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) :