Sunday, July 1, 2012

Melody door chime with "dead time"

Here's a very similar circuit and firmware to the door open/closed detector. However, instead of a magnetic contact (magnetic proximity switch) triggering the MCU to play the melody, it's an ordinary bell push for doorbells.

The "dead time" in the title refers to the time period after the melody is played when button presses are ignored. This discourages (but unfortunately does not prevent) pranksters (usually kids) from playing with the door chime. Also prevents impatient visitors/mailmen/couriers/extraterrestrials from making the chime go off continuously to put you into panic mode. Moreover, the circuit cannot be fooled by taping down the button in the hopes of forcing the circuit to keep playing the tune since the microcontroller only responds to edge triggering.

VR1 = L7812 +12V voltage regulator 1000mA
VR2 = 78L05ACZ +5V voltage regulator 100mA
MCU = Microchip PIC10F202 microcontroller
PB = bell push
OC1 = Avago HCPL-817 optoisolator
A1 = S9013 NPN transistor
BR = W01M 100V 1.5A bridge rectifier
XF = 220VAC to 6VAC transformer
SPKR = 8-ohm, 250mW, 3-inch speaker

The speaker is powered with 12VDC to significantly increase the output volume. As with the door status detector, I used an old computer speaker. PB is located several meters away from the circuit board. The internal weak pull-ups of the MCU are used so no external resistors are necessary on the collector of the optotransistor. I installed this circuit over three years ago and thus far I've not had any problems. Still working like a charm.

See the door open/closed detector for the principle of operation of the melody playing routines. Debounce routine works by storing the last eight readings in one 8-bit variable. Pushbutton is deemed not bouncing if the the variable is equal to 0x00 or 0xFF. Any other value means the switch is bouncing. Upon detection of a falling edge MCU plays the melody just once. To implement the dead time a simple one-second delay routine is called several times (depending on how many seconds is specified in the constant secdelay) after playing the tune and before handing back control to the pushbutton polling routine. When the melody is being played and during the dead time PB is not polled therefore button pushes are ignored. Because there's only one timer in the PC10F202, timer 0 is used for both playing the notes and for polling of the switches. The prescale values are different for the two applications and so OPTION register is edited accordingly when switching between the two. contains various defines and macro. 

; ********************************************************************************
; February 2009
; When bell push is momentarily pressed a melody is played.
; After the melody has finished there is a delay of 15 seconds when PB presses are ignored. 
; Because PB is not polled when melody is playing and during the delay,
; repeatedly pressing PB during this time does not result in any action.   
; Since the circuit responds only to edge triggering keeping the bell push depressed 
; will not result in any further action.
; MCU has debounce firmware that monitors bell push switch readings. Upon detection of a falling edge 
; MCU plays a sequence of musical notes. Firmware does not react to a rising edge. 
; MCU weak pull-ups are enabled in firmware. 
; Watchdog timer is activated. WDT nominal time-out according to datasheet is 18ms (without prescaler) 
; ********************************************************************************

    processor      10F202

    __config       _MCLRE_OFF & _CP_OFF & _WDT_ON
    cblock         0x08
CYCLES             ; determines how long the note sounds; value of 4 makes the note sound for approx 0.3sec
LENGTH:2           ; time the note will play
NOTE               ; note's T/2 in terms of TMR0 initial value
PB_VAL             ; each bit is a push button switch reading; bit0 has the latest reading; bits are shifted left during each TMR0 rollover
FEN                ; assortment of flag and enable bits for various purposes
COUNTER:3          ; loop counters
COUNTER2:2         ; loop counters

; ********************************************************************
    ; comment out when not debugging

    ; #define      debug
; ********************************************************************

    ifdef     debug
      #define     secdelay     .1
      #define     secdelay     .15     ; number of seconds after melody has ended before bell push can be pressed again for the chime to play again

