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A PIC16F84A Alarm Clock

Samir school alarm clock

Photo : credits to Samir who built this clock

Here is a simple PIC16F84A alarm clock. This page summarizes this discussion (in french) in my forum, where Samir (aka numerique1) requested for help to build a weekly alarm clock for his school. Many thanks to him for his tests and patience.

This clock counts seconds, minutes, hours and day of the week.
Time is displayed on 4 seven segment LED displays, and is adjustable with three buttons at start time (up, down, enter).
You can program the day of the week, hour, minute and duration of the alarms.
The number of alarms are limited by ROM space only.
The alarm is on the RA4 open collector output of the PIC, and is repeated on a decimal point of the display.

For once, the program is in BASIC (mikroBasic) and I hope it will make a good start for beginners.


First, the BASIC source code.

Note that you can build it either for common cathod or common anode LED display.

'******************************************************************************
' PIC16F84A ALARM CLOCK
'******************************************************************************
'
' feel free to use this code at your own risks
'
' target : PIC16F84A, 16 Mhz crystal
' HS clock, no watchdog.
'
' Author : Bruno Gavand, September 2007
' see more details on http://www.micro-examples.com/
'
'******************************************************************************

program alarmClock

'
' if you are using COMMON CATHODE LED display, uncomment this definition.
' if you are using COMMON ANODE LED display, comment this definition.
'
'#define CATHODE_COMMUNE

symbol  LUNDI           = 0     ' monday
symbol  MARDI           = 1     ' thuesday
symbol  MERCREDI        = 2     ' wednesday
symbol  JEUDI           = 3     ' thursday
symbol  VENDREDI        = 4     ' friday
symbol  SAMEDI          = 5     ' saturday
symbol  DIMANCHE        = 6     ' sunday
symbol  LMMJV           = 7     ' from monday to friday included

'
' alarm definitions, to be changed on your needs
'
symbol  NBALARM         = 16    ' number of programmed alarms

const   alarmTable   as byte[NBALARM * 4] = (
'       JOUR            HEURE   MINUTE  DUREE (secondes, 59 maxi)
'       DAY             HOUR    MINUTE  DURATION (in seconds, max is 59)
        LUNDI,          8,      30,     10,
        LUNDI,          12,     30,     10,
        LUNDI,          14,     00,     10,
        LUNDI,          16,     30,     10,
        MARDI,          8,      30,     10,
        MARDI,          12,     30,     10,
        MARDI,          14,     00,     10,
        MARDI,          16,     30,     10,
        JEUDI,          8,      30,     10,
        JEUDI,          12,     30,     10,
        JEUDI,          14,     00,     10,
        JEUDI,          16,     30,     10,
        VENDREDI,       8,      30,     10,
        VENDREDI,       12,     30,     10,
        VENDREDI,       14,     00,     10,
        VENDREDI,       16,     30,     10
        )

dim maxcount    as word         ' number of TMR0 overflow per second
dim scaler      as word         ' RTC scaler
dim jj          as byte         ' day of week, 0 is monday
dim hh          as byte         ' hour
dim mn          as byte         ' min
dim ss          as byte         ' sec
dim digiled     as byte[4]      ' 4 x 7 segment table
dim digit       as byte         ' number of current digit to be displayed
dim dp          as byte         ' decimal point
dim key         as byte         ' key code
dim alarm       as byte         ' alarm flag

'
' the ISR works as real time clock
'
sub procedure interrupt
        dim i as byte

'
' count time
'
        scaler = scaler + 1
        if scaler > maxcount
        then
                scaler = 0

                inc(ss)
                if ss = 60
                then
                        ss = 0
                        inc(mn)
                        if mn = 60
                        then
                                mn = 0
                                inc(hh)
                                if hh = 24
                                then
                                        hh = 0
                                        inc(jj)
                                        if jj = 8
                                        then
                                                jj = 1
                                        end if
                                end if
                        end if
                end if
        end if

'
' LED display
'
#ifdef CATHODE_COMMUNE
        PORTA = PORTA and $f0
        TRISA = $0f
        key = PORTA
        TRISA = 0
        PORTB = 0
#else
        PORTA = PORTA or $0f
        TRISA = $0f
        key = PORTA
        key = not(key)
        TRISA = 0
        PORTB = $ff
#endif
        key = key and $07

        digit = digit + 1

        if digit > 3
        then
                digit = 0
                i = $01
        else
                i = $01 << digit
        end if

