ;SKIP  IF  SET
        DECFSZ BEEP_TEMP2,1 ;IS BEEP_TEHP2  =  0   ? 
        GOTO     BEEPA            ;IF NOT,   JUMP BACK  TO BEEP
        RETURN

B_WAIT 
        MOVFW BEEP_TEMP1 
        MOVWF   BEEP_TEMP3
B_WAITA  
        DECFSZ    BEEP_TEMP3,1 
        GOTO     B_WAITA
        RETURN
      
      

The following example shows the use of a macro in a program. The program produces two melodies which are obtained by pressing T1 or T2. Some of the previously discussed macros are included in the program.

    PROCESSOR  16f84
    #include "P16F84.inc"

    __CONFIG _CP_0FF  &  _WDT_0FF  &  _PWRTE_0N   &  _XT_0SC

Cblock    OxOC                             ;RAM strating address
PRESCraait
Beep_TEHPl                                 ;Belongs  to macro  "BEEP"
Beep_TEHP2
Beep_TEHP3
HIcnt                                           ;Auxiliary variable  for macro pausems
LOcnt
LOOPcnt
endc

#define BEEPport PORTA,3                   ;Port and pin beeper  is  located at
if define BEEPtris THIS A, 3

ORG        0x00                                ;Reset vector
goto     Main
ORG        0x04                                ; Interrupt vector
goto     Main                                ;no  intertupt routine

include  "Romux_lib.inc" 
include  "button. inc " 
include  "beep. i nc " 

Main                                                          ;Beginning of  the program
        banksel TRISA
        movlw   b'00010111                    initializing port A
        ncvwf   TRISA                   "          ;TRISA <-  0x17
        banksel  POSTB
Loop
        BEEPinit                                     ;Initialising Beeper
        button PORTA,   0,0,   Playl   ;Button 1
        button PORTA,   1,0,   Play2   ;Button 2
        goto      Loop Playl
        BEEP  OxFF,    0x02
        BEEP  0x90,    0x05
        BEEP  OxCO,    0x03
        BEEP  OxFF,   0x03                       ;First tune
        goto  Loop PI ay 2
        BEEP  Oxbb,   0x02
        BEEP  0x87,    0x05
        BEEP  0xa2,   0x03
        BEEP  0x98,   0x03                       ;Second tune
        goto  Loop
End                                               ;End of program      
      

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