    #define   spkr      GPIO,2    ; output speaker via NPN transistor
    #define   pb        GPIO,0    ; input from bell push

; macro for playing the note
    ; _note is the note's T/2 (half period)
    ; _length is the number of times the note is played 
key macro     _note, _length
    movlf     _note, NOTE
    movlf     _length, LENGTH
    call      PlayNote

; see wikipedia article "scientific pitch notation" for table of frequency values of notes
; B4 = ti = 493.88 Hz, period = 2.0248 ms, T/2 = 1.0124 us
; C5 = do = 523.25 Hz, period = 1.9111 ms, T/2 = 955.57 us
; D5 = re = 587.33 Hz, period = 1.7026 ms, T/2 = 851.31 us
; E5 = mi = 659.26 Hz, period = 1.5168 ms, T/2 = 758.43 us
; F5 = fa = 698.46 Hz, period = 1.4317 ms, T/2 = 715.86 us
; G5 = sol = 783.99 Hz, period = 1.2755 ms, T/2 = 637.76 us
; A5 = la = 880.00 Hz, period = 1.1364 ms, T/2 = 568.18 us
; B5 = ti = 987.77 Hz, period = 1.0124 ms, T/2 = 506.19 us
; C6 = do = 1046.5 Hz, period = 955.57 us, T/2 = 477.78 us
; D6 = re = 1174.7 Hz, period = 851.28 us, T/2 = 425.64 us
; E6 = mi = 1318.5 Hz, period = 758.44 us, T/2 = 379.22 us

; given internal clock = 4Mhz and timer0 prescaler = 1:4
; timer zero rolls over to zero every 1microsecond x 4 x TMR0 steps
; TMR0 steps = (T/2) / (1 us x 4)
; TMR0 initial value = 256 - TMR0 steps
; the following values should be loaded into TMR0 in order to produce the above notes, respectively
    #define   B4   .256 - .253
    #define   C5   .256 - .239
    #define   D5   .256 - .213
    #define   E5   .256 - .190
    #define   F5   .256 - .179
    #define   G5   .256 - .159
    #define   A5   .256 - .142
    #define   B5   .256 - .127
    #define   C6   .256 - .119
    #define   D6   .256 - .106
    #define   E6   .256 - .95

; in the PlayNote subroutine LENGTH determines how many times the note will play.
; since T/2 for every note is different LENGTH must be different in order for each note to play for the same length of time 
; LENGTH is computed as follows: L1 x T1 = L2 x T2 
; where L1 = length note 1, T1 = period of note 1, L2 = length of note 2, T2 = period of note2
; arbitrarily set LENGTH for E6 = 200 (leave room for a few more higher notes)
    #define   LB4  .75
    #define   LC5  .79
    #define   LD5  .89
    #define   LE5  .100
    #define   LF5  .106
    #define   LG5  .119
    #define   LA5  .133
    #define   LB5  .150
    #define   LC6  .159
    #define   LD6  .178
    #define   LE6  .200

    #define   pb_level  FEN,0     ; voltage level: 1 = hi, 0 = low 

    #define   option_poll_sw b'10000011'    ; value to copy to OPTION register when polling switches
                                            ; pullups enabled, prescaler to timer0, prescaler = 1:16  

    #define   option_chime   b'10000001'    ; value to copy to OPTION register in chime routine 
                                            ; pullups enabled, prescaler to timer0, prescaler = 1:4 

    #define   option_no_wpu  b'11000011'    ; value to copy to OPTION register when polling switches but with weak pull-ups off
    #define   tmr_init_val   .11            ; initial value for timer0, given 4Mhz clock and prescaler 1:16, TMR0 will rollover every 3.92ms

    org       0x0
    movwf     OSCCAL    ; calibrate the chip 
    goto      initialize
; =======================================================================================
;     subroutines
;     10F202 can only call subroutines if they are located in first 256 memory locations
; =======================================================================================

