PIC Processor's - Using Interrupts

So you've read the conceptual tutorial on interrupts and get the general idea. So let's get down to the practical stuff!

I'm using the 16F630 for this one. If you don't have that particular PIC, the general principles will apply, but it won't compile as-is.

As usual, here's the entire code up front:

;Anthony Rogers ;Oct 19th, 05 ;TgglIntF630 - Interrupt Demo list p=16F630 ; list directive to define processor #include <p16F630.inc> ; processor specific variable definitions __CONFIG _CP_OFF & _CPD_OFF & _BODEN_OFF & _MCLRE_OFF & _WDT_OFF & _PWRTE_ON & _INTRC_OSC_NOCLKOUT INT_VAR UDATA_SHR 0x20 w_temp RES 1 ; variable used for context saving status_temp RES 1 ; variable used for context saving ;********************************************************************** RESET_VECTOR CODE 0x000 ; processor reset vector goto main ; go to beginning of program INT_VECTOR CODE 0x004 ; interrupt vector location movwf w_temp ; save off current W register contents movf STATUS,w ; move status register into W register movwf status_temp ; save off contents of STATUS register bcf INTCON, INTF ;clear interrupt incf PORTC, f movf status_temp,w ; retrieve copy of STATUS register movwf STATUS ; restore pre-isr STATUS register contents swapf w_temp,f swapf w_temp,w ; restore pre-isr W register contents retfie ; return from interrupt main call 0x3FF ; retrieve factory calibration value bsf STATUS,RP0 ; set file register bank to 1 movwf OSCCAL ; update register with factory cal value movlw 0x00 ; initialize TRISC to output movwf TRISC movlw b'00000100' ; set PORTA, bit 3 (aka PORTA<3>) to input movwf TRISA bcf STATUS,RP0 ; set file register bank to 0 movlw b'00000111' ; setting CMCON<2:0> to 1 puts the comparator module in movwf CMCON ; "off" mode, allowing us to use PORTA<2> as digital input bsf INTCON, INTE ; enable External Interrupt bsf INTCON, GIE ; enable interrupts globally loop goto loop ; loop & wait... END ; directive 'end of program'

 

TO DO: Annotate Code

Circuit notes: > R1 can be a smaller value for more brightness - just keep it above 100 ohms or so. > R2 is a pullup resistor, and can be any value between 1K and 1M. > C1's value is not critical either - it's purpose is to simply filter out mechanical noise from the switch, and prevent the interrupt from triggering multiple time with one press.

 

 

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