#ifdef CATHODE_COMMUNE
        PORTB = digiled[digit]
        PORTA = PORTA or i
#else
        PORTB = digiled[digit]
        PORTB = not(PORTB)
        PORTA = PORTA and not(i)
#endif

        INTCON.T0IF = 0
end sub

'
' converts digit to 7 segment
'
sub function intTo7seg(dim n as byte) as byte
        select case n
                case 0  result = $3F
                case 1  result = $06
                case 2  result = $5B
                case 3  result = $4F
                case 4  result = $66
                case 5  result = $6D
                case 6  result = $7D
                case 7  result = $07
                case 8  result = $7F
                case 9  result = $6F
        end select
end sub

'
' select a value with keys
' value is pointed to by v, display char s as header, maximum value is max
'
sub procedure setValue(dim v as ^byte, dim s as byte, dim max as byte)
        digiled[0] = s
        digiled[1] = 0

        while 1
                if key.0
                then
                        inc(v^)
                        if(v^ > max)
                        then
                                v^ = 0
                        end if
                end if

                if key.1
                then
                        if(v^ = 0)
                        then
                                v^ = max
                        else
                                dec(v^)
                        end if
                end if

                if key.2
                then
                        Delay_ms(50)
                        while key.2
                        wend
                        Delay_ms(50)
                        scaler = 0
                        ss = 0
                        return
                end if

                digiled[2] = intTo7seg(v^ / 10)
                digiled[3] = intTo7seg(v^ mod 10)

                delay_ms(300)
        wend
end sub

'
' program entry
'
main:
        dim i as byte

'
' init variables
'
        dp = 0

        hh = 0
        mn = 0
        ss = 0
        jj = 0

        maxcount = 15625

'
' init I/O
'
        PORTA = %00010000
        TRISA = %00000000

        PORTB = 0
        TRISB = $00

'
' init interrupts
'
        INTCON = %10100000
        OPTION_REG = %11011000

        Delay_ms(50)

'
' clock adjustment
'
        setValue(@hh, 116, 23)
        setValue(@mn, 55, 59)
        setValue(@jj, 14, 6)

'
' forever loop
'
        while true
                if key
                then
'
' display day and seconds (what for ? don't remember !)
'
                        digiled[0] = intTo7seg(jj)
                        digiled[1] = 0
                        digiled[2] = intTo7seg(ss / 10)
                        digiled[3] = intTo7seg(ss mod 10)
                else
'
' display hours and minutes
'
                        if hh < 10
                        then
                                digiled[0] = 0
                                digiled[1] = intTo7seg(hh)
                        else
                                digiled[0] = intTo7seg(hh / 10)
                                digiled[1] = intTo7seg(hh mod 10)
                        end if
                        digiled[2] = intTo7seg(mn / 10)
                        digiled[3] = intTo7seg(mn mod 10)
                end if

'
' blinks semicolon (or decimal point)
'
                if scaler > maxcount / 2
                then
                        dp.1 = 1
                else
                        dp.1 = 0
                end if

'
' set decimal points
'
                digiled[0].7 = dp.0
                digiled[1].7 = dp.1
                digiled[2].7 = dp.2
                digiled[3].7 = dp.3

'
' check for alarm condition
'
                alarm = 0
                for i = 0 to (NBALARM - 1) * 4
                        if ((alarmTable[i] = jj) or ((alarmTable[i] = LMMJV) and (jj < SAMEDI)))
                                        and (alarmTable[i + 1] = hh)
                                        and (alarmTable[i + 2] = mn)
                                        and (alarmTable[i + 3] > ss)
                        then
                                inc(alarm)
                        end if
                next i

                if alarm
                then
'
' set alarm
'
                        dp.3 = 1
                        PORTA.4 = 0
                else
'
' clear alarm
'
                        dp.3 = 0
                        PORTA.4 = 1
                end if
        wend
end.

Here is the circuit schematic (click on the picture to get a full sized image) :

PIC16F84A alarm clock schematic