; ---------------------------------------------------------------------------------
; Notes are played by switching the speaker on and off at the frequency of the note. 
; the following routine also plays the note for a specified time as determined by LENGTH and CYCLES
    movff     NOTE, TMR0
    movff     LENGTH, LENGTH+1
    movff     CYCLES, COUNTER
    bsf       spkr
    dnxnotzero     TMR0     
    goto      loop_note
    movff     NOTE, TMR0
    toggle    spkr
    decfsz    LENGTH+1,f
    goto      loop_note
    movff     LENGTH, LENGTH+1
    decfsz    COUNTER,f
    goto      loop_note
    bcf       spkr
; ---------------------------------------------------------------------------------

; ---------------------------------------------------------------------------------
    movlw     option_chime     
; ---------------------------------------------------------------------------------

; ---------------------------------------------------------------------------------
    movlw     option_poll_sw
; ---------------------------------------------------------------------------------

; ---------------------------------------------------------------------------------
; approximately one second delay
    clrf      COUNTER
    clrf      COUNTER+1
    movlf     .5, COUNTER+2
    decfsz    COUNTER,f
    goto      delay1sec_loop
    decfsz    COUNTER+1,f
    goto      delay1sec_loop
    decfsz    COUNTER+2,f
    goto      delay1sec_loop
; ---------------------------------------------------------------------------------

; ---------------------------------------------------------------------------------
; the following melody is played when bell push is pressed (falling edge detected)
    call      OptionChime
    movlf     .4, CYCLES

    ; melody from the movie Close Encounters of the Third Kind
    ; --------------------------------------------------------
    key       D6, LD6
    key       E6, LE6
    key       C6, LC6
    key       E5, LE5
    key       G5, .255

    ; time interval when chime has already finished playing  
    ; and button presses are ignored
    movlf     secdelay, COUNTER2
    call      Delay_onesec
    decfsz    COUNTER2,f
    goto      $-2

    call      OptionPollSw
; ---------------------------------------------------------------------------------

; =======================================================================================
;     main program
; =======================================================================================

; ---------------------------------------------------------------------------------
    movlw     b'1'
    tris      GPIO
    call      OptionPollSw

    clrf      GPIO                ; speaker off
    movlf     0xFF, PB_VAL        ; all bits hi, pb contacts considered open
    bsf       pb_level            ; level = hi, pb contacts considered open
    movlf     tmr_init_val, TMR0      

; ---------------------------------------------------------------------------------

    dnxnotzero     TMR0      ; poll TMR0 until it rolls over
    goto      poll_timer0
    movlf     tmr_init_val, TMR0

; poll and check bell push; store value in 8-bit record
; if PB_VAL = 0xFF AND pb_level = 0 then let pb_level = 1, this is a rising edge detect, do nothing
; if PB_VAL = 0x0 AND pb_level = 1 then let pb_level = 0, this is a falling edge detect and chime is sounded
; if PB_VAL > 0 AND PB_VAL < 0xFF then switch is bouncing, so do nothing 
; if PB_VAL = 0xFF AND pb_level = 1 then there is no level change, so do nothing
; if PB_VAL = 0 AND pb_level = 0 then there is no level change, so do nothing 
    rlf       PB_VAL,f       ; discard oldest switch reading
    bcf       PB_VAL,0       ; carry bit will be moved into bit zero so clear bit0 
    dnxbit1   pb
    bsf       PB_VAL,0

    dnxeqlit  PB_VAL, 0xFF
    goto      all_bits_hi
    dnxzero   PB_VAL
    goto      all_bits_lo
    goto      check_pb_end
    dnxbit1   pb_level
    goto      check_pb_end
    bsf       pb_level       ; rising edge detected
    goto      check_pb_end
    dnxbit0   pb_level
    goto      check_pb_end
    bcf       pb_level       ; falling edge detected
    call      SoundChime

    goto      main
; ---------------------------------------------------------------------------